29 files changed, 15683 insertions, 0 deletions

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 4d8d90b4fe78..3bfc8f1da9fe 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -174,6 +174,8 @@ config MD_FAULTY
 
           In unsure, say N.
 
+source "drivers/md/bcache/Kconfig"
+
 config BLK_DEV_DM
         tristate "Device mapper support"
         ---help---
diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index 7ceeaefc0e95..1439fd4ad9b1 100644
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -29,6 +29,7 @@ obj-$(CONFIG_MD_RAID10)		+= raid10.o
 obj-$(CONFIG_MD_RAID456)        += raid456.o
 obj-$(CONFIG_MD_MULTIPATH)      += multipath.o
 obj-$(CONFIG_MD_FAULTY)         += faulty.o
+obj-$(CONFIG_BCACHE)            += bcache/
 obj-$(CONFIG_BLK_DEV_MD)        += md-mod.o
 obj-$(CONFIG_BLK_DEV_DM)        += dm-mod.o
 obj-$(CONFIG_DM_BUFIO)          += dm-bufio.o
diff --git a/drivers/md/bcache/Kconfig b/drivers/md/bcache/Kconfig
new file mode 100644
index 000000000000..05c220d05e23
--- /dev/null
+++ b/drivers/md/bcache/Kconfig
@@ -0,0 +1,42 @@
+
+config BCACHE
+        tristate "Block device as cache"
+        select CLOSURES
+        ---help---
+        Allows a block device to be used as cache for other devices; uses
+        a btree for indexing and the layout is optimized for SSDs.
+
+        See Documentation/bcache.txt for details.
+
+config BCACHE_DEBUG
+        bool "Bcache debugging"
+        depends on BCACHE
+        ---help---
+        Don't select this option unless you're a developer
+
+        Enables extra debugging tools (primarily a fuzz tester)
+
+config BCACHE_EDEBUG
+        bool "Extended runtime checks"
+        depends on BCACHE
+        ---help---
+        Don't select this option unless you're a developer
+
+        Enables extra runtime checks which significantly affect performance
+
+config BCACHE_CLOSURES_DEBUG
+        bool "Debug closures"
+        depends on BCACHE
+        select DEBUG_FS
+        ---help---
+        Keeps all active closures in a linked list and provides a debugfs
+        interface to list them, which makes it possible to see asynchronous
+        operations that get stuck.
+
+# cgroup code needs to be updated:
+#
+#config CGROUP_BCACHE
+#       bool "Cgroup controls for bcache"
+#       depends on BCACHE && BLK_CGROUP
+#       ---help---
+#       TODO
diff --git a/drivers/md/bcache/Makefile b/drivers/md/bcache/Makefile
new file mode 100644
index 000000000000..0e9c82523be6
--- /dev/null
+++ b/drivers/md/bcache/Makefile
@@ -0,0 +1,7 @@
+
+obj-$(CONFIG_BCACHE)    += bcache.o
+
+bcache-y                := alloc.o btree.o bset.o io.o journal.o writeback.o\
+        movinggc.o request.o super.o sysfs.o debug.o util.o trace.o stats.o closure.o
+
+CFLAGS_request.o        += -Iblock
diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
new file mode 100644
index 000000000000..ed18115e078e
--- /dev/null
+++ b/drivers/md/bcache/alloc.c
@@ -0,0 +1,583 @@
+/*
+ * Primary bucket allocation code
+ *
+ * Copyright 2012 Google, Inc.
+ *
+ * Allocation in bcache is done in terms of buckets:
+ *
+ * Each bucket has associated an 8 bit gen; this gen corresponds to the gen in
+ * btree pointers - they must match for the pointer to be considered valid.
+ *
+ * Thus (assuming a bucket has no dirty data or metadata in it) we can reuse a
+ * bucket simply by incrementing its gen.
+ *
+ * The gens (along with the priorities; it's really the gens are important but
+ * the code is named as if it's the priorities) are written in an arbitrary list
+ * of buckets on disk, with a pointer to them in the journal header.
+ *
+ * When we invalidate a bucket, we have to write its new gen to disk and wait
+ * for that write to complete before we use it - otherwise after a crash we
+ * could have pointers that appeared to be good but pointed to data that had
+ * been overwritten.
+ *
+ * Since the gens and priorities are all stored contiguously on disk, we can
+ * batch this up: We fill up the free_inc list with freshly invalidated buckets,
+ * call prio_write(), and when prio_write() finishes we pull buckets off the
+ * free_inc list and optionally discard them.
+ *
+ * free_inc isn't the only freelist - if it was, we'd often to sleep while
+ * priorities and gens were being written before we could allocate. c->free is a
+ * smaller freelist, and buckets on that list are always ready to be used.
+ *
+ * If we've got discards enabled, that happens when a bucket moves from the
+ * free_inc list to the free list.
+ *
+ * There is another freelist, because sometimes we have buckets that we know
+ * have nothing pointing into them - these we can reuse without waiting for
+ * priorities to be rewritten. These come from freed btree nodes and buckets
+ * that garbage collection discovered no longer had valid keys pointing into
+ * them (because they were overwritten). That's the unused list - buckets on the
+ * unused list move to the free list, optionally being discarded in the process.
+ *
+ * It's also important to ensure that gens don't wrap around - with respect to
+ * either the oldest gen in the btree or the gen on disk. This is quite
+ * difficult to do in practice, but we explicitly guard against it anyways - if
+ * a bucket is in danger of wrapping around we simply skip invalidating it that
+ * time around, and we garbage collect or rewrite the priorities sooner than we
+ * would have otherwise.
+ *
+ * bch_bucket_alloc() allocates a single bucket from a specific cache.
+ *
+ * bch_bucket_alloc_set() allocates one or more buckets from different caches
+ * out of a cache set.
+ *
+ * free_some_buckets() drives all the processes described above. It's called
+ * from bch_bucket_alloc() and a few other places that need to make sure free
+ * buckets are ready.
+ *
+ * invalidate_buckets_(lru|fifo)() find buckets that are available to be
+ * invalidated, and then invalidate them and stick them on the free_inc list -
+ * in either lru or fifo order.
+ */
+
+#include "bcache.h"
+#include "btree.h"
+
+#include <linux/random.h>
+
+#define MAX_IN_FLIGHT_DISCARDS          8U
+
+/* Bucket heap / gen */
+
+uint8_t bch_inc_gen(struct cache *ca, struct bucket *b)
+{
+        uint8_t ret = ++b->gen;
+
+        ca->set->need_gc = max(ca->set->need_gc, bucket_gc_gen(b));
+        WARN_ON_ONCE(ca->set->need_gc > BUCKET_GC_GEN_MAX);
+
+        if (CACHE_SYNC(&ca->set->sb)) {
+                ca->need_save_prio = max(ca->need_save_prio,
+                                         bucket_disk_gen(b));
+                WARN_ON_ONCE(ca->need_save_prio > BUCKET_DISK_GEN_MAX);
+        }
+
+        return ret;
+}
+
+void bch_rescale_priorities(struct cache_set *c, int sectors)
+{
+        struct cache *ca;
+        struct bucket *b;
+        unsigned next = c->nbuckets * c->sb.bucket_size / 1024;
+        unsigned i;
+        int r;
+
+        atomic_sub(sectors, &c->rescale);
+
+        do {
+                r = atomic_read(&c->rescale);
+
+                if (r >= 0)
+                        return;
+        } while (atomic_cmpxchg(&c->rescale, r, r + next) != r);
+
+        mutex_lock(&c->bucket_lock);
+
+        c->min_prio = USHRT_MAX;
+
+        for_each_cache(ca, c, i)
+                for_each_bucket(b, ca)
+                        if (b->prio &&
+                            b->prio != BTREE_PRIO &&
+                            !atomic_read(&b->pin)) {
+                                b->prio--;
+                                c->min_prio = min(c->min_prio, b->prio);
+                        }
+
+        mutex_unlock(&c->bucket_lock);
+}
+
+/* Discard/TRIM */
+
+struct discard {
+        struct list_head        list;
+        struct work_struct      work;
+        struct cache            *ca;
+        long                    bucket;
+
+        struct bio              bio;
+        struct bio_vec          bv;
+};
+
+static void discard_finish(struct work_struct *w)
+{
+        struct discard *d = container_of(w, struct discard, work);
+        struct cache *ca = d->ca;
+        char buf[BDEVNAME_SIZE];
+
+        if (!test_bit(BIO_UPTODATE, &d->bio.bi_flags)) {
+                pr_notice("discard error on %s, disabling",
+                         bdevname(ca->bdev, buf));
+                d->ca->discard = 0;
+        }
+
+        mutex_lock(&ca->set->bucket_lock);
+
+        fifo_push(&ca->free, d->bucket);
+        list_add(&d->list, &ca->discards);
+        atomic_dec(&ca->discards_in_flight);
+
+        mutex_unlock(&ca->set->bucket_lock);
+
+        closure_wake_up(&ca->set->bucket_wait);
+        wake_up(&ca->set->alloc_wait);
+
+        closure_put(&ca->set->cl);
+}
+
+static void discard_endio(struct bio *bio, int error)
+{
+        struct discard *d = container_of(bio, struct discard, bio);
+        schedule_work(&d->work);
+}
+
+static void do_discard(struct cache *ca, long bucket)
+{
+        struct discard *d = list_first_entry(&ca->discards,
+                                             struct discard, list);
+
+        list_del(&d->list);
+        d->bucket = bucket;
+
+        atomic_inc(&ca->discards_in_flight);
+        closure_get(&ca->set->cl);
+
+        bio_init(&d->bio);
+
+        d->bio.bi_sector        = bucket_to_sector(ca->set, d->bucket);
+        d->bio.bi_bdev          = ca->bdev;
+        d->bio.bi_rw            = REQ_WRITE|REQ_DISCARD;
+        d->bio.bi_max_vecs      = 1;
+        d->bio.bi_io_vec        = d->bio.bi_inline_vecs;
+        d->bio.bi_size          = bucket_bytes(ca);
+        d->bio.bi_end_io        = discard_endio;
+        bio_set_prio(&d->bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
+
+        submit_bio(0, &d->bio);
+}
+
+/* Allocation */
+
+static inline bool can_inc_bucket_gen(struct bucket *b)
+{
+        return bucket_gc_gen(b) < BUCKET_GC_GEN_MAX &&
+                bucket_disk_gen(b) < BUCKET_DISK_GEN_MAX;
+}
+
+bool bch_bucket_add_unused(struct cache *ca, struct bucket *b)
+{
+        BUG_ON(GC_MARK(b) || GC_SECTORS_USED(b));
+
+        if (fifo_used(&ca->free) > ca->watermark[WATERMARK_MOVINGGC] &&
+            CACHE_REPLACEMENT(&ca->sb) == CACHE_REPLACEMENT_FIFO)
+                return false;
+
+        b->prio = 0;
+
+        if (can_inc_bucket_gen(b) &&
+            fifo_push(&ca->unused, b - ca->buckets)) {
+                atomic_inc(&b->pin);
+                return true;
+        }
+
+        return false;
+}
+
+static bool can_invalidate_bucket(struct cache *ca, struct bucket *b)
+{
+        return GC_MARK(b) == GC_MARK_RECLAIMABLE &&
+                !atomic_read(&b->pin) &&
+                can_inc_bucket_gen(b);
+}
+
+static void invalidate_one_bucket(struct cache *ca, struct bucket *b)
+{
+        bch_inc_gen(ca, b);
+        b->prio = INITIAL_PRIO;
+        atomic_inc(&b->pin);
+        fifo_push(&ca->free_inc, b - ca->buckets);
+}
+
+static void invalidate_buckets_lru(struct cache *ca)
+{
+        unsigned bucket_prio(struct bucket *b)
+        {
+                return ((unsigned) (b->prio - ca->set->min_prio)) *
+                        GC_SECTORS_USED(b);
+        }
+
+        bool bucket_max_cmp(struct bucket *l, struct bucket *r)
+        {
+                return bucket_prio(l) < bucket_prio(r);
+        }
+
+        bool bucket_min_cmp(struct bucket *l, struct bucket *r)
+        {
+                return bucket_prio(l) > bucket_prio(r);
+        }
+
+        struct bucket *b;
+        ssize_t i;
+
+        ca->heap.used = 0;
+
+        for_each_bucket(b, ca) {
+                if (!can_invalidate_bucket(ca, b))
+                        continue;
+
+                if (!GC_SECTORS_USED(b)) {
+                        if (!bch_bucket_add_unused(ca, b))
+                                return;
+                } else {
+                        if (!heap_full(&ca->heap))
+                                heap_add(&ca->heap, b, bucket_max_cmp);
+                        else if (bucket_max_cmp(b, heap_peek(&ca->heap))) {
+                                ca->heap.data[0] = b;
+                                heap_sift(&ca->heap, 0, bucket_max_cmp);
+                        }
+                }
+        }
+
+        if (ca->heap.used * 2 < ca->heap.size)
+                bch_queue_gc(ca->set);
+
+        for (i = ca->heap.used / 2 - 1; i >= 0; --i)
+                heap_sift(&ca->heap, i, bucket_min_cmp);
+
+        while (!fifo_full(&ca->free_inc)) {
+                if (!heap_pop(&ca->heap, b, bucket_min_cmp)) {
+                        /* We don't want to be calling invalidate_buckets()
+                         * multiple times when it can't do anything
+                         */
+                        ca->invalidate_needs_gc = 1;
+                        bch_queue_gc(ca->set);
+                        return;
+                }
+
+                invalidate_one_bucket(ca, b);
+        }
+}
+
+static void invalidate_buckets_fifo(struct cache *ca)
+{
+        struct bucket *b;
+        size_t checked = 0;
+
+        while (!fifo_full(&ca->free_inc)) {
+                if (ca->fifo_last_bucket <  ca->sb.first_bucket ||
+                    ca->fifo_last_bucket >= ca->sb.nbuckets)
+                        ca->fifo_last_bucket = ca->sb.first_bucket;
+
+                b = ca->buckets + ca->fifo_last_bucket++;
+
+                if (can_invalidate_bucket(ca, b))
+                        invalidate_one_bucket(ca, b);
+
+                if (++checked >= ca->sb.nbuckets) {
+                        ca->invalidate_needs_gc = 1;
+                        bch_queue_gc(ca->set);
+                        return;
+                }
+        }
+}
+
+static void invalidate_buckets_random(struct cache *ca)
+{
+        struct bucket *b;
+        size_t checked = 0;
+
+        while (!fifo_full(&ca->free_inc)) {
+                size_t n;
+                get_random_bytes(&n, sizeof(n));
+
+                n %= (size_t) (ca->sb.nbuckets - ca->sb.first_bucket);
+                n += ca->sb.first_bucket;
+
+                b = ca->buckets + n;
+
+                if (can_invalidate_bucket(ca, b))
+                        invalidate_one_bucket(ca, b);
+
+                if (++checked >= ca->sb.nbuckets / 2) {
+                        ca->invalidate_needs_gc = 1;
+                        bch_queue_gc(ca->set);
+                        return;
+                }
+        }
+}
+
+static void invalidate_buckets(struct cache *ca)
+{
+        if (ca->invalidate_needs_gc)
+                return;
+
+        switch (CACHE_REPLACEMENT(&ca->sb)) {
+        case CACHE_REPLACEMENT_LRU:
+                invalidate_buckets_lru(ca);
+                break;
+        case CACHE_REPLACEMENT_FIFO:
+                invalidate_buckets_fifo(ca);
+                break;
+        case CACHE_REPLACEMENT_RANDOM:
+                invalidate_buckets_random(ca);
+                break;
+        }
+}
+
+#define allocator_wait(ca, cond)                                        \
+do {                                                                    \
+        DEFINE_WAIT(__wait);                                            \
+                                                                        \
+        while (!(cond)) {                                               \
+                prepare_to_wait(&ca->set->alloc_wait,                   \
+                                &__wait, TASK_INTERRUPTIBLE);           \
+                                                                        \
+                mutex_unlock(&(ca)->set->bucket_lock);                  \
+                if (test_bit(CACHE_SET_STOPPING_2, &ca->set->flags)) {  \
+                        finish_wait(&ca->set->alloc_wait, &__wait);     \
+                        closure_return(cl);                             \
+                }                                                       \
+                                                                        \
+                schedule();                                             \
+                __set_current_state(TASK_RUNNING);                      \
+                mutex_lock(&(ca)->set->bucket_lock);                    \
+        }                                                               \
+                                                                        \
+        finish_wait(&ca->set->alloc_wait, &__wait);                     \
+} while (0)
+
+void bch_allocator_thread(struct closure *cl)
+{
+        struct cache *ca = container_of(cl, struct cache, alloc);
+
+        mutex_lock(&ca->set->bucket_lock);
+
+        while (1) {
+                while (1) {
+                        long bucket;
+
+                        if ((!atomic_read(&ca->set->prio_blocked) ||
+                             !CACHE_SYNC(&ca->set->sb)) &&
+                            !fifo_empty(&ca->unused))
+                                fifo_pop(&ca->unused, bucket);
+                        else if (!fifo_empty(&ca->free_inc))
+                                fifo_pop(&ca->free_inc, bucket);
+                        else
+                                break;
+
+                        allocator_wait(ca, (int) fifo_free(&ca->free) >
+                                       atomic_read(&ca->discards_in_flight));
+
+                        if (ca->discard) {
+                                allocator_wait(ca, !list_empty(&ca->discards));
+                                do_discard(ca, bucket);
+                        } else {
+                                fifo_push(&ca->free, bucket);
+                                closure_wake_up(&ca->set->bucket_wait);
+                        }
+                }
+
+                allocator_wait(ca, ca->set->gc_mark_valid);
+                invalidate_buckets(ca);
+
+                allocator_wait(ca, !atomic_read(&ca->set->prio_blocked) ||
+                               !CACHE_SYNC(&ca->set->sb));
+
+                if (CACHE_SYNC(&ca->set->sb) &&
+                    (!fifo_empty(&ca->free_inc) ||
+                     ca->need_save_prio > 64)) {
+                        bch_prio_write(ca);
+                }
+        }
+}
+
+long bch_bucket_alloc(struct cache *ca, unsigned watermark, struct closure *cl)
+{
+        long r = -1;
+again:
+        wake_up(&ca->set->alloc_wait);
+
+        if (fifo_used(&ca->free) > ca->watermark[watermark] &&
+            fifo_pop(&ca->free, r)) {
+                struct bucket *b = ca->buckets + r;
+#ifdef CONFIG_BCACHE_EDEBUG
+                size_t iter;
+                long i;
+
+                for (iter = 0; iter < prio_buckets(ca) * 2; iter++)
+                        BUG_ON(ca->prio_buckets[iter] == (uint64_t) r);
+
+                fifo_for_each(i, &ca->free, iter)
+                        BUG_ON(i == r);
+                fifo_for_each(i, &ca->free_inc, iter)
+                        BUG_ON(i == r);
+                fifo_for_each(i, &ca->unused, iter)
+                        BUG_ON(i == r);
+#endif
+                BUG_ON(atomic_read(&b->pin) != 1);
+
+                SET_GC_SECTORS_USED(b, ca->sb.bucket_size);
+
+                if (watermark <= WATERMARK_METADATA) {
+                        SET_GC_MARK(b, GC_MARK_METADATA);
+                        b->prio = BTREE_PRIO;
+                } else {
+                        SET_GC_MARK(b, GC_MARK_RECLAIMABLE);
+                        b->prio = INITIAL_PRIO;
+                }
+
+                return r;
+        }
+
+        pr_debug("alloc failure: blocked %i free %zu free_inc %zu unused %zu",
+                 atomic_read(&ca->set->prio_blocked), fifo_used(&ca->free),
+                 fifo_used(&ca->free_inc), fifo_used(&ca->unused));
+
+        if (cl) {
+                closure_wait(&ca->set->bucket_wait, cl);
+
+                if (closure_blocking(cl)) {
+                        mutex_unlock(&ca->set->bucket_lock);
+                        closure_sync(cl);
+                        mutex_lock(&ca->set->bucket_lock);
+                        goto again;
+                }
+        }
+
+        return -1;
+}
+
+void bch_bucket_free(struct cache_set *c, struct bkey *k)
+{
+        unsigned i;
+
+        for (i = 0; i < KEY_PTRS(k); i++) {
+                struct bucket *b = PTR_BUCKET(c, k, i);
+
+                SET_GC_MARK(b, 0);
+                SET_GC_SECTORS_USED(b, 0);
+                bch_bucket_add_unused(PTR_CACHE(c, k, i), b);
+        }
+}
+
+int __bch_bucket_alloc_set(struct cache_set *c, unsigned watermark,
+                           struct bkey *k, int n, struct closure *cl)
+{
+        int i;
+
+        lockdep_assert_held(&c->bucket_lock);
+        BUG_ON(!n || n > c->caches_loaded || n > 8);
+
+        bkey_init(k);
+
+        /* sort by free space/prio of oldest data in caches */
+
+        for (i = 0; i < n; i++) {
+                struct cache *ca = c->cache_by_alloc[i];
+                long b = bch_bucket_alloc(ca, watermark, cl);
+
+                if (b == -1)
+                        goto err;
+
+                k->ptr[i] = PTR(ca->buckets[b].gen,
+                                bucket_to_sector(c, b),
+                                ca->sb.nr_this_dev);
+
+                SET_KEY_PTRS(k, i + 1);
+        }
+
+        return 0;
+err:
+        bch_bucket_free(c, k);
+        __bkey_put(c, k);
+        return -1;
+}
+
+int bch_bucket_alloc_set(struct cache_set *c, unsigned watermark,
+                         struct bkey *k, int n, struct closure *cl)
+{
+        int ret;
+        mutex_lock(&c->bucket_lock);
+        ret = __bch_bucket_alloc_set(c, watermark, k, n, cl);
+        mutex_unlock(&c->bucket_lock);
+        return ret;
+}
+
+/* Init */
+
+void bch_cache_allocator_exit(struct cache *ca)
+{
+        struct discard *d;
+
+        while (!list_empty(&ca->discards)) {
+                d = list_first_entry(&ca->discards, struct discard, list);
+                cancel_work_sync(&d->work);
+                list_del(&d->list);
+                kfree(d);
+        }
+}
+
+int bch_cache_allocator_init(struct cache *ca)
+{
+        unsigned i;
+
+        /*
+         * Reserve:
+         * Prio/gen writes first
+         * Then 8 for btree allocations
+         * Then half for the moving garbage collector
+         */
+
+        ca->watermark[WATERMARK_PRIO] = 0;
+
+        ca->watermark[WATERMARK_METADATA] = prio_buckets(ca);
+
+        ca->watermark[WATERMARK_MOVINGGC] = 8 +
+                ca->watermark[WATERMARK_METADATA];
+
+        ca->watermark[WATERMARK_NONE] = ca->free.size / 2 +
+                ca->watermark[WATERMARK_MOVINGGC];
+
+        for (i = 0; i < MAX_IN_FLIGHT_DISCARDS; i++) {
+                struct discard *d = kzalloc(sizeof(*d), GFP_KERNEL);
+                if (!d)
+                        return -ENOMEM;
+
+                d->ca = ca;
+                INIT_WORK(&d->work, discard_finish);
+                list_add(&d->list, &ca->discards);
+        }
+
+        return 0;
+}
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
new file mode 100644
index 000000000000..d01a553f63f3
--- /dev/null
+++ b/drivers/md/bcache/bcache.h
@@ -0,0 +1,1232 @@
+#ifndef _BCACHE_H
+#define _BCACHE_H
+
+/*
+ * SOME HIGH LEVEL CODE DOCUMENTATION:
+ *
+ * Bcache mostly works with cache sets, cache devices, and backing devices.
+ *
+ * Support for multiple cache devices hasn't quite been finished off yet, but
+ * it's about 95% plumbed through. A cache set and its cache devices is sort of
+ * like a md raid array and its component devices. Most of the code doesn't care
+ * about individual cache devices, the main abstraction is the cache set.
+ *
+ * Multiple cache devices is intended to give us the ability to mirror dirty
+ * cached data and metadata, without mirroring clean cached data.
+ *
+ * Backing devices are different, in that they have a lifetime independent of a
+ * cache set. When you register a newly formatted backing device it'll come up
+ * in passthrough mode, and then you can attach and detach a backing device from
+ * a cache set at runtime - while it's mounted and in use. Detaching implicitly
+ * invalidates any cached data for that backing device.
+ *
+ * A cache set can have multiple (many) backing devices attached to it.
+ *
+ * There's also flash only volumes - this is the reason for the distinction
+ * between struct cached_dev and struct bcache_device. A flash only volume
+ * works much like a bcache device that has a backing device, except the
+ * "cached" data is always dirty. The end result is that we get thin
+ * provisioning with very little additional code.
+ *
+ * Flash only volumes work but they're not production ready because the moving
+ * garbage collector needs more work. More on that later.
+ *
+ * BUCKETS/ALLOCATION:
+ *
+ * Bcache is primarily designed for caching, which means that in normal
+ * operation all of our available space will be allocated. Thus, we need an
+ * efficient way of deleting things from the cache so we can write new things to
+ * it.
+ *
+ * To do this, we first divide the cache device up into buckets. A bucket is the
+ * unit of allocation; they're typically around 1 mb - anywhere from 128k to 2M+
+ * works efficiently.
+ *
+ * Each bucket has a 16 bit priority, and an 8 bit generation associated with
+ * it. The gens and priorities for all the buckets are stored contiguously and
+ * packed on disk (in a linked list of buckets - aside from the superblock, all
+ * of bcache's metadata is stored in buckets).
+ *
+ * The priority is used to implement an LRU. We reset a bucket's priority when
+ * we allocate it or on cache it, and every so often we decrement the priority
+ * of each bucket. It could be used to implement something more sophisticated,
+ * if anyone ever gets around to it.
+ *
+ * The generation is used for invalidating buckets. Each pointer also has an 8
+ * bit generation embedded in it; for a pointer to be considered valid, its gen
+ * must match the gen of the bucket it points into.  Thus, to reuse a bucket all
+ * we have to do is increment its gen (and write its new gen to disk; we batch
+ * this up).
+ *
+ * Bcache is entirely COW - we never write twice to a bucket, even buckets that
+ * contain metadata (including btree nodes).
+ *
+ * THE BTREE:
+ *
+ * Bcache is in large part design around the btree.
+ *
+ * At a high level, the btree is just an index of key -> ptr tuples.
+ *
+ * Keys represent extents, and thus have a size field. Keys also have a variable
+ * number of pointers attached to them (potentially zero, which is handy for
+ * invalidating the cache).
+ *
+ * The key itself is an inode:offset pair. The inode number corresponds to a
+ * backing device or a flash only volume. The offset is the ending offset of the
+ * extent within the inode - not the starting offset; this makes lookups
+ * slightly more convenient.
+ *
+ * Pointers contain the cache device id, the offset on that device, and an 8 bit
+ * generation number. More on the gen later.
+ *
+ * Index lookups are not fully abstracted - cache lookups in particular are
+ * still somewhat mixed in with the btree code, but things are headed in that
+ * direction.
+ *
+ * Updates are fairly well abstracted, though. There are two different ways of
+ * updating the btree; insert and replace.
+ *
+ * BTREE_INSERT will just take a list of keys and insert them into the btree -
+ * overwriting (possibly only partially) any extents they overlap with. This is
+ * used to update the index after a write.
+ *
+ * BTREE_REPLACE is really cmpxchg(); it inserts a key into the btree iff it is
+ * overwriting a key that matches another given key. This is used for inserting
+ * data into the cache after a cache miss, and for background writeback, and for
+ * the moving garbage collector.
+ *
+ * There is no "delete" operation; deleting things from the index is
+ * accomplished by either by invalidating pointers (by incrementing a bucket's
+ * gen) or by inserting a key with 0 pointers - which will overwrite anything
+ * previously present at that location in the index.
+ *
+ * This means that there are always stale/invalid keys in the btree. They're
+ * filtered out by the code that iterates through a btree node, and removed when
+ * a btree node is rewritten.
+ *
+ * BTREE NODES:
+ *
+ * Our unit of allocation is a bucket, and we we can't arbitrarily allocate and
+ * free smaller than a bucket - so, that's how big our btree nodes are.
+ *
+ * (If buckets are really big we'll only use part of the bucket for a btree node
+ * - no less than 1/4th - but a bucket still contains no more than a single
+ * btree node. I'd actually like to change this, but for now we rely on the
+ * bucket's gen for deleting btree nodes when we rewrite/split a node.)
+ *
+ * Anyways, btree nodes are big - big enough to be inefficient with a textbook
+ * btree implementation.
+ *
+ * The way this is solved is that btree nodes are internally log structured; we
+ * can append new keys to an existing btree node without rewriting it. This
+ * means each set of keys we write is sorted, but the node is not.
+ *
+ * We maintain this log structure in memory - keeping 1Mb of keys sorted would
+ * be expensive, and we have to distinguish between the keys we have written and
+ * the keys we haven't. So to do a lookup in a btree node, we have to search
+ * each sorted set. But we do merge written sets together lazily, so the cost of
+ * these extra searches is quite low (normally most of the keys in a btree node
+ * will be in one big set, and then there'll be one or two sets that are much
+ * smaller).
+ *
+ * This log structure makes bcache's btree more of a hybrid between a
+ * conventional btree and a compacting data structure, with some of the
+ * advantages of both.
+ *
+ * GARBAGE COLLECTION:
+ *
+ * We can't just invalidate any bucket - it might contain dirty data or
+ * metadata. If it once contained dirty data, other writes might overwrite it
+ * later, leaving no valid pointers into that bucket in the index.
+ *
+ * Thus, the primary purpose of garbage collection is to find buckets to reuse.
+ * It also counts how much valid data it each bucket currently contains, so that
+ * allocation can reuse buckets sooner when they've been mostly overwritten.
+ *
+ * It also does some things that are really internal to the btree
+ * implementation. If a btree node contains pointers that are stale by more than
+ * some threshold, it rewrites the btree node to avoid the bucket's generation
+ * wrapping around. It also merges adjacent btree nodes if they're empty enough.
+ *
+ * THE JOURNAL:
+ *
+ * Bcache's journal is not necessary for consistency; we always strictly
+ * order metadata writes so that the btree and everything else is consistent on
+ * disk in the event of an unclean shutdown, and in fact bcache had writeback
+ * caching (with recovery from unclean shutdown) before journalling was
+ * implemented.
+ *
+ * Rather, the journal is purely a performance optimization; we can't complete a
+ * write until we've updated the index on disk, otherwise the cache would be
+ * inconsistent in the event of an unclean shutdown. This means that without the
+ * journal, on random write workloads we constantly have to update all the leaf
+ * nodes in the btree, and those writes will be mostly empty (appending at most
+ * a few keys each) - highly inefficient in terms of amount of metadata writes,
+ * and it puts more strain on the various btree resorting/compacting code.
+ *
+ * The journal is just a log of keys we've inserted; on startup we just reinsert
+ * all the keys in the open journal entries. That means that when we're updating
+ * a node in the btree, we can wait until a 4k block of keys fills up before
+ * writing them out.
+ *
+ * For simplicity, we only journal updates to leaf nodes; updates to parent
+ * nodes are rare enough (since our leaf nodes are huge) that it wasn't worth
+ * the complexity to deal with journalling them (in particular, journal replay)
+ * - updates to non leaf nodes just happen synchronously (see btree_split()).
+ */
+
+#define pr_fmt(fmt) "bcache: %s() " fmt "\n", __func__
+
+#include <linux/bio.h>
+#include <linux/blktrace_api.h>
+#include <linux/kobject.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/rbtree.h>
+#include <linux/rwsem.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+
+#include "util.h"
+#include "closure.h"
+
+struct bucket {
+        atomic_t        pin;
+        uint16_t        prio;
+        uint8_t         gen;
+        uint8_t         disk_gen;
+        uint8_t         last_gc; /* Most out of date gen in the btree */
+        uint8_t         gc_gen;
+        uint16_t        gc_mark;
+};
+
+/*
+ * I'd use bitfields for these, but I don't trust the compiler not to screw me
+ * as multiple threads touch struct bucket without locking
+ */
+
+BITMASK(GC_MARK,         struct bucket, gc_mark, 0, 2);
+#define GC_MARK_RECLAIMABLE     0
+#define GC_MARK_DIRTY           1
+#define GC_MARK_METADATA        2
+BITMASK(GC_SECTORS_USED, struct bucket, gc_mark, 2, 14);
+
+struct bkey {
+        uint64_t        high;
+        uint64_t        low;
+        uint64_t        ptr[];
+};
+
+/* Enough for a key with 6 pointers */
+#define BKEY_PAD                8
+
+#define BKEY_PADDED(key)                                        \
+        union { struct bkey key; uint64_t key ## _pad[BKEY_PAD]; }
+
+/* Version 1: Backing device
+ * Version 2: Seed pointer into btree node checksum
+ * Version 3: New UUID format
+ */
+#define BCACHE_SB_VERSION       3
+
+#define SB_SECTOR               8
+#define SB_SIZE                 4096
+#define SB_LABEL_SIZE           32
+#define SB_JOURNAL_BUCKETS      256U
+/* SB_JOURNAL_BUCKETS must be divisible by BITS_PER_LONG */
+#define MAX_CACHES_PER_SET      8
+
+#define BDEV_DATA_START         16      /* sectors */
+
+struct cache_sb {
+        uint64_t                csum;
+        uint64_t                offset; /* sector where this sb was written */
+        uint64_t                version;
+#define CACHE_BACKING_DEV       1
+
+        uint8_t                 magic[16];
+
+        uint8_t                 uuid[16];
+        union {
+                uint8_t         set_uuid[16];
+                uint64_t        set_magic;
+        };
+        uint8_t                 label[SB_LABEL_SIZE];
+
+        uint64_t                flags;
+        uint64_t                seq;
+        uint64_t                pad[8];
+
+        uint64_t                nbuckets;       /* device size */
+        uint16_t                block_size;     /* sectors */
+        uint16_t                bucket_size;    /* sectors */
+
+        uint16_t                nr_in_set;
+        uint16_t                nr_this_dev;
+
+        uint32_t                last_mount;     /* time_t */
+
+        uint16_t                first_bucket;
+        union {
+                uint16_t        njournal_buckets;
+                uint16_t        keys;
+        };
+        uint64_t                d[SB_JOURNAL_BUCKETS];  /* journal buckets */
+};
+
+BITMASK(CACHE_SYNC,             struct cache_sb, flags, 0, 1);
+BITMASK(CACHE_DISCARD,          struct cache_sb, flags, 1, 1);
+BITMASK(CACHE_REPLACEMENT,      struct cache_sb, flags, 2, 3);
+#define CACHE_REPLACEMENT_LRU   0U
+#define CACHE_REPLACEMENT_FIFO  1U
+#define CACHE_REPLACEMENT_RANDOM 2U
+
+BITMASK(BDEV_CACHE_MODE,        struct cache_sb, flags, 0, 4);
+#define CACHE_MODE_WRITETHROUGH 0U
+#define CACHE_MODE_WRITEBACK    1U
+#define CACHE_MODE_WRITEAROUND  2U
+#define CACHE_MODE_NONE         3U
+BITMASK(BDEV_STATE,             struct cache_sb, flags, 61, 2);
+#define BDEV_STATE_NONE         0U
+#define BDEV_STATE_CLEAN        1U
+#define BDEV_STATE_DIRTY        2U
+#define BDEV_STATE_STALE        3U
+
+/* Version 1: Seed pointer into btree node checksum
+ */
+#define BCACHE_BSET_VERSION     1
+
+/*
+ * This is the on disk format for btree nodes - a btree node on disk is a list
+ * of these; within each set the keys are sorted
+ */
+struct bset {
+        uint64_t                csum;
+        uint64_t                magic;
+        uint64_t                seq;
+        uint32_t                version;
+        uint32_t                keys;
+
+        union {
+                struct bkey     start[0];
+                uint64_t        d[0];
+        };
+};
+
+/*
+ * On disk format for priorities and gens - see super.c near prio_write() for
+ * more.
+ */
+struct prio_set {
+        uint64_t                csum;
+        uint64_t                magic;
+        uint64_t                seq;
+        uint32_t                version;
+        uint32_t                pad;
+
+        uint64_t                next_bucket;
+
+        struct bucket_disk {
+                uint16_t        prio;
+                uint8_t         gen;
+        } __attribute((packed)) data[];
+};
+
+struct uuid_entry {
+        union {
+                struct {
+                        uint8_t         uuid[16];
+                        uint8_t         label[32];
+                        uint32_t        first_reg;
+                        uint32_t        last_reg;
+                        uint32_t        invalidated;
+
+                        uint32_t        flags;
+                        /* Size of flash only volumes */
+                        uint64_t        sectors;
+                };
+
+                uint8_t pad[128];
+        };
+};
+
+BITMASK(UUID_FLASH_ONLY,        struct uuid_entry, flags, 0, 1);
+
+#include "journal.h"
+#include "stats.h"
+struct search;
+struct btree;
+struct keybuf;
+
+struct keybuf_key {
+        struct rb_node          node;
+        BKEY_PADDED(key);
+        void                    *private;
+};
+
+typedef bool (keybuf_pred_fn)(struct keybuf *, struct bkey *);
+
+struct keybuf {
+        keybuf_pred_fn          *key_predicate;
+
+        struct bkey             last_scanned;
+        spinlock_t              lock;
+
+        /*
+         * Beginning and end of range in rb tree - so that we can skip taking
+         * lock and checking the rb tree when we need to check for overlapping
+         * keys.
+         */
+        struct bkey             start;
+        struct bkey             end;
+
+        struct rb_root          keys;
+
+#define KEYBUF_NR               100
+        DECLARE_ARRAY_ALLOCATOR(struct keybuf_key, freelist, KEYBUF_NR);
+};
+
+struct bio_split_pool {
+        struct bio_set          *bio_split;
+        mempool_t               *bio_split_hook;
+};
+
+struct bio_split_hook {
+        struct closure          cl;
+        struct bio_split_pool   *p;
+        struct bio              *bio;
+        bio_end_io_t            *bi_end_io;
+        void                    *bi_private;
+};
+
+struct bcache_device {
+        struct closure          cl;
+
+        struct kobject          kobj;
+
+        struct cache_set        *c;
+        unsigned                id;
+#define BCACHEDEVNAME_SIZE      12
+        char                    name[BCACHEDEVNAME_SIZE];
+
+        struct gendisk          *disk;
+
+        /* If nonzero, we're closing */
+        atomic_t                closing;
+
+        /* If nonzero, we're detaching/unregistering from cache set */
+        atomic_t                detaching;
+
+        atomic_long_t           sectors_dirty;
+        unsigned long           sectors_dirty_gc;
+        unsigned long           sectors_dirty_last;
+        long                    sectors_dirty_derivative;
+
+        mempool_t               *unaligned_bvec;
+        struct bio_set          *bio_split;
+
+        unsigned                data_csum:1;
+
+        int (*cache_miss)(struct btree *, struct search *,
+                          struct bio *, unsigned);
+        int (*ioctl) (struct bcache_device *, fmode_t, unsigned, unsigned long);
+
+        struct bio_split_pool   bio_split_hook;
+};
+
+struct io {
+        /* Used to track sequential IO so it can be skipped */
+        struct hlist_node       hash;
+        struct list_head        lru;
+
+        unsigned long           jiffies;
+        unsigned                sequential;
+        sector_t                last;
+};
+
+struct cached_dev {
+        struct list_head        list;
+        struct bcache_device    disk;
+        struct block_device     *bdev;
+
+        struct cache_sb         sb;
+        struct bio              sb_bio;
+        struct bio_vec          sb_bv[1];
+        struct closure_with_waitlist sb_write;
+
+        /* Refcount on the cache set. Always nonzero when we're caching. */
+        atomic_t                count;
+        struct work_struct      detach;
+
+        /*
+         * Device might not be running if it's dirty and the cache set hasn't
+         * showed up yet.
+         */
+        atomic_t                running;
+
+        /*
+         * Writes take a shared lock from start to finish; scanning for dirty
+         * data to refill the rb tree requires an exclusive lock.
+         */
+        struct rw_semaphore     writeback_lock;
+
+        /*
+         * Nonzero, and writeback has a refcount (d->count), iff there is dirty
+         * data in the cache. Protected by writeback_lock; must have an
+         * shared lock to set and exclusive lock to clear.
+         */
+        atomic_t                has_dirty;
+
+        struct ratelimit        writeback_rate;
+        struct delayed_work     writeback_rate_update;
+
+        /*
+         * Internal to the writeback code, so read_dirty() can keep track of
+         * where it's at.
+         */
+        sector_t                last_read;
+
+        /* Number of writeback bios in flight */
+        atomic_t                in_flight;
+        struct closure_with_timer writeback;
+        struct closure_waitlist writeback_wait;
+
+        struct keybuf           writeback_keys;
+
+        /* For tracking sequential IO */
+#define RECENT_IO_BITS  7
+#define RECENT_IO       (1 << RECENT_IO_BITS)
+        struct io               io[RECENT_IO];
+        struct hlist_head       io_hash[RECENT_IO + 1];
+        struct list_head        io_lru;
+        spinlock_t              io_lock;
+
+        struct cache_accounting accounting;
+
+        /* The rest of this all shows up in sysfs */
+        unsigned                sequential_cutoff;
+        unsigned                readahead;
+
+        unsigned                sequential_merge:1;
+        unsigned                verify:1;
+
+        unsigned                writeback_metadata:1;
+        unsigned                writeback_running:1;
+        unsigned char           writeback_percent;
+        unsigned                writeback_delay;
+
+        int                     writeback_rate_change;
+        int64_t                 writeback_rate_derivative;
+        uint64_t                writeback_rate_target;
+
+        unsigned                writeback_rate_update_seconds;
+        unsigned                writeback_rate_d_term;
+        unsigned                writeback_rate_p_term_inverse;
+        unsigned                writeback_rate_d_smooth;
+};
+
+enum alloc_watermarks {
+        WATERMARK_PRIO,
+        WATERMARK_METADATA,
+        WATERMARK_MOVINGGC,
+        WATERMARK_NONE,
+        WATERMARK_MAX
+};
+
+struct cache {
+        struct cache_set        *set;
+        struct cache_sb         sb;
+        struct bio              sb_bio;
+        struct bio_vec          sb_bv[1];
+
+        struct kobject          kobj;
+        struct block_device     *bdev;
+
+        unsigned                watermark[WATERMARK_MAX];
+
+        struct closure          alloc;
+        struct workqueue_struct *alloc_workqueue;
+
+        struct closure          prio;
+        struct prio_set         *disk_buckets;
+
+        /*
+         * When allocating new buckets, prio_write() gets first dibs - since we
+         * may not be allocate at all without writing priorities and gens.
+         * prio_buckets[] contains the last buckets we wrote priorities to (so
+         * gc can mark them as metadata), prio_next[] contains the buckets
+         * allocated for the next prio write.
+         */
+        uint64_t                *prio_buckets;
+        uint64_t                *prio_last_buckets;
+
+        /*
+         * free: Buckets that are ready to be used
+         *
+         * free_inc: Incoming buckets - these are buckets that currently have
+         * cached data in them, and we can't reuse them until after we write
+         * their new gen to disk. After prio_write() finishes writing the new
+         * gens/prios, they'll be moved to the free list (and possibly discarded
+         * in the process)
+         *
+         * unused: GC found nothing pointing into these buckets (possibly
+         * because all the data they contained was overwritten), so we only
+         * need to discard them before they can be moved to the free list.
+         */
+        DECLARE_FIFO(long, free);
+        DECLARE_FIFO(long, free_inc);
+        DECLARE_FIFO(long, unused);
+
+        size_t                  fifo_last_bucket;
+
+        /* Allocation stuff: */
+        struct bucket           *buckets;
+
+        DECLARE_HEAP(struct bucket *, heap);
+
+        /*
+         * max(gen - disk_gen) for all buckets. When it gets too big we have to
+         * call prio_write() to keep gens from wrapping.
+         */
+        uint8_t                 need_save_prio;
+        unsigned                gc_move_threshold;
+
+        /*
+         * If nonzero, we know we aren't going to find any buckets to invalidate
+         * until a gc finishes - otherwise we could pointlessly burn a ton of
+         * cpu
+         */
+        unsigned                invalidate_needs_gc:1;
+
+        bool                    discard; /* Get rid of? */
+
+        /*
+         * We preallocate structs for issuing discards to buckets, and keep them
+         * on this list when they're not in use; do_discard() issues discards
+         * whenever there's work to do and is called by free_some_buckets() and
+         * when a discard finishes.
+         */
+        atomic_t                discards_in_flight;
+        struct list_head        discards;
+
+        struct journal_device   journal;
+
+        /* The rest of this all shows up in sysfs */
+#define IO_ERROR_SHIFT          20
+        atomic_t                io_errors;
+        atomic_t                io_count;
+
+        atomic_long_t           meta_sectors_written;
+        atomic_long_t           btree_sectors_written;
+        atomic_long_t           sectors_written;
+
+        struct bio_split_pool   bio_split_hook;
+};
+
+struct gc_stat {
+        size_t                  nodes;
+        size_t                  key_bytes;
+
+        size_t                  nkeys;
+        uint64_t                data;   /* sectors */
+        uint64_t                dirty;  /* sectors */
+        unsigned                in_use; /* percent */
+};
+
+/*
+ * Flag bits, for how the cache set is shutting down, and what phase it's at:
+ *
+ * CACHE_SET_UNREGISTERING means we're not just shutting down, we're detaching
+ * all the backing devices first (their cached data gets invalidated, and they
+ * won't automatically reattach).
+ *
+ * CACHE_SET_STOPPING always gets set first when we're closing down a cache set;
+ * we'll continue to run normally for awhile with CACHE_SET_STOPPING set (i.e.
+ * flushing dirty data).
+ *
+ * CACHE_SET_STOPPING_2 gets set at the last phase, when it's time to shut down the
+ * allocation thread.
+ */
+#define CACHE_SET_UNREGISTERING         0
+#define CACHE_SET_STOPPING              1
+#define CACHE_SET_STOPPING_2            2
+
+struct cache_set {
+        struct closure          cl;
+
+        struct list_head        list;
+        struct kobject          kobj;
+        struct kobject          internal;
+        struct dentry           *debug;
+        struct cache_accounting accounting;
+
+        unsigned long           flags;
+
+        struct cache_sb         sb;
+
+        struct cache            *cache[MAX_CACHES_PER_SET];
+        struct cache            *cache_by_alloc[MAX_CACHES_PER_SET];
+        int                     caches_loaded;
+
+        struct bcache_device    **devices;
+        struct list_head        cached_devs;
+        uint64_t                cached_dev_sectors;
+        struct closure          caching;
+
+        struct closure_with_waitlist sb_write;
+
+        mempool_t               *search;
+        mempool_t               *bio_meta;
+        struct bio_set          *bio_split;
+
+        /* For the btree cache */
+        struct shrinker         shrink;
+
+        /* For the allocator itself */
+        wait_queue_head_t       alloc_wait;
+
+        /* For the btree cache and anything allocation related */
+        struct mutex            bucket_lock;
+
+        /* log2(bucket_size), in sectors */
+        unsigned short          bucket_bits;
+
+        /* log2(block_size), in sectors */
+        unsigned short          block_bits;
+
+        /*
+         * Default number of pages for a new btree node - may be less than a
+         * full bucket
+         */
+        unsigned                btree_pages;
+
+        /*
+         * Lists of struct btrees; lru is the list for structs that have memory
+         * allocated for actual btree node, freed is for structs that do not.
+         *
+         * We never free a struct btree, except on shutdown - we just put it on
+         * the btree_cache_freed list and reuse it later. This simplifies the
+         * code, and it doesn't cost us much memory as the memory usage is
+         * dominated by buffers that hold the actual btree node data and those
+         * can be freed - and the number of struct btrees allocated is
+         * effectively bounded.
+         *
+         * btree_cache_freeable effectively is a small cache - we use it because
+         * high order page allocations can be rather expensive, and it's quite
+         * common to delete and allocate btree nodes in quick succession. It
+         * should never grow past ~2-3 nodes in practice.
+         */
+        struct list_head        btree_cache;
+        struct list_head        btree_cache_freeable;
+        struct list_head        btree_cache_freed;
+
+        /* Number of elements in btree_cache + btree_cache_freeable lists */
+        unsigned                bucket_cache_used;
+
+        /*
+         * If we need to allocate memory for a new btree node and that
+         * allocation fails, we can cannibalize another node in the btree cache
+         * to satisfy the allocation. However, only one thread can be doing this
+         * at a time, for obvious reasons - try_harder and try_wait are
+         * basically a lock for this that we can wait on asynchronously. The
+         * btree_root() macro releases the lock when it returns.
+         */
+        struct closure          *try_harder;
+        struct closure_waitlist try_wait;
+        uint64_t                try_harder_start;
+
+        /*
+         * When we free a btree node, we increment the gen of the bucket the
+         * node is in - but we can't rewrite the prios and gens until we
+         * finished whatever it is we were doing, otherwise after a crash the
+         * btree node would be freed but for say a split, we might not have the
+         * pointers to the new nodes inserted into the btree yet.
+         *
+         * This is a refcount that blocks prio_write() until the new keys are
+         * written.
+         */
+        atomic_t                prio_blocked;
+        struct closure_waitlist bucket_wait;
+
+        /*
+         * For any bio we don't skip we subtract the number of sectors from
+         * rescale; when it hits 0 we rescale all the bucket priorities.
+         */
+        atomic_t                rescale;
+        /*
+         * When we invalidate buckets, we use both the priority and the amount
+         * of good data to determine which buckets to reuse first - to weight
+         * those together consistently we keep track of the smallest nonzero
+         * priority of any bucket.
+         */
+        uint16_t                min_prio;
+
+        /*
+         * max(gen - gc_gen) for all buckets. When it gets too big we have to gc
+         * to keep gens from wrapping around.
+         */
+        uint8_t                 need_gc;
+        struct gc_stat          gc_stats;
+        size_t                  nbuckets;
+
+        struct closure_with_waitlist gc;
+        /* Where in the btree gc currently is */
+        struct bkey             gc_done;
+
+        /*
+         * The allocation code needs gc_mark in struct bucket to be correct, but
+         * it's not while a gc is in progress. Protected by bucket_lock.
+         */
+        int                     gc_mark_valid;
+
+        /* Counts how many sectors bio_insert has added to the cache */
+        atomic_t                sectors_to_gc;
+
+        struct closure          moving_gc;
+        struct closure_waitlist moving_gc_wait;
+        struct keybuf           moving_gc_keys;
+        /* Number of moving GC bios in flight */
+        atomic_t                in_flight;
+
+        struct btree            *root;
+
+#ifdef CONFIG_BCACHE_DEBUG
+        struct btree            *verify_data;
+        struct mutex            verify_lock;
+#endif
+
+        unsigned                nr_uuids;
+        struct uuid_entry       *uuids;
+        BKEY_PADDED(uuid_bucket);
+        struct closure_with_waitlist uuid_write;
+
+        /*
+         * A btree node on disk could have too many bsets for an iterator to fit
+         * on the stack - this is a single element mempool for btree_read_work()
+         */
+        struct mutex            fill_lock;
+        struct btree_iter       *fill_iter;
+
+        /*
+         * btree_sort() is a merge sort and requires temporary space - single
+         * element mempool
+         */
+        struct mutex            sort_lock;
+        struct bset             *sort;
+
+        /* List of buckets we're currently writing data to */
+        struct list_head        data_buckets;
+        spinlock_t              data_bucket_lock;
+
+        struct journal          journal;
+
+#define CONGESTED_MAX           1024
+        unsigned                congested_last_us;
+        atomic_t                congested;
+
+        /* The rest of this all shows up in sysfs */
+        unsigned                congested_read_threshold_us;
+        unsigned                congested_write_threshold_us;
+
+        spinlock_t              sort_time_lock;
+        struct time_stats       sort_time;
+        struct time_stats       btree_gc_time;
+        struct time_stats       btree_split_time;
+        spinlock_t              btree_read_time_lock;
+        struct time_stats       btree_read_time;
+        struct time_stats       try_harder_time;
+
+        atomic_long_t           cache_read_races;
+        atomic_long_t           writeback_keys_done;
+        atomic_long_t           writeback_keys_failed;
+        unsigned                error_limit;
+        unsigned                error_decay;
+        unsigned short          journal_delay_ms;
+        unsigned                verify:1;
+        unsigned                key_merging_disabled:1;
+        unsigned                gc_always_rewrite:1;
+        unsigned                shrinker_disabled:1;
+        unsigned                copy_gc_enabled:1;
+
+#define BUCKET_HASH_BITS        12
+        struct hlist_head       bucket_hash[1 << BUCKET_HASH_BITS];
+};
+
+static inline bool key_merging_disabled(struct cache_set *c)
+{
+#ifdef CONFIG_BCACHE_DEBUG
+        return c->key_merging_disabled;
+#else
+        return 0;
+#endif
+}
+
+struct bbio {
+        unsigned                submit_time_us;
+        union {
+                struct bkey     key;
+                uint64_t        _pad[3];
+                /*
+                 * We only need pad = 3 here because we only ever carry around a
+                 * single pointer - i.e. the pointer we're doing io to/from.
+                 */
+        };
+        struct bio              bio;
+};
+
+static inline unsigned local_clock_us(void)
+{
+        return local_clock() >> 10;
+}
+
+#define MAX_BSETS               4U
+
+#define BTREE_PRIO              USHRT_MAX
+#define INITIAL_PRIO            32768
+
+#define btree_bytes(c)          ((c)->btree_pages * PAGE_SIZE)
+#define btree_blocks(b)                                                 \
+        ((unsigned) (KEY_SIZE(&b->key) >> (b)->c->block_bits))
+
+#define btree_default_blocks(c)                                         \
+        ((unsigned) ((PAGE_SECTORS * (c)->btree_pages) >> (c)->block_bits))
+
+#define bucket_pages(c)         ((c)->sb.bucket_size / PAGE_SECTORS)
+#define bucket_bytes(c)         ((c)->sb.bucket_size << 9)
+#define block_bytes(c)          ((c)->sb.block_size << 9)
+
+#define __set_bytes(i, k)       (sizeof(*(i)) + (k) * sizeof(uint64_t))
+#define set_bytes(i)            __set_bytes(i, i->keys)
+
+#define __set_blocks(i, k, c)   DIV_ROUND_UP(__set_bytes(i, k), block_bytes(c))
+#define set_blocks(i, c)        __set_blocks(i, (i)->keys, c)
+
+#define node(i, j)              ((struct bkey *) ((i)->d + (j)))
+#define end(i)                  node(i, (i)->keys)
+
+#define index(i, b)                                                     \
+        ((size_t) (((void *) i - (void *) (b)->sets[0].data) /          \
+                   block_bytes(b->c)))
+
+#define btree_data_space(b)     (PAGE_SIZE << (b)->page_order)
+
+#define prios_per_bucket(c)                             \
+        ((bucket_bytes(c) - sizeof(struct prio_set)) /  \
+         sizeof(struct bucket_disk))
+#define prio_buckets(c)                                 \
+        DIV_ROUND_UP((size_t) (c)->sb.nbuckets, prios_per_bucket(c))
+
+#define JSET_MAGIC              0x245235c1a3625032ULL
+#define PSET_MAGIC              0x6750e15f87337f91ULL
+#define BSET_MAGIC              0x90135c78b99e07f5ULL
+
+#define jset_magic(c)           ((c)->sb.set_magic ^ JSET_MAGIC)
+#define pset_magic(c)           ((c)->sb.set_magic ^ PSET_MAGIC)
+#define bset_magic(c)           ((c)->sb.set_magic ^ BSET_MAGIC)
+
+/* Bkey fields: all units are in sectors */
+
+#define KEY_FIELD(name, field, offset, size)                            \
+        BITMASK(name, struct bkey, field, offset, size)
+
+#define PTR_FIELD(name, offset, size)                                   \
+        static inline uint64_t name(const struct bkey *k, unsigned i)   \
+        { return (k->ptr[i] >> offset) & ~(((uint64_t) ~0) << size); }  \
+                                                                        \
+        static inline void SET_##name(struct bkey *k, unsigned i, uint64_t v)\
+        {                                                               \
+                k->ptr[i] &= ~(~((uint64_t) ~0 << size) << offset);     \
+                k->ptr[i] |= v << offset;                               \
+        }
+
+KEY_FIELD(KEY_PTRS,     high, 60, 3)
+KEY_FIELD(HEADER_SIZE,  high, 58, 2)
+KEY_FIELD(KEY_CSUM,     high, 56, 2)
+KEY_FIELD(KEY_PINNED,   high, 55, 1)
+KEY_FIELD(KEY_DIRTY,    high, 36, 1)
+
+KEY_FIELD(KEY_SIZE,     high, 20, 16)
+KEY_FIELD(KEY_INODE,    high, 0,  20)
+
+/* Next time I change the on disk format, KEY_OFFSET() won't be 64 bits */
+
+static inline uint64_t KEY_OFFSET(const struct bkey *k)
+{
+        return k->low;
+}
+
+static inline void SET_KEY_OFFSET(struct bkey *k, uint64_t v)
+{
+        k->low = v;
+}
+
+PTR_FIELD(PTR_DEV,              51, 12)
+PTR_FIELD(PTR_OFFSET,           8,  43)
+PTR_FIELD(PTR_GEN,              0,  8)
+
+#define PTR_CHECK_DEV           ((1 << 12) - 1)
+
+#define PTR(gen, offset, dev)                                           \
+        ((((uint64_t) dev) << 51) | ((uint64_t) offset) << 8 | gen)
+
+static inline size_t sector_to_bucket(struct cache_set *c, sector_t s)
+{
+        return s >> c->bucket_bits;
+}
+
+static inline sector_t bucket_to_sector(struct cache_set *c, size_t b)
+{
+        return ((sector_t) b) << c->bucket_bits;
+}
+
+static inline sector_t bucket_remainder(struct cache_set *c, sector_t s)
+{
+        return s & (c->sb.bucket_size - 1);
+}
+
+static inline struct cache *PTR_CACHE(struct cache_set *c,
+                                      const struct bkey *k,
+                                      unsigned ptr)
+{
+        return c->cache[PTR_DEV(k, ptr)];
+}
+
+static inline size_t PTR_BUCKET_NR(struct cache_set *c,
+                                   const struct bkey *k,
+                                   unsigned ptr)
+{
+        return sector_to_bucket(c, PTR_OFFSET(k, ptr));
+}
+
+static inline struct bucket *PTR_BUCKET(struct cache_set *c,
+                                        const struct bkey *k,
+                                        unsigned ptr)
+{
+        return PTR_CACHE(c, k, ptr)->buckets + PTR_BUCKET_NR(c, k, ptr);
+}
+
+/* Btree key macros */
+
+/*
+ * The high bit being set is a relic from when we used it to do binary
+ * searches - it told you where a key started. It's not used anymore,
+ * and can probably be safely dropped.
+ */
+#define KEY(dev, sector, len)   (struct bkey)                           \
+{                                                                       \
+        .high = (1ULL << 63) | ((uint64_t) (len) << 20) | (dev),        \
+        .low = (sector)                                                 \
+}
+
+static inline void bkey_init(struct bkey *k)
+{
+        *k = KEY(0, 0, 0);
+}
+
+#define KEY_START(k)            (KEY_OFFSET(k) - KEY_SIZE(k))
+#define START_KEY(k)            KEY(KEY_INODE(k), KEY_START(k), 0)
+#define MAX_KEY                 KEY(~(~0 << 20), ((uint64_t) ~0) >> 1, 0)
+#define ZERO_KEY                KEY(0, 0, 0)
+
+/*
+ * This is used for various on disk data structures - cache_sb, prio_set, bset,
+ * jset: The checksum is _always_ the first 8 bytes of these structs
+ */
+#define csum_set(i)                                                     \
+        crc64(((void *) (i)) + sizeof(uint64_t),                        \
+              ((void *) end(i)) - (((void *) (i)) + sizeof(uint64_t)))
+
+/* Error handling macros */
+
+#define btree_bug(b, ...)                                               \
+do {                                                                    \
+        if (bch_cache_set_error((b)->c, __VA_ARGS__))                   \
+                dump_stack();                                           \
+} while (0)
+
+#define cache_bug(c, ...)                                               \
+do {                                                                    \
+        if (bch_cache_set_error(c, __VA_ARGS__))                        \
+                dump_stack();                                           \
+} while (0)
+
+#define btree_bug_on(cond, b, ...)                                      \
+do {                                                                    \
+        if (cond)                                                       \
+                btree_bug(b, __VA_ARGS__);                              \
+} while (0)
+
+#define cache_bug_on(cond, c, ...)                                      \
+do {                                                                    \
+        if (cond)                                                       \
+                cache_bug(c, __VA_ARGS__);                              \
+} while (0)
+
+#define cache_set_err_on(cond, c, ...)                                  \
+do {                                                                    \
+        if (cond)                                                       \
+                bch_cache_set_error(c, __VA_ARGS__);                    \
+} while (0)
+
+/* Looping macros */
+
+#define for_each_cache(ca, cs, iter)                                    \
+        for (iter = 0; ca = cs->cache[iter], iter < (cs)->sb.nr_in_set; iter++)
+
+#define for_each_bucket(b, ca)                                          \
+        for (b = (ca)->buckets + (ca)->sb.first_bucket;                 \
+             b < (ca)->buckets + (ca)->sb.nbuckets; b++)
+
+static inline void __bkey_put(struct cache_set *c, struct bkey *k)
+{
+        unsigned i;
+
+        for (i = 0; i < KEY_PTRS(k); i++)
+                atomic_dec_bug(&PTR_BUCKET(c, k, i)->pin);
+}
+
+/* Blktrace macros */
+
+#define blktrace_msg(c, fmt, ...)                                       \
+do {                                                                    \
+        struct request_queue *q = bdev_get_queue(c->bdev);              \
+        if (q)                                                          \
+                blk_add_trace_msg(q, fmt, ##__VA_ARGS__);               \
+} while (0)
+
+#define blktrace_msg_all(s, fmt, ...)                                   \
+do {                                                                    \
+        struct cache *_c;                                               \
+        unsigned i;                                                     \
+        for_each_cache(_c, (s), i)                                      \
+                blktrace_msg(_c, fmt, ##__VA_ARGS__);                   \
+} while (0)
+
+static inline void cached_dev_put(struct cached_dev *dc)
+{
+        if (atomic_dec_and_test(&dc->count))
+                schedule_work(&dc->detach);
+}
+
+static inline bool cached_dev_get(struct cached_dev *dc)
+{
+        if (!atomic_inc_not_zero(&dc->count))
+                return false;
+
+        /* Paired with the mb in cached_dev_attach */
+        smp_mb__after_atomic_inc();
+        return true;
+}
+
+/*
+ * bucket_gc_gen() returns the difference between the bucket's current gen and
+ * the oldest gen of any pointer into that bucket in the btree (last_gc).
+ *
+ * bucket_disk_gen() returns the difference between the current gen and the gen
+ * on disk; they're both used to make sure gens don't wrap around.
+ */
+
+static inline uint8_t bucket_gc_gen(struct bucket *b)
+{
+        return b->gen - b->last_gc;
+}
+
+static inline uint8_t bucket_disk_gen(struct bucket *b)
+{
+        return b->gen - b->disk_gen;
+}
+
+#define BUCKET_GC_GEN_MAX       96U
+#define BUCKET_DISK_GEN_MAX     64U
+
+#define kobj_attribute_write(n, fn)                                     \
+        static struct kobj_attribute ksysfs_##n = __ATTR(n, S_IWUSR, NULL, fn)
+
+#define kobj_attribute_rw(n, show, store)                               \
+        static struct kobj_attribute ksysfs_##n =                       \
+                __ATTR(n, S_IWUSR|S_IRUSR, show, store)
+
+/* Forward declarations */
+
+void bch_writeback_queue(struct cached_dev *);
+void bch_writeback_add(struct cached_dev *, unsigned);
+
+void bch_count_io_errors(struct cache *, int, const char *);
+void bch_bbio_count_io_errors(struct cache_set *, struct bio *,
+                              int, const char *);
+void bch_bbio_endio(struct cache_set *, struct bio *, int, const char *);
+void bch_bbio_free(struct bio *, struct cache_set *);
+struct bio *bch_bbio_alloc(struct cache_set *);
+
+struct bio *bch_bio_split(struct bio *, int, gfp_t, struct bio_set *);
+void bch_generic_make_request(struct bio *, struct bio_split_pool *);
+void __bch_submit_bbio(struct bio *, struct cache_set *);
+void bch_submit_bbio(struct bio *, struct cache_set *, struct bkey *, unsigned);
+
+uint8_t bch_inc_gen(struct cache *, struct bucket *);
+void bch_rescale_priorities(struct cache_set *, int);
+bool bch_bucket_add_unused(struct cache *, struct bucket *);
+void bch_allocator_thread(struct closure *);
+
+long bch_bucket_alloc(struct cache *, unsigned, struct closure *);
+void bch_bucket_free(struct cache_set *, struct bkey *);
+
+int __bch_bucket_alloc_set(struct cache_set *, unsigned,
+                           struct bkey *, int, struct closure *);
+int bch_bucket_alloc_set(struct cache_set *, unsigned,
+                         struct bkey *, int, struct closure *);
+
+__printf(2, 3)
+bool bch_cache_set_error(struct cache_set *, const char *, ...);
+
+void bch_prio_write(struct cache *);
+void bch_write_bdev_super(struct cached_dev *, struct closure *);
+
+extern struct workqueue_struct *bcache_wq, *bch_gc_wq;
+extern const char * const bch_cache_modes[];
+extern struct mutex bch_register_lock;
+extern struct list_head bch_cache_sets;
+
+extern struct kobj_type bch_cached_dev_ktype;
+extern struct kobj_type bch_flash_dev_ktype;
+extern struct kobj_type bch_cache_set_ktype;
+extern struct kobj_type bch_cache_set_internal_ktype;
+extern struct kobj_type bch_cache_ktype;
+
+void bch_cached_dev_release(struct kobject *);
+void bch_flash_dev_release(struct kobject *);
+void bch_cache_set_release(struct kobject *);
+void bch_cache_release(struct kobject *);
+
+int bch_uuid_write(struct cache_set *);
+void bcache_write_super(struct cache_set *);
+
+int bch_flash_dev_create(struct cache_set *c, uint64_t size);
+
+int bch_cached_dev_attach(struct cached_dev *, struct cache_set *);
+void bch_cached_dev_detach(struct cached_dev *);
+void bch_cached_dev_run(struct cached_dev *);
+void bcache_device_stop(struct bcache_device *);
+
+void bch_cache_set_unregister(struct cache_set *);
+void bch_cache_set_stop(struct cache_set *);
+
+struct cache_set *bch_cache_set_alloc(struct cache_sb *);
+void bch_btree_cache_free(struct cache_set *);
+int bch_btree_cache_alloc(struct cache_set *);
+void bch_writeback_init_cached_dev(struct cached_dev *);
+void bch_moving_init_cache_set(struct cache_set *);
+
+void bch_cache_allocator_exit(struct cache *ca);
+int bch_cache_allocator_init(struct cache *ca);
+
+void bch_debug_exit(void);
+int bch_debug_init(struct kobject *);
+void bch_writeback_exit(void);
+int bch_writeback_init(void);
+void bch_request_exit(void);
+int bch_request_init(void);
+void bch_btree_exit(void);
+int bch_btree_init(void);
+
+#endif /* _BCACHE_H */
diff --git a/drivers/md/bcache/bset.c b/drivers/md/bcache/bset.c
new file mode 100644
index 000000000000..bb0f7ae14b3c
--- /dev/null
+++ b/drivers/md/bcache/bset.c
@@ -0,0 +1,1190 @@
+/*
+ * Code for working with individual keys, and sorted sets of keys with in a
+ * btree node
+ *
+ * Copyright 2012 Google, Inc.
+ */
+
+#include "bcache.h"
+#include "btree.h"
+#include "debug.h"
+
+#include <linux/random.h>
+
+/* Keylists */
+
+void bch_keylist_copy(struct keylist *dest, struct keylist *src)
+{
+        *dest = *src;
+
+        if (src->list == src->d) {
+                size_t n = (uint64_t *) src->top - src->d;
+                dest->top = (struct bkey *) &dest->d[n];
+                dest->list = dest->d;
+        }
+}
+
+int bch_keylist_realloc(struct keylist *l, int nptrs, struct cache_set *c)
+{
+        unsigned oldsize = (uint64_t *) l->top - l->list;
+        unsigned newsize = oldsize + 2 + nptrs;
+        uint64_t *new;
+
+        /* The journalling code doesn't handle the case where the keys to insert
+         * is bigger than an empty write: If we just return -ENOMEM here,
+         * bio_insert() and bio_invalidate() will insert the keys created so far
+         * and finish the rest when the keylist is empty.
+         */
+        if (newsize * sizeof(uint64_t) > block_bytes(c) - sizeof(struct jset))
+                return -ENOMEM;
+
+        newsize = roundup_pow_of_two(newsize);
+
+        if (newsize <= KEYLIST_INLINE ||
+            roundup_pow_of_two(oldsize) == newsize)
+                return 0;
+
+        new = krealloc(l->list == l->d ? NULL : l->list,
+                       sizeof(uint64_t) * newsize, GFP_NOIO);
+
+        if (!new)
+                return -ENOMEM;
+
+        if (l->list == l->d)
+                memcpy(new, l->list, sizeof(uint64_t) * KEYLIST_INLINE);
+
+        l->list = new;
+        l->top = (struct bkey *) (&l->list[oldsize]);
+
+        return 0;
+}
+
+struct bkey *bch_keylist_pop(struct keylist *l)
+{
+        struct bkey *k = l->bottom;
+
+        if (k == l->top)
+                return NULL;
+
+        while (bkey_next(k) != l->top)
+                k = bkey_next(k);
+
+        return l->top = k;
+}
+
+/* Pointer validation */
+
+bool __bch_ptr_invalid(struct cache_set *c, int level, const struct bkey *k)
+{
+        unsigned i;
+
+        if (level && (!KEY_PTRS(k) || !KEY_SIZE(k) || KEY_DIRTY(k)))
+                goto bad;
+
+        if (!level && KEY_SIZE(k) > KEY_OFFSET(k))
+                goto bad;
+
+        if (!KEY_SIZE(k))
+                return true;
+
+        for (i = 0; i < KEY_PTRS(k); i++)
+                if (ptr_available(c, k, i)) {
+                        struct cache *ca = PTR_CACHE(c, k, i);
+                        size_t bucket = PTR_BUCKET_NR(c, k, i);
+                        size_t r = bucket_remainder(c, PTR_OFFSET(k, i));
+
+                        if (KEY_SIZE(k) + r > c->sb.bucket_size ||
+                            bucket <  ca->sb.first_bucket ||
+                            bucket >= ca->sb.nbuckets)
+                                goto bad;
+                }
+
+        return false;
+bad:
+        cache_bug(c, "spotted bad key %s: %s", pkey(k), bch_ptr_status(c, k));
+        return true;
+}
+
+bool bch_ptr_bad(struct btree *b, const struct bkey *k)
+{
+        struct bucket *g;
+        unsigned i, stale;
+
+        if (!bkey_cmp(k, &ZERO_KEY) ||
+            !KEY_PTRS(k) ||
+            bch_ptr_invalid(b, k))
+                return true;
+
+        if (KEY_PTRS(k) && PTR_DEV(k, 0) == PTR_CHECK_DEV)
+                return true;
+
+        for (i = 0; i < KEY_PTRS(k); i++)
+                if (ptr_available(b->c, k, i)) {
+                        g = PTR_BUCKET(b->c, k, i);
+                        stale = ptr_stale(b->c, k, i);
+
+                        btree_bug_on(stale > 96, b,
+                                     "key too stale: %i, need_gc %u",
+                                     stale, b->c->need_gc);
+
+                        btree_bug_on(stale && KEY_DIRTY(k) && KEY_SIZE(k),
+                                     b, "stale dirty pointer");
+
+                        if (stale)
+                                return true;
+
+#ifdef CONFIG_BCACHE_EDEBUG
+                        if (!mutex_trylock(&b->c->bucket_lock))
+                                continue;
+
+                        if (b->level) {
+                                if (KEY_DIRTY(k) ||
+                                    g->prio != BTREE_PRIO ||
+                                    (b->c->gc_mark_valid &&
+                                     GC_MARK(g) != GC_MARK_METADATA))
+                                        goto bug;
+
+                        } else {
+                                if (g->prio == BTREE_PRIO)
+                                        goto bug;
+
+                                if (KEY_DIRTY(k) &&
+                                    b->c->gc_mark_valid &&
+                                    GC_MARK(g) != GC_MARK_DIRTY)
+                                        goto bug;
+                        }
+                        mutex_unlock(&b->c->bucket_lock);
+#endif
+                }
+
+        return false;
+#ifdef CONFIG_BCACHE_EDEBUG
+bug:
+        mutex_unlock(&b->c->bucket_lock);
+        btree_bug(b, "inconsistent pointer %s: bucket %li pin %i "
+                  "prio %i gen %i last_gc %i mark %llu gc_gen %i", pkey(k),
+                  PTR_BUCKET_NR(b->c, k, i), atomic_read(&g->pin),
+                  g->prio, g->gen, g->last_gc, GC_MARK(g), g->gc_gen);
+        return true;
+#endif
+}
+
+/* Key/pointer manipulation */
+
+void bch_bkey_copy_single_ptr(struct bkey *dest, const struct bkey *src,
+                              unsigned i)
+{
+        BUG_ON(i > KEY_PTRS(src));
+
+        /* Only copy the header, key, and one pointer. */
+        memcpy(dest, src, 2 * sizeof(uint64_t));
+        dest->ptr[0] = src->ptr[i];
+        SET_KEY_PTRS(dest, 1);
+        /* We didn't copy the checksum so clear that bit. */
+        SET_KEY_CSUM(dest, 0);
+}
+
+bool __bch_cut_front(const struct bkey *where, struct bkey *k)
+{
+        unsigned i, len = 0;
+
+        if (bkey_cmp(where, &START_KEY(k)) <= 0)
+                return false;
+
+        if (bkey_cmp(where, k) < 0)
+                len = KEY_OFFSET(k) - KEY_OFFSET(where);
+        else
+                bkey_copy_key(k, where);
+
+        for (i = 0; i < KEY_PTRS(k); i++)
+                SET_PTR_OFFSET(k, i, PTR_OFFSET(k, i) + KEY_SIZE(k) - len);
+
+        BUG_ON(len > KEY_SIZE(k));
+        SET_KEY_SIZE(k, len);
+        return true;
+}
+
+bool __bch_cut_back(const struct bkey *where, struct bkey *k)
+{
+        unsigned len = 0;
+
+        if (bkey_cmp(where, k) >= 0)
+                return false;
+
+        BUG_ON(KEY_INODE(where) != KEY_INODE(k));
+
+        if (bkey_cmp(where, &START_KEY(k)) > 0)
+                len = KEY_OFFSET(where) - KEY_START(k);
+
+        bkey_copy_key(k, where);
+
+        BUG_ON(len > KEY_SIZE(k));
+        SET_KEY_SIZE(k, len);
+        return true;
+}
+
+static uint64_t merge_chksums(struct bkey *l, struct bkey *r)
+{
+        return (l->ptr[KEY_PTRS(l)] + r->ptr[KEY_PTRS(r)]) &
+                ~((uint64_t)1 << 63);
+}
+
+/* Tries to merge l and r: l should be lower than r
+ * Returns true if we were able to merge. If we did merge, l will be the merged
+ * key, r will be untouched.
+ */
+bool bch_bkey_try_merge(struct btree *b, struct bkey *l, struct bkey *r)
+{
+        unsigned i;
+
+        if (key_merging_disabled(b->c))
+                return false;
+
+        if (KEY_PTRS(l) != KEY_PTRS(r) ||
+            KEY_DIRTY(l) != KEY_DIRTY(r) ||
+            bkey_cmp(l, &START_KEY(r)))
+                return false;
+
+        for (i = 0; i < KEY_PTRS(l); i++)
+                if (l->ptr[i] + PTR(0, KEY_SIZE(l), 0) != r->ptr[i] ||
+                    PTR_BUCKET_NR(b->c, l, i) != PTR_BUCKET_NR(b->c, r, i))
+                        return false;
+
+        /* Keys with no pointers aren't restricted to one bucket and could
+         * overflow KEY_SIZE
+         */
+        if (KEY_SIZE(l) + KEY_SIZE(r) > USHRT_MAX) {
+                SET_KEY_OFFSET(l, KEY_OFFSET(l) + USHRT_MAX - KEY_SIZE(l));
+                SET_KEY_SIZE(l, USHRT_MAX);
+
+                bch_cut_front(l, r);
+                return false;
+        }
+
+        if (KEY_CSUM(l)) {
+                if (KEY_CSUM(r))
+                        l->ptr[KEY_PTRS(l)] = merge_chksums(l, r);
+                else
+                        SET_KEY_CSUM(l, 0);
+        }
+
+        SET_KEY_OFFSET(l, KEY_OFFSET(l) + KEY_SIZE(r));
+        SET_KEY_SIZE(l, KEY_SIZE(l) + KEY_SIZE(r));
+
+        return true;
+}
+
+/* Binary tree stuff for auxiliary search trees */
+
+static unsigned inorder_next(unsigned j, unsigned size)
+{
+        if (j * 2 + 1 < size) {
+                j = j * 2 + 1;
+
+                while (j * 2 < size)
+                        j *= 2;
+        } else
+                j >>= ffz(j) + 1;
+
+        return j;
+}
+
+static unsigned inorder_prev(unsigned j, unsigned size)
+{
+        if (j * 2 < size) {
+                j = j * 2;
+
+                while (j * 2 + 1 < size)
+                        j = j * 2 + 1;
+        } else
+                j >>= ffs(j);
+
+        return j;
+}
+
+/* I have no idea why this code works... and I'm the one who wrote it
+ *
+ * However, I do know what it does:
+ * Given a binary tree constructed in an array (i.e. how you normally implement
+ * a heap), it converts a node in the tree - referenced by array index - to the
+ * index it would have if you did an inorder traversal.
+ *
+ * Also tested for every j, size up to size somewhere around 6 million.
+ *
+ * The binary tree starts at array index 1, not 0
+ * extra is a function of size:
+ *   extra = (size - rounddown_pow_of_two(size - 1)) << 1;
+ */
+static unsigned __to_inorder(unsigned j, unsigned size, unsigned extra)
+{
+        unsigned b = fls(j);
+        unsigned shift = fls(size - 1) - b;
+
+        j  ^= 1U << (b - 1);
+        j <<= 1;
+        j  |= 1;
+        j <<= shift;
+
+        if (j > extra)
+                j -= (j - extra) >> 1;
+
+        return j;
+}
+
+static unsigned to_inorder(unsigned j, struct bset_tree *t)
+{
+        return __to_inorder(j, t->size, t->extra);
+}
+
+static unsigned __inorder_to_tree(unsigned j, unsigned size, unsigned extra)
+{
+        unsigned shift;
+
+        if (j > extra)
+                j += j - extra;
+
+        shift = ffs(j);
+
+        j >>= shift;
+        j  |= roundup_pow_of_two(size) >> shift;
+
+        return j;
+}
+
+static unsigned inorder_to_tree(unsigned j, struct bset_tree *t)
+{
+        return __inorder_to_tree(j, t->size, t->extra);
+}
+
+#if 0
+void inorder_test(void)
+{
+        unsigned long done = 0;
+        ktime_t start = ktime_get();
+
+        for (unsigned size = 2;
+             size < 65536000;
+             size++) {
+                unsigned extra = (size - rounddown_pow_of_two(size - 1)) << 1;
+                unsigned i = 1, j = rounddown_pow_of_two(size - 1);
+
+                if (!(size % 4096))
+                        printk(KERN_NOTICE "loop %u, %llu per us\n", size,
+                               done / ktime_us_delta(ktime_get(), start));
+
+                while (1) {
+                        if (__inorder_to_tree(i, size, extra) != j)
+                                panic("size %10u j %10u i %10u", size, j, i);
+
+                        if (__to_inorder(j, size, extra) != i)
+                                panic("size %10u j %10u i %10u", size, j, i);
+
+                        if (j == rounddown_pow_of_two(size) - 1)
+                                break;
+
+                        BUG_ON(inorder_prev(inorder_next(j, size), size) != j);
+
+                        j = inorder_next(j, size);
+                        i++;
+                }
+
+                done += size - 1;
+        }
+}
+#endif
+
+/*
+ * Cacheline/offset <-> bkey pointer arithmatic:
+ *
+ * t->tree is a binary search tree in an array; each node corresponds to a key
+ * in one cacheline in t->set (BSET_CACHELINE bytes).
+ *
+ * This means we don't have to store the full index of the key that a node in
+ * the binary tree points to; to_inorder() gives us the cacheline, and then
+ * bkey_float->m gives us the offset within that cacheline, in units of 8 bytes.
+ *
+ * cacheline_to_bkey() and friends abstract out all the pointer arithmatic to
+ * make this work.
+ *
+ * To construct the bfloat for an arbitrary key we need to know what the key
+ * immediately preceding it is: we have to check if the two keys differ in the
+ * bits we're going to store in bkey_float->mantissa. t->prev[j] stores the size
+ * of the previous key so we can walk backwards to it from t->tree[j]'s key.
+ */
+
+static struct bkey *cacheline_to_bkey(struct bset_tree *t, unsigned cacheline,
+                                      unsigned offset)
+{
+        return ((void *) t->data) + cacheline * BSET_CACHELINE + offset * 8;
+}
+
+static unsigned bkey_to_cacheline(struct bset_tree *t, struct bkey *k)
+{
+        return ((void *) k - (void *) t->data) / BSET_CACHELINE;
+}
+
+static unsigned bkey_to_cacheline_offset(struct bkey *k)
+{
+        return ((size_t) k & (BSET_CACHELINE - 1)) / sizeof(uint64_t);
+}
+
+static struct bkey *tree_to_bkey(struct bset_tree *t, unsigned j)
+{
+        return cacheline_to_bkey(t, to_inorder(j, t), t->tree[j].m);
+}
+
+static struct bkey *tree_to_prev_bkey(struct bset_tree *t, unsigned j)
+{
+        return (void *) (((uint64_t *) tree_to_bkey(t, j)) - t->prev[j]);
+}
+
+/*
+ * For the write set - the one we're currently inserting keys into - we don't
+ * maintain a full search tree, we just keep a simple lookup table in t->prev.
+ */
+static struct bkey *table_to_bkey(struct bset_tree *t, unsigned cacheline)
+{
+        return cacheline_to_bkey(t, cacheline, t->prev[cacheline]);
+}
+
+static inline uint64_t shrd128(uint64_t high, uint64_t low, uint8_t shift)
+{
+#ifdef CONFIG_X86_64
+        asm("shrd %[shift],%[high],%[low]"
+            : [low] "+Rm" (low)
+            : [high] "R" (high),
+            [shift] "ci" (shift)
+            : "cc");
+#else
+        low >>= shift;
+        low  |= (high << 1) << (63U - shift);
+#endif
+        return low;
+}
+
+static inline unsigned bfloat_mantissa(const struct bkey *k,
+                                       struct bkey_float *f)
+{
+        const uint64_t *p = &k->low - (f->exponent >> 6);
+        return shrd128(p[-1], p[0], f->exponent & 63) & BKEY_MANTISSA_MASK;
+}
+
+static void make_bfloat(struct bset_tree *t, unsigned j)
+{
+        struct bkey_float *f = &t->tree[j];
+        struct bkey *m = tree_to_bkey(t, j);
+        struct bkey *p = tree_to_prev_bkey(t, j);
+
+        struct bkey *l = is_power_of_2(j)
+                ? t->data->start
+                : tree_to_prev_bkey(t, j >> ffs(j));
+
+        struct bkey *r = is_power_of_2(j + 1)
+                ? node(t->data, t->data->keys - bkey_u64s(&t->end))
+                : tree_to_bkey(t, j >> (ffz(j) + 1));
+
+        BUG_ON(m < l || m > r);
+        BUG_ON(bkey_next(p) != m);
+
+        if (KEY_INODE(l) != KEY_INODE(r))
+                f->exponent = fls64(KEY_INODE(r) ^ KEY_INODE(l)) + 64;
+        else
+                f->exponent = fls64(r->low ^ l->low);
+
+        f->exponent = max_t(int, f->exponent - BKEY_MANTISSA_BITS, 0);
+
+        /*
+         * Setting f->exponent = 127 flags this node as failed, and causes the
+         * lookup code to fall back to comparing against the original key.
+         */
+
+        if (bfloat_mantissa(m, f) != bfloat_mantissa(p, f))
+                f->mantissa = bfloat_mantissa(m, f) - 1;
+        else
+                f->exponent = 127;
+}
+
+static void bset_alloc_tree(struct btree *b, struct bset_tree *t)
+{
+        if (t != b->sets) {
+                unsigned j = roundup(t[-1].size,
+                                     64 / sizeof(struct bkey_float));
+
+                t->tree = t[-1].tree + j;
+                t->prev = t[-1].prev + j;
+        }
+
+        while (t < b->sets + MAX_BSETS)
+                t++->size = 0;
+}
+
+static void bset_build_unwritten_tree(struct btree *b)
+{
+        struct bset_tree *t = b->sets + b->nsets;
+
+        bset_alloc_tree(b, t);
+
+        if (t->tree != b->sets->tree + bset_tree_space(b)) {
+                t->prev[0] = bkey_to_cacheline_offset(t->data->start);
+                t->size = 1;
+        }
+}
+
+static void bset_build_written_tree(struct btree *b)
+{
+        struct bset_tree *t = b->sets + b->nsets;
+        struct bkey *k = t->data->start;
+        unsigned j, cacheline = 1;
+
+        bset_alloc_tree(b, t);
+
+        t->size = min_t(unsigned,
+                        bkey_to_cacheline(t, end(t->data)),
+                        b->sets->tree + bset_tree_space(b) - t->tree);
+
+        if (t->size < 2) {
+                t->size = 0;
+                return;
+        }
+
+        t->extra = (t->size - rounddown_pow_of_two(t->size - 1)) << 1;
+
+        /* First we figure out where the first key in each cacheline is */
+        for (j = inorder_next(0, t->size);
+             j;
+             j = inorder_next(j, t->size)) {
+                while (bkey_to_cacheline(t, k) != cacheline)
+                        k = bkey_next(k);
+
+                t->prev[j] = bkey_u64s(k);
+                k = bkey_next(k);
+                cacheline++;
+                t->tree[j].m = bkey_to_cacheline_offset(k);
+        }
+
+        while (bkey_next(k) != end(t->data))
+                k = bkey_next(k);
+
+        t->end = *k;
+
+        /* Then we build the tree */
+        for (j = inorder_next(0, t->size);
+             j;
+             j = inorder_next(j, t->size))
+                make_bfloat(t, j);
+}
+
+void bch_bset_fix_invalidated_key(struct btree *b, struct bkey *k)
+{
+        struct bset_tree *t;
+        unsigned inorder, j = 1;
+
+        for (t = b->sets; t <= &b->sets[b->nsets]; t++)
+                if (k < end(t->data))
+                        goto found_set;
+
+        BUG();
+found_set:
+        if (!t->size || !bset_written(b, t))
+                return;
+
+        inorder = bkey_to_cacheline(t, k);
+
+        if (k == t->data->start)
+                goto fix_left;
+
+        if (bkey_next(k) == end(t->data)) {
+                t->end = *k;
+                goto fix_right;
+        }
+
+        j = inorder_to_tree(inorder, t);
+
+        if (j &&
+            j < t->size &&
+            k == tree_to_bkey(t, j))
+fix_left:       do {
+                        make_bfloat(t, j);
+                        j = j * 2;
+                } while (j < t->size);
+
+        j = inorder_to_tree(inorder + 1, t);
+
+        if (j &&
+            j < t->size &&
+            k == tree_to_prev_bkey(t, j))
+fix_right:      do {
+                        make_bfloat(t, j);
+                        j = j * 2 + 1;
+                } while (j < t->size);
+}
+
+void bch_bset_fix_lookup_table(struct btree *b, struct bkey *k)
+{
+        struct bset_tree *t = &b->sets[b->nsets];
+        unsigned shift = bkey_u64s(k);
+        unsigned j = bkey_to_cacheline(t, k);
+
+        /* We're getting called from btree_split() or btree_gc, just bail out */
+        if (!t->size)
+                return;
+
+        /* k is the key we just inserted; we need to find the entry in the
+         * lookup table for the first key that is strictly greater than k:
+         * it's either k's cacheline or the next one
+         */
+        if (j < t->size &&
+            table_to_bkey(t, j) <= k)
+                j++;
+
+        /* Adjust all the lookup table entries, and find a new key for any that
+         * have gotten too big
+         */
+        for (; j < t->size; j++) {
+                t->prev[j] += shift;
+
+                if (t->prev[j] > 7) {
+                        k = table_to_bkey(t, j - 1);
+
+                        while (k < cacheline_to_bkey(t, j, 0))
+                                k = bkey_next(k);
+
+                        t->prev[j] = bkey_to_cacheline_offset(k);
+                }
+        }
+
+        if (t->size == b->sets->tree + bset_tree_space(b) - t->tree)
+                return;
+
+        /* Possibly add a new entry to the end of the lookup table */
+
+        for (k = table_to_bkey(t, t->size - 1);
+             k != end(t->data);
+             k = bkey_next(k))
+                if (t->size == bkey_to_cacheline(t, k)) {
+                        t->prev[t->size] = bkey_to_cacheline_offset(k);
+                        t->size++;
+                }
+}
+
+void bch_bset_init_next(struct btree *b)
+{
+        struct bset *i = write_block(b);
+
+        if (i != b->sets[0].data) {
+                b->sets[++b->nsets].data = i;
+                i->seq = b->sets[0].data->seq;
+        } else
+                get_random_bytes(&i->seq, sizeof(uint64_t));
+
+        i->magic        = bset_magic(b->c);
+        i->version      = 0;
+        i->keys         = 0;
+
+        bset_build_unwritten_tree(b);
+}
+
+struct bset_search_iter {
+        struct bkey *l, *r;
+};
+
+static struct bset_search_iter bset_search_write_set(struct btree *b,
+                                                     struct bset_tree *t,
+                                                     const struct bkey *search)
+{
+        unsigned li = 0, ri = t->size;
+
+        BUG_ON(!b->nsets &&
+               t->size < bkey_to_cacheline(t, end(t->data)));
+
+        while (li + 1 != ri) {
+                unsigned m = (li + ri) >> 1;
+
+                if (bkey_cmp(table_to_bkey(t, m), search) > 0)
+                        ri = m;
+                else
+                        li = m;
+        }
+
+        return (struct bset_search_iter) {
+                table_to_bkey(t, li),
+                ri < t->size ? table_to_bkey(t, ri) : end(t->data)
+        };
+}
+
+static struct bset_search_iter bset_search_tree(struct btree *b,
+                                                struct bset_tree *t,
+                                                const struct bkey *search)
+{
+        struct bkey *l, *r;
+        struct bkey_float *f;
+        unsigned inorder, j, n = 1;
+
+        do {
+                unsigned p = n << 4;
+                p &= ((int) (p - t->size)) >> 31;
+
+                prefetch(&t->tree[p]);
+
+                j = n;
+                f = &t->tree[j];
+
+                /*
+                 * n = (f->mantissa > bfloat_mantissa())
+                 *      ? j * 2
+                 *      : j * 2 + 1;
+                 *
+                 * We need to subtract 1 from f->mantissa for the sign bit trick
+                 * to work  - that's done in make_bfloat()
+                 */
+                if (likely(f->exponent != 127))
+                        n = j * 2 + (((unsigned)
+                                      (f->mantissa -
+                                       bfloat_mantissa(search, f))) >> 31);
+                else
+                        n = (bkey_cmp(tree_to_bkey(t, j), search) > 0)
+                                ? j * 2
+                                : j * 2 + 1;
+        } while (n < t->size);
+
+        inorder = to_inorder(j, t);
+
+        /*
+         * n would have been the node we recursed to - the low bit tells us if
+         * we recursed left or recursed right.
+         */
+        if (n & 1) {
+                l = cacheline_to_bkey(t, inorder, f->m);
+
+                if (++inorder != t->size) {
+                        f = &t->tree[inorder_next(j, t->size)];
+                        r = cacheline_to_bkey(t, inorder, f->m);
+                } else
+                        r = end(t->data);
+        } else {
+                r = cacheline_to_bkey(t, inorder, f->m);
+
+                if (--inorder) {
+                        f = &t->tree[inorder_prev(j, t->size)];
+                        l = cacheline_to_bkey(t, inorder, f->m);
+                } else
+                        l = t->data->start;
+        }
+
+        return (struct bset_search_iter) {l, r};
+}
+
+struct bkey *__bch_bset_search(struct btree *b, struct bset_tree *t,
+                               const struct bkey *search)
+{
+        struct bset_search_iter i;
+
+        /*
+         * First, we search for a cacheline, then lastly we do a linear search
+         * within that cacheline.
+         *
+         * To search for the cacheline, there's three different possibilities:
+         *  * The set is too small to have a search tree, so we just do a linear
+         *    search over the whole set.
+         *  * The set is the one we're currently inserting into; keeping a full
+         *    auxiliary search tree up to date would be too expensive, so we
+         *    use a much simpler lookup table to do a binary search -
+         *    bset_search_write_set().
+         *  * Or we use the auxiliary search tree we constructed earlier -
+         *    bset_search_tree()
+         */
+
+        if (unlikely(!t->size)) {
+                i.l = t->data->start;
+                i.r = end(t->data);
+        } else if (bset_written(b, t)) {
+                /*
+                 * Each node in the auxiliary search tree covers a certain range
+                 * of bits, and keys above and below the set it covers might
+                 * differ outside those bits - so we have to special case the
+                 * start and end - handle that here:
+                 */
+
+                if (unlikely(bkey_cmp(search, &t->end) >= 0))
+                        return end(t->data);
+
+                if (unlikely(bkey_cmp(search, t->data->start) < 0))
+                        return t->data->start;
+
+                i = bset_search_tree(b, t, search);
+        } else
+                i = bset_search_write_set(b, t, search);
+
+#ifdef CONFIG_BCACHE_EDEBUG
+        BUG_ON(bset_written(b, t) &&
+               i.l != t->data->start &&
+               bkey_cmp(tree_to_prev_bkey(t,
+                  inorder_to_tree(bkey_to_cacheline(t, i.l), t)),
+                        search) > 0);
+
+        BUG_ON(i.r != end(t->data) &&
+               bkey_cmp(i.r, search) <= 0);
+#endif
+
+        while (likely(i.l != i.r) &&
+               bkey_cmp(i.l, search) <= 0)
+                i.l = bkey_next(i.l);
+
+        return i.l;
+}
+
+/* Btree iterator */
+
+static inline bool btree_iter_cmp(struct btree_iter_set l,
+                                  struct btree_iter_set r)
+{
+        int64_t c = bkey_cmp(&START_KEY(l.k), &START_KEY(r.k));
+
+        return c ? c > 0 : l.k < r.k;
+}
+
+static inline bool btree_iter_end(struct btree_iter *iter)
+{
+        return !iter->used;
+}
+
+void bch_btree_iter_push(struct btree_iter *iter, struct bkey *k,
+                         struct bkey *end)
+{
+        if (k != end)
+                BUG_ON(!heap_add(iter,
+                                 ((struct btree_iter_set) { k, end }),
+                                 btree_iter_cmp));
+}
+
+struct bkey *__bch_btree_iter_init(struct btree *b, struct btree_iter *iter,
+                               struct bkey *search, struct bset_tree *start)
+{
+        struct bkey *ret = NULL;
+        iter->size = ARRAY_SIZE(iter->data);
+        iter->used = 0;
+
+        for (; start <= &b->sets[b->nsets]; start++) {
+                ret = bch_bset_search(b, start, search);
+                bch_btree_iter_push(iter, ret, end(start->data));
+        }
+
+        return ret;
+}
+
+struct bkey *bch_btree_iter_next(struct btree_iter *iter)
+{
+        struct btree_iter_set unused;
+        struct bkey *ret = NULL;
+
+        if (!btree_iter_end(iter)) {
+                ret = iter->data->k;
+                iter->data->k = bkey_next(iter->data->k);
+
+                if (iter->data->k > iter->data->end) {
+                        __WARN();
+                        iter->data->k = iter->data->end;
+                }
+
+                if (iter->data->k == iter->data->end)
+                        heap_pop(iter, unused, btree_iter_cmp);
+                else
+                        heap_sift(iter, 0, btree_iter_cmp);
+        }
+
+        return ret;
+}
+
+struct bkey *bch_btree_iter_next_filter(struct btree_iter *iter,
+                                        struct btree *b, ptr_filter_fn fn)
+{
+        struct bkey *ret;
+
+        do {
+                ret = bch_btree_iter_next(iter);
+        } while (ret && fn(b, ret));
+
+        return ret;
+}
+
+struct bkey *bch_next_recurse_key(struct btree *b, struct bkey *search)
+{
+        struct btree_iter iter;
+
+        bch_btree_iter_init(b, &iter, search);
+        return bch_btree_iter_next_filter(&iter, b, bch_ptr_bad);
+}
+
+/* Mergesort */
+
+static void btree_sort_fixup(struct btree_iter *iter)
+{
+        while (iter->used > 1) {
+                struct btree_iter_set *top = iter->data, *i = top + 1;
+                struct bkey *k;
+
+                if (iter->used > 2 &&
+                    btree_iter_cmp(i[0], i[1]))
+                        i++;
+
+                for (k = i->k;
+                     k != i->end && bkey_cmp(top->k, &START_KEY(k)) > 0;
+                     k = bkey_next(k))
+                        if (top->k > i->k)
+                                __bch_cut_front(top->k, k);
+                        else if (KEY_SIZE(k))
+                                bch_cut_back(&START_KEY(k), top->k);
+
+                if (top->k < i->k || k == i->k)
+                        break;
+
+                heap_sift(iter, i - top, btree_iter_cmp);
+        }
+}
+
+static void btree_mergesort(struct btree *b, struct bset *out,
+                            struct btree_iter *iter,
+                            bool fixup, bool remove_stale)
+{
+        struct bkey *k, *last = NULL;
+        bool (*bad)(struct btree *, const struct bkey *) = remove_stale
+                ? bch_ptr_bad
+                : bch_ptr_invalid;
+
+        while (!btree_iter_end(iter)) {
+                if (fixup && !b->level)
+                        btree_sort_fixup(iter);
+
+                k = bch_btree_iter_next(iter);
+                if (bad(b, k))
+                        continue;
+
+                if (!last) {
+                        last = out->start;
+                        bkey_copy(last, k);
+                } else if (b->level ||
+                           !bch_bkey_try_merge(b, last, k)) {
+                        last = bkey_next(last);
+                        bkey_copy(last, k);
+                }
+        }
+
+        out->keys = last ? (uint64_t *) bkey_next(last) - out->d : 0;
+
+        pr_debug("sorted %i keys", out->keys);
+        bch_check_key_order(b, out);
+}
+
+static void __btree_sort(struct btree *b, struct btree_iter *iter,
+                         unsigned start, unsigned order, bool fixup)
+{
+        uint64_t start_time;
+        bool remove_stale = !b->written;
+        struct bset *out = (void *) __get_free_pages(__GFP_NOWARN|GFP_NOIO,
+                                                     order);
+        if (!out) {
+                mutex_lock(&b->c->sort_lock);
+                out = b->c->sort;
+                order = ilog2(bucket_pages(b->c));
+        }
+
+        start_time = local_clock();
+
+        btree_mergesort(b, out, iter, fixup, remove_stale);
+        b->nsets = start;
+
+        if (!fixup && !start && b->written)
+                bch_btree_verify(b, out);
+
+        if (!start && order == b->page_order) {
+                /*
+                 * Our temporary buffer is the same size as the btree node's
+                 * buffer, we can just swap buffers instead of doing a big
+                 * memcpy()
+                 */
+
+                out->magic      = bset_magic(b->c);
+                out->seq        = b->sets[0].data->seq;
+                out->version    = b->sets[0].data->version;
+                swap(out, b->sets[0].data);
+
+                if (b->c->sort == b->sets[0].data)
+                        b->c->sort = out;
+        } else {
+                b->sets[start].data->keys = out->keys;
+                memcpy(b->sets[start].data->start, out->start,
+                       (void *) end(out) - (void *) out->start);
+        }
+
+        if (out == b->c->sort)
+                mutex_unlock(&b->c->sort_lock);
+        else
+                free_pages((unsigned long) out, order);
+
+        if (b->written)
+                bset_build_written_tree(b);
+
+        if (!start) {
+                spin_lock(&b->c->sort_time_lock);
+                time_stats_update(&b->c->sort_time, start_time);
+                spin_unlock(&b->c->sort_time_lock);
+        }
+}
+
+void bch_btree_sort_partial(struct btree *b, unsigned start)
+{
+        size_t oldsize = 0, order = b->page_order, keys = 0;
+        struct btree_iter iter;
+        __bch_btree_iter_init(b, &iter, NULL, &b->sets[start]);
+
+        BUG_ON(b->sets[b->nsets].data == write_block(b) &&
+               (b->sets[b->nsets].size || b->nsets));
+
+        if (b->written)
+                oldsize = bch_count_data(b);
+
+        if (start) {
+                unsigned i;
+
+                for (i = start; i <= b->nsets; i++)
+                        keys += b->sets[i].data->keys;
+
+                order = roundup_pow_of_two(__set_bytes(b->sets->data, keys)) / PAGE_SIZE;
+                if (order)
+                        order = ilog2(order);
+        }
+
+        __btree_sort(b, &iter, start, order, false);
+
+        EBUG_ON(b->written && bch_count_data(b) != oldsize);
+}
+
+void bch_btree_sort_and_fix_extents(struct btree *b, struct btree_iter *iter)
+{
+        BUG_ON(!b->written);
+        __btree_sort(b, iter, 0, b->page_order, true);
+}
+
+void bch_btree_sort_into(struct btree *b, struct btree *new)
+{
+        uint64_t start_time = local_clock();
+
+        struct btree_iter iter;
+        bch_btree_iter_init(b, &iter, NULL);
+
+        btree_mergesort(b, new->sets->data, &iter, false, true);
+
+        spin_lock(&b->c->sort_time_lock);
+        time_stats_update(&b->c->sort_time, start_time);
+        spin_unlock(&b->c->sort_time_lock);
+
+        bkey_copy_key(&new->key, &b->key);
+        new->sets->size = 0;
+}
+
+void bch_btree_sort_lazy(struct btree *b)
+{
+        if (b->nsets) {
+                unsigned i, j, keys = 0, total;
+
+                for (i = 0; i <= b->nsets; i++)
+                        keys += b->sets[i].data->keys;
+
+                total = keys;
+
+                for (j = 0; j < b->nsets; j++) {
+                        if (keys * 2 < total ||
+                            keys < 1000) {
+                                bch_btree_sort_partial(b, j);
+                                return;
+                        }
+
+                        keys -= b->sets[j].data->keys;
+                }
+
+                /* Must sort if b->nsets == 3 or we'll overflow */
+                if (b->nsets >= (MAX_BSETS - 1) - b->level) {
+                        bch_btree_sort(b);
+                        return;
+                }
+        }
+
+        bset_build_written_tree(b);
+}
+
+/* Sysfs stuff */
+
+struct bset_stats {
+        size_t nodes;
+        size_t sets_written, sets_unwritten;
+        size_t bytes_written, bytes_unwritten;
+        size_t floats, failed;
+};
+
+static int bch_btree_bset_stats(struct btree *b, struct btree_op *op,
+                            struct bset_stats *stats)
+{
+        struct bkey *k;
+        unsigned i;
+
+        stats->nodes++;
+
+        for (i = 0; i <= b->nsets; i++) {
+                struct bset_tree *t = &b->sets[i];
+                size_t bytes = t->data->keys * sizeof(uint64_t);
+                size_t j;
+
+                if (bset_written(b, t)) {
+                        stats->sets_written++;
+                        stats->bytes_written += bytes;
+
+                        stats->floats += t->size - 1;
+
+                        for (j = 1; j < t->size; j++)
+                                if (t->tree[j].exponent == 127)
+                                        stats->failed++;
+                } else {
+                        stats->sets_unwritten++;
+                        stats->bytes_unwritten += bytes;
+                }
+        }
+
+        if (b->level) {
+                struct btree_iter iter;
+
+                for_each_key_filter(b, k, &iter, bch_ptr_bad) {
+                        int ret = btree(bset_stats, k, b, op, stats);
+                        if (ret)
+                                return ret;
+                }
+        }
+
+        return 0;
+}
+
+int bch_bset_print_stats(struct cache_set *c, char *buf)
+{
+        struct btree_op op;
+        struct bset_stats t;
+        int ret;
+
+        bch_btree_op_init_stack(&op);
+        memset(&t, 0, sizeof(struct bset_stats));
+
+        ret = btree_root(bset_stats, c, &op, &t);
+        if (ret)
+                return ret;
+
+        return snprintf(buf, PAGE_SIZE,
+                        "btree nodes:           %zu\n"
+                        "written sets:          %zu\n"
+                        "unwritten sets:                %zu\n"
+                        "written key bytes:     %zu\n"
+                        "unwritten key bytes:   %zu\n"
+                        "floats:                        %zu\n"
+                        "failed:                        %zu\n",
+                        t.nodes,
+                        t.sets_written, t.sets_unwritten,
+                        t.bytes_written, t.bytes_unwritten,
+                        t.floats, t.failed);
+}
diff --git a/drivers/md/bcache/bset.h b/drivers/md/bcache/bset.h
new file mode 100644
index 000000000000..57a9cff41546
--- /dev/null
+++ b/drivers/md/bcache/bset.h
@@ -0,0 +1,379 @@
+#ifndef _BCACHE_BSET_H
+#define _BCACHE_BSET_H
+
+/*
+ * BKEYS:
+ *
+ * A bkey contains a key, a size field, a variable number of pointers, and some
+ * ancillary flag bits.
+ *
+ * We use two different functions for validating bkeys, bch_ptr_invalid and
+ * bch_ptr_bad().
+ *
+ * bch_ptr_invalid() primarily filters out keys and pointers that would be
+ * invalid due to some sort of bug, whereas bch_ptr_bad() filters out keys and
+ * pointer that occur in normal practice but don't point to real data.
+ *
+ * The one exception to the rule that ptr_invalid() filters out invalid keys is
+ * that it also filters out keys of size 0 - these are keys that have been
+ * completely overwritten. It'd be safe to delete these in memory while leaving
+ * them on disk, just unnecessary work - so we filter them out when resorting
+ * instead.
+ *
+ * We can't filter out stale keys when we're resorting, because garbage
+ * collection needs to find them to ensure bucket gens don't wrap around -
+ * unless we're rewriting the btree node those stale keys still exist on disk.
+ *
+ * We also implement functions here for removing some number of sectors from the
+ * front or the back of a bkey - this is mainly used for fixing overlapping
+ * extents, by removing the overlapping sectors from the older key.
+ *
+ * BSETS:
+ *
+ * A bset is an array of bkeys laid out contiguously in memory in sorted order,
+ * along with a header. A btree node is made up of a number of these, written at
+ * different times.
+ *
+ * There could be many of them on disk, but we never allow there to be more than
+ * 4 in memory - we lazily resort as needed.
+ *
+ * We implement code here for creating and maintaining auxiliary search trees
+ * (described below) for searching an individial bset, and on top of that we
+ * implement a btree iterator.
+ *
+ * BTREE ITERATOR:
+ *
+ * Most of the code in bcache doesn't care about an individual bset - it needs
+ * to search entire btree nodes and iterate over them in sorted order.
+ *
+ * The btree iterator code serves both functions; it iterates through the keys
+ * in a btree node in sorted order, starting from either keys after a specific
+ * point (if you pass it a search key) or the start of the btree node.
+ *
+ * AUXILIARY SEARCH TREES:
+ *
+ * Since keys are variable length, we can't use a binary search on a bset - we
+ * wouldn't be able to find the start of the next key. But binary searches are
+ * slow anyways, due to terrible cache behaviour; bcache originally used binary
+ * searches and that code topped out at under 50k lookups/second.
+ *
+ * So we need to construct some sort of lookup table. Since we only insert keys
+ * into the last (unwritten) set, most of the keys within a given btree node are
+ * usually in sets that are mostly constant. We use two different types of
+ * lookup tables to take advantage of this.
+ *
+ * Both lookup tables share in common that they don't index every key in the
+ * set; they index one key every BSET_CACHELINE bytes, and then a linear search
+ * is used for the rest.
+ *
+ * For sets that have been written to disk and are no longer being inserted
+ * into, we construct a binary search tree in an array - traversing a binary
+ * search tree in an array gives excellent locality of reference and is very
+ * fast, since both children of any node are adjacent to each other in memory
+ * (and their grandchildren, and great grandchildren...) - this means
+ * prefetching can be used to great effect.
+ *
+ * It's quite useful performance wise to keep these nodes small - not just
+ * because they're more likely to be in L2, but also because we can prefetch
+ * more nodes on a single cacheline and thus prefetch more iterations in advance
+ * when traversing this tree.
+ *
+ * Nodes in the auxiliary search tree must contain both a key to compare against
+ * (we don't want to fetch the key from the set, that would defeat the purpose),
+ * and a pointer to the key. We use a few tricks to compress both of these.
+ *
+ * To compress the pointer, we take advantage of the fact that one node in the
+ * search tree corresponds to precisely BSET_CACHELINE bytes in the set. We have
+ * a function (to_inorder()) that takes the index of a node in a binary tree and
+ * returns what its index would be in an inorder traversal, so we only have to
+ * store the low bits of the offset.
+ *
+ * The key is 84 bits (KEY_DEV + key->key, the offset on the device). To
+ * compress that,  we take advantage of the fact that when we're traversing the
+ * search tree at every iteration we know that both our search key and the key
+ * we're looking for lie within some range - bounded by our previous
+ * comparisons. (We special case the start of a search so that this is true even
+ * at the root of the tree).
+ *
+ * So we know the key we're looking for is between a and b, and a and b don't
+ * differ higher than bit 50, we don't need to check anything higher than bit
+ * 50.
+ *
+ * We don't usually need the rest of the bits, either; we only need enough bits
+ * to partition the key range we're currently checking.  Consider key n - the
+ * key our auxiliary search tree node corresponds to, and key p, the key
+ * immediately preceding n.  The lowest bit we need to store in the auxiliary
+ * search tree is the highest bit that differs between n and p.
+ *
+ * Note that this could be bit 0 - we might sometimes need all 80 bits to do the
+ * comparison. But we'd really like our nodes in the auxiliary search tree to be
+ * of fixed size.
+ *
+ * The solution is to make them fixed size, and when we're constructing a node
+ * check if p and n differed in the bits we needed them to. If they don't we
+ * flag that node, and when doing lookups we fallback to comparing against the
+ * real key. As long as this doesn't happen to often (and it seems to reliably
+ * happen a bit less than 1% of the time), we win - even on failures, that key
+ * is then more likely to be in cache than if we were doing binary searches all
+ * the way, since we're touching so much less memory.
+ *
+ * The keys in the auxiliary search tree are stored in (software) floating
+ * point, with an exponent and a mantissa. The exponent needs to be big enough
+ * to address all the bits in the original key, but the number of bits in the
+ * mantissa is somewhat arbitrary; more bits just gets us fewer failures.
+ *
+ * We need 7 bits for the exponent and 3 bits for the key's offset (since keys
+ * are 8 byte aligned); using 22 bits for the mantissa means a node is 4 bytes.
+ * We need one node per 128 bytes in the btree node, which means the auxiliary
+ * search trees take up 3% as much memory as the btree itself.
+ *
+ * Constructing these auxiliary search trees is moderately expensive, and we
+ * don't want to be constantly rebuilding the search tree for the last set
+ * whenever we insert another key into it. For the unwritten set, we use a much
+ * simpler lookup table - it's just a flat array, so index i in the lookup table
+ * corresponds to the i range of BSET_CACHELINE bytes in the set. Indexing
+ * within each byte range works the same as with the auxiliary search trees.
+ *
+ * These are much easier to keep up to date when we insert a key - we do it
+ * somewhat lazily; when we shift a key up we usually just increment the pointer
+ * to it, only when it would overflow do we go to the trouble of finding the
+ * first key in that range of bytes again.
+ */
+
+/* Btree key comparison/iteration */
+
+struct btree_iter {
+        size_t size, used;
+        struct btree_iter_set {
+                struct bkey *k, *end;
+        } data[MAX_BSETS];
+};
+
+struct bset_tree {
+        /*
+         * We construct a binary tree in an array as if the array
+         * started at 1, so that things line up on the same cachelines
+         * better: see comments in bset.c at cacheline_to_bkey() for
+         * details
+         */
+
+        /* size of the binary tree and prev array */
+        unsigned        size;
+
+        /* function of size - precalculated for to_inorder() */
+        unsigned        extra;
+
+        /* copy of the last key in the set */
+        struct bkey     end;
+        struct bkey_float *tree;
+
+        /*
+         * The nodes in the bset tree point to specific keys - this
+         * array holds the sizes of the previous key.
+         *
+         * Conceptually it's a member of struct bkey_float, but we want
+         * to keep bkey_float to 4 bytes and prev isn't used in the fast
+         * path.
+         */
+        uint8_t         *prev;
+
+        /* The actual btree node, with pointers to each sorted set */
+        struct bset     *data;
+};
+
+static __always_inline int64_t bkey_cmp(const struct bkey *l,
+                                        const struct bkey *r)
+{
+        return unlikely(KEY_INODE(l) != KEY_INODE(r))
+                ? (int64_t) KEY_INODE(l) - (int64_t) KEY_INODE(r)
+                : (int64_t) KEY_OFFSET(l) - (int64_t) KEY_OFFSET(r);
+}
+
+static inline size_t bkey_u64s(const struct bkey *k)
+{
+        BUG_ON(KEY_CSUM(k) > 1);
+        return 2 + KEY_PTRS(k) + (KEY_CSUM(k) ? 1 : 0);
+}
+
+static inline size_t bkey_bytes(const struct bkey *k)
+{
+        return bkey_u64s(k) * sizeof(uint64_t);
+}
+
+static inline void bkey_copy(struct bkey *dest, const struct bkey *src)
+{
+        memcpy(dest, src, bkey_bytes(src));
+}
+
+static inline void bkey_copy_key(struct bkey *dest, const struct bkey *src)
+{
+        if (!src)
+                src = &KEY(0, 0, 0);
+
+        SET_KEY_INODE(dest, KEY_INODE(src));
+        SET_KEY_OFFSET(dest, KEY_OFFSET(src));
+}
+
+static inline struct bkey *bkey_next(const struct bkey *k)
+{
+        uint64_t *d = (void *) k;
+        return (struct bkey *) (d + bkey_u64s(k));
+}
+
+/* Keylists */
+
+struct keylist {
+        struct bkey             *top;
+        union {
+                uint64_t                *list;
+                struct bkey             *bottom;
+        };
+
+        /* Enough room for btree_split's keys without realloc */
+#define KEYLIST_INLINE          16
+        uint64_t                d[KEYLIST_INLINE];
+};
+
+static inline void bch_keylist_init(struct keylist *l)
+{
+        l->top = (void *) (l->list = l->d);
+}
+
+static inline void bch_keylist_push(struct keylist *l)
+{
+        l->top = bkey_next(l->top);
+}
+
+static inline void bch_keylist_add(struct keylist *l, struct bkey *k)
+{
+        bkey_copy(l->top, k);
+        bch_keylist_push(l);
+}
+
+static inline bool bch_keylist_empty(struct keylist *l)
+{
+        return l->top == (void *) l->list;
+}
+
+static inline void bch_keylist_free(struct keylist *l)
+{
+        if (l->list != l->d)
+                kfree(l->list);
+}
+
+void bch_keylist_copy(struct keylist *, struct keylist *);
+struct bkey *bch_keylist_pop(struct keylist *);
+int bch_keylist_realloc(struct keylist *, int, struct cache_set *);
+
+void bch_bkey_copy_single_ptr(struct bkey *, const struct bkey *,
+                              unsigned);
+bool __bch_cut_front(const struct bkey *, struct bkey *);
+bool __bch_cut_back(const struct bkey *, struct bkey *);
+
+static inline bool bch_cut_front(const struct bkey *where, struct bkey *k)
+{
+        BUG_ON(bkey_cmp(where, k) > 0);
+        return __bch_cut_front(where, k);
+}
+
+static inline bool bch_cut_back(const struct bkey *where, struct bkey *k)
+{
+        BUG_ON(bkey_cmp(where, &START_KEY(k)) < 0);
+        return __bch_cut_back(where, k);
+}
+
+const char *bch_ptr_status(struct cache_set *, const struct bkey *);
+bool __bch_ptr_invalid(struct cache_set *, int level, const struct bkey *);
+bool bch_ptr_bad(struct btree *, const struct bkey *);
+
+static inline uint8_t gen_after(uint8_t a, uint8_t b)
+{
+        uint8_t r = a - b;
+        return r > 128U ? 0 : r;
+}
+
+static inline uint8_t ptr_stale(struct cache_set *c, const struct bkey *k,
+                                unsigned i)
+{
+        return gen_after(PTR_BUCKET(c, k, i)->gen, PTR_GEN(k, i));
+}
+
+static inline bool ptr_available(struct cache_set *c, const struct bkey *k,
+                                 unsigned i)
+{
+        return (PTR_DEV(k, i) < MAX_CACHES_PER_SET) && PTR_CACHE(c, k, i);
+}
+
+
+typedef bool (*ptr_filter_fn)(struct btree *, const struct bkey *);
+
+struct bkey *bch_next_recurse_key(struct btree *, struct bkey *);
+struct bkey *bch_btree_iter_next(struct btree_iter *);
+struct bkey *bch_btree_iter_next_filter(struct btree_iter *,
+                                        struct btree *, ptr_filter_fn);
+
+void bch_btree_iter_push(struct btree_iter *, struct bkey *, struct bkey *);
+struct bkey *__bch_btree_iter_init(struct btree *, struct btree_iter *,
+                                   struct bkey *, struct bset_tree *);
+
+/* 32 bits total: */
+#define BKEY_MID_BITS           3
+#define BKEY_EXPONENT_BITS      7
+#define BKEY_MANTISSA_BITS      22
+#define BKEY_MANTISSA_MASK      ((1 << BKEY_MANTISSA_BITS) - 1)
+
+struct bkey_float {
+        unsigned        exponent:BKEY_EXPONENT_BITS;
+        unsigned        m:BKEY_MID_BITS;
+        unsigned        mantissa:BKEY_MANTISSA_BITS;
+} __packed;
+
+/*
+ * BSET_CACHELINE was originally intended to match the hardware cacheline size -
+ * it used to be 64, but I realized the lookup code would touch slightly less
+ * memory if it was 128.
+ *
+ * It definites the number of bytes (in struct bset) per struct bkey_float in
+ * the auxiliar search tree - when we're done searching the bset_float tree we
+ * have this many bytes left that we do a linear search over.
+ *
+ * Since (after level 5) every level of the bset_tree is on a new cacheline,
+ * we're touching one fewer cacheline in the bset tree in exchange for one more
+ * cacheline in the linear search - but the linear search might stop before it
+ * gets to the second cacheline.
+ */
+
+#define BSET_CACHELINE          128
+#define bset_tree_space(b)      (btree_data_space(b) / BSET_CACHELINE)
+
+#define bset_tree_bytes(b)      (bset_tree_space(b) * sizeof(struct bkey_float))
+#define bset_prev_bytes(b)      (bset_tree_space(b) * sizeof(uint8_t))
+
+void bch_bset_init_next(struct btree *);
+
+void bch_bset_fix_invalidated_key(struct btree *, struct bkey *);
+void bch_bset_fix_lookup_table(struct btree *, struct bkey *);
+
+struct bkey *__bch_bset_search(struct btree *, struct bset_tree *,
+                           const struct bkey *);
+
+static inline struct bkey *bch_bset_search(struct btree *b, struct bset_tree *t,
+                                           const struct bkey *search)
+{
+        return search ? __bch_bset_search(b, t, search) : t->data->start;
+}
+
+bool bch_bkey_try_merge(struct btree *, struct bkey *, struct bkey *);
+void bch_btree_sort_lazy(struct btree *);
+void bch_btree_sort_into(struct btree *, struct btree *);
+void bch_btree_sort_and_fix_extents(struct btree *, struct btree_iter *);
+void bch_btree_sort_partial(struct btree *, unsigned);
+
+static inline void bch_btree_sort(struct btree *b)
+{
+        bch_btree_sort_partial(b, 0);
+}
+
+int bch_bset_print_stats(struct cache_set *, char *);
+
+#endif
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
new file mode 100644
index 000000000000..e7bc917ef0d7
--- /dev/null
+++ b/drivers/md/bcache/btree.c
@@ -0,0 +1,2503 @@
+/*
+ * Copyright (C) 2010 Kent Overstreet <kent.overstreet@gmail.com>
+ *
+ * Uses a block device as cache for other block devices; optimized for SSDs.
+ * All allocation is done in buckets, which should match the erase block size
+ * of the device.
+ *
+ * Buckets containing cached data are kept on a heap sorted by priority;
+ * bucket priority is increased on cache hit, and periodically all the buckets
+ * on the heap have their priority scaled down. This currently is just used as
+ * an LRU but in the future should allow for more intelligent heuristics.
+ *
+ * Buckets have an 8 bit counter; freeing is accomplished by incrementing the
+ * counter. Garbage collection is used to remove stale pointers.
+ *
+ * Indexing is done via a btree; nodes are not necessarily fully sorted, rather
+ * as keys are inserted we only sort the pages that have not yet been written.
+ * When garbage collection is run, we resort the entire node.
+ *
+ * All configuration is done via sysfs; see Documentation/bcache.txt.
+ */
+
+#include "bcache.h"
+#include "btree.h"
+#include "debug.h"
+#include "request.h"
+
+#include <linux/slab.h>
+#include <linux/bitops.h>
+#include <linux/hash.h>
+#include <linux/random.h>
+#include <linux/rcupdate.h>
+#include <trace/events/bcache.h>
+
+/*
+ * Todo:
+ * register_bcache: Return errors out to userspace correctly
+ *
+ * Writeback: don't undirty key until after a cache flush
+ *
+ * Create an iterator for key pointers
+ *
+ * On btree write error, mark bucket such that it won't be freed from the cache
+ *
+ * Journalling:
+ *   Check for bad keys in replay
+ *   Propagate barriers
+ *   Refcount journal entries in journal_replay
+ *
+ * Garbage collection:
+ *   Finish incremental gc
+ *   Gc should free old UUIDs, data for invalid UUIDs
+ *
+ * Provide a way to list backing device UUIDs we have data cached for, and
+ * probably how long it's been since we've seen them, and a way to invalidate
+ * dirty data for devices that will never be attached again
+ *
+ * Keep 1 min/5 min/15 min statistics of how busy a block device has been, so
+ * that based on that and how much dirty data we have we can keep writeback
+ * from being starved
+ *
+ * Add a tracepoint or somesuch to watch for writeback starvation
+ *
+ * When btree depth > 1 and splitting an interior node, we have to make sure
+ * alloc_bucket() cannot fail. This should be true but is not completely
+ * obvious.
+ *
+ * Make sure all allocations get charged to the root cgroup
+ *
+ * Plugging?
+ *
+ * If data write is less than hard sector size of ssd, round up offset in open
+ * bucket to the next whole sector
+ *
+ * Also lookup by cgroup in get_open_bucket()
+ *
+ * Superblock needs to be fleshed out for multiple cache devices
+ *
+ * Add a sysfs tunable for the number of writeback IOs in flight
+ *
+ * Add a sysfs tunable for the number of open data buckets
+ *
+ * IO tracking: Can we track when one process is doing io on behalf of another?
+ * IO tracking: Don't use just an average, weigh more recent stuff higher
+ *
+ * Test module load/unload
+ */
+
+static const char * const op_types[] = {
+        "insert", "replace"
+};
+
+static const char *op_type(struct btree_op *op)
+{
+        return op_types[op->type];
+}
+
+#define MAX_NEED_GC             64
+#define MAX_SAVE_PRIO           72
+
+#define PTR_DIRTY_BIT           (((uint64_t) 1 << 36))
+
+#define PTR_HASH(c, k)                                                  \
+        (((k)->ptr[0] >> c->bucket_bits) | PTR_GEN(k, 0))
+
+struct workqueue_struct *bch_gc_wq;
+static struct workqueue_struct *btree_io_wq;
+
+void bch_btree_op_init_stack(struct btree_op *op)
+{
+        memset(op, 0, sizeof(struct btree_op));
+        closure_init_stack(&op->cl);
+        op->lock = -1;
+        bch_keylist_init(&op->keys);
+}
+
+/* Btree key manipulation */
+
+static void bkey_put(struct cache_set *c, struct bkey *k, int level)
+{
+        if ((level && KEY_OFFSET(k)) || !level)
+                __bkey_put(c, k);
+}
+
+/* Btree IO */
+
+static uint64_t btree_csum_set(struct btree *b, struct bset *i)
+{
+        uint64_t crc = b->key.ptr[0];
+        void *data = (void *) i + 8, *end = end(i);
+
+        crc = crc64_update(crc, data, end - data);
+        return crc ^ 0xffffffffffffffff;
+}
+
+static void btree_bio_endio(struct bio *bio, int error)
+{
+        struct closure *cl = bio->bi_private;
+        struct btree *b = container_of(cl, struct btree, io.cl);
+
+        if (error)
+                set_btree_node_io_error(b);
+
+        bch_bbio_count_io_errors(b->c, bio, error, (bio->bi_rw & WRITE)
+                                 ? "writing btree" : "reading btree");
+        closure_put(cl);
+}
+
+static void btree_bio_init(struct btree *b)
+{
+        BUG_ON(b->bio);
+        b->bio = bch_bbio_alloc(b->c);
+
+        b->bio->bi_end_io       = btree_bio_endio;
+        b->bio->bi_private      = &b->io.cl;
+}
+
+void bch_btree_read_done(struct closure *cl)
+{
+        struct btree *b = container_of(cl, struct btree, io.cl);
+        struct bset *i = b->sets[0].data;
+        struct btree_iter *iter = b->c->fill_iter;
+        const char *err = "bad btree header";
+        BUG_ON(b->nsets || b->written);
+
+        bch_bbio_free(b->bio, b->c);
+        b->bio = NULL;
+
+        mutex_lock(&b->c->fill_lock);
+        iter->used = 0;
+
+        if (btree_node_io_error(b) ||
+            !i->seq)
+                goto err;
+
+        for (;
+             b->written < btree_blocks(b) && i->seq == b->sets[0].data->seq;
+             i = write_block(b)) {
+                err = "unsupported bset version";
+                if (i->version > BCACHE_BSET_VERSION)
+                        goto err;
+
+                err = "bad btree header";
+                if (b->written + set_blocks(i, b->c) > btree_blocks(b))
+                        goto err;
+
+                err = "bad magic";
+                if (i->magic != bset_magic(b->c))
+                        goto err;
+
+                err = "bad checksum";
+                switch (i->version) {
+                case 0:
+                        if (i->csum != csum_set(i))
+                                goto err;
+                        break;
+                case BCACHE_BSET_VERSION:
+                        if (i->csum != btree_csum_set(b, i))
+                                goto err;
+                        break;
+                }
+
+                err = "empty set";
+                if (i != b->sets[0].data && !i->keys)
+                        goto err;
+
+                bch_btree_iter_push(iter, i->start, end(i));
+
+                b->written += set_blocks(i, b->c);
+        }
+
+        err = "corrupted btree";
+        for (i = write_block(b);
+             index(i, b) < btree_blocks(b);
+             i = ((void *) i) + block_bytes(b->c))
+                if (i->seq == b->sets[0].data->seq)
+                        goto err;
+
+        bch_btree_sort_and_fix_extents(b, iter);
+
+        i = b->sets[0].data;
+        err = "short btree key";
+        if (b->sets[0].size &&
+            bkey_cmp(&b->key, &b->sets[0].end) < 0)
+                goto err;
+
+        if (b->written < btree_blocks(b))
+                bch_bset_init_next(b);
+out:
+
+        mutex_unlock(&b->c->fill_lock);
+
+        spin_lock(&b->c->btree_read_time_lock);
+        time_stats_update(&b->c->btree_read_time, b->io_start_time);
+        spin_unlock(&b->c->btree_read_time_lock);
+
+        smp_wmb(); /* read_done is our write lock */
+        set_btree_node_read_done(b);
+
+        closure_return(cl);
+err:
+        set_btree_node_io_error(b);
+        bch_cache_set_error(b->c, "%s at bucket %lu, block %zu, %u keys",
+                            err, PTR_BUCKET_NR(b->c, &b->key, 0),
+                            index(i, b), i->keys);
+        goto out;
+}
+
+void bch_btree_read(struct btree *b)
+{
+        BUG_ON(b->nsets || b->written);
+
+        if (!closure_trylock(&b->io.cl, &b->c->cl))
+                BUG();
+
+        b->io_start_time = local_clock();
+
+        btree_bio_init(b);
+        b->bio->bi_rw   = REQ_META|READ_SYNC;
+        b->bio->bi_size = KEY_SIZE(&b->key) << 9;
+
+        bio_map(b->bio, b->sets[0].data);
+
+        pr_debug("%s", pbtree(b));
+        trace_bcache_btree_read(b->bio);
+        bch_submit_bbio(b->bio, b->c, &b->key, 0);
+
+        continue_at(&b->io.cl, bch_btree_read_done, system_wq);
+}
+
+static void btree_complete_write(struct btree *b, struct btree_write *w)
+{
+        if (w->prio_blocked &&
+            !atomic_sub_return(w->prio_blocked, &b->c->prio_blocked))
+                wake_up(&b->c->alloc_wait);
+
+        if (w->journal) {
+                atomic_dec_bug(w->journal);
+                __closure_wake_up(&b->c->journal.wait);
+        }
+
+        if (w->owner)
+                closure_put(w->owner);
+
+        w->prio_blocked = 0;
+        w->journal      = NULL;
+        w->owner        = NULL;
+}
+
+static void __btree_write_done(struct closure *cl)
+{
+        struct btree *b = container_of(cl, struct btree, io.cl);
+        struct btree_write *w = btree_prev_write(b);
+
+        bch_bbio_free(b->bio, b->c);
+        b->bio = NULL;
+        btree_complete_write(b, w);
+
+        if (btree_node_dirty(b))
+                queue_delayed_work(btree_io_wq, &b->work,
+                                   msecs_to_jiffies(30000));
+
+        closure_return(cl);
+}
+
+static void btree_write_done(struct closure *cl)
+{
+        struct btree *b = container_of(cl, struct btree, io.cl);
+        struct bio_vec *bv;
+        int n;
+
+        __bio_for_each_segment(bv, b->bio, n, 0)
+                __free_page(bv->bv_page);
+
+        __btree_write_done(cl);
+}
+
+static void do_btree_write(struct btree *b)
+{
+        struct closure *cl = &b->io.cl;
+        struct bset *i = b->sets[b->nsets].data;
+        BKEY_PADDED(key) k;
+
+        i->version      = BCACHE_BSET_VERSION;
+        i->csum         = btree_csum_set(b, i);
+
+        btree_bio_init(b);
+        b->bio->bi_rw   = REQ_META|WRITE_SYNC;
+        b->bio->bi_size = set_blocks(i, b->c) * block_bytes(b->c);
+        bio_map(b->bio, i);
+
+        bkey_copy(&k.key, &b->key);
+        SET_PTR_OFFSET(&k.key, 0, PTR_OFFSET(&k.key, 0) + bset_offset(b, i));
+
+        if (!bio_alloc_pages(b->bio, GFP_NOIO)) {
+                int j;
+                struct bio_vec *bv;
+                void *base = (void *) ((unsigned long) i & ~(PAGE_SIZE - 1));
+
+                bio_for_each_segment(bv, b->bio, j)
+                        memcpy(page_address(bv->bv_page),
+                               base + j * PAGE_SIZE, PAGE_SIZE);
+
+                trace_bcache_btree_write(b->bio);
+                bch_submit_bbio(b->bio, b->c, &k.key, 0);
+
+                continue_at(cl, btree_write_done, NULL);
+        } else {
+                b->bio->bi_vcnt = 0;
+                bio_map(b->bio, i);
+
+                trace_bcache_btree_write(b->bio);
+                bch_submit_bbio(b->bio, b->c, &k.key, 0);
+
+                closure_sync(cl);
+                __btree_write_done(cl);
+        }
+}
+
+static void __btree_write(struct btree *b)
+{
+        struct bset *i = b->sets[b->nsets].data;
+
+        BUG_ON(current->bio_list);
+
+        closure_lock(&b->io, &b->c->cl);
+        cancel_delayed_work(&b->work);
+
+        clear_bit(BTREE_NODE_dirty,      &b->flags);
+        change_bit(BTREE_NODE_write_idx, &b->flags);
+
+        bch_check_key_order(b, i);
+        BUG_ON(b->written && !i->keys);
+
+        do_btree_write(b);
+
+        pr_debug("%s block %i keys %i", pbtree(b), b->written, i->keys);
+
+        b->written += set_blocks(i, b->c);
+        atomic_long_add(set_blocks(i, b->c) * b->c->sb.block_size,
+                        &PTR_CACHE(b->c, &b->key, 0)->btree_sectors_written);
+
+        bch_btree_sort_lazy(b);
+
+        if (b->written < btree_blocks(b))
+                bch_bset_init_next(b);
+}
+
+static void btree_write_work(struct work_struct *w)
+{
+        struct btree *b = container_of(to_delayed_work(w), struct btree, work);
+
+        down_write(&b->lock);
+
+        if (btree_node_dirty(b))
+                __btree_write(b);
+        up_write(&b->lock);
+}
+
+void bch_btree_write(struct btree *b, bool now, struct btree_op *op)
+{
+        struct bset *i = b->sets[b->nsets].data;
+        struct btree_write *w = btree_current_write(b);
+
+        BUG_ON(b->written &&
+               (b->written >= btree_blocks(b) ||
+                i->seq != b->sets[0].data->seq ||
+                !i->keys));
+
+        if (!btree_node_dirty(b)) {
+                set_btree_node_dirty(b);
+                queue_delayed_work(btree_io_wq, &b->work,
+                                   msecs_to_jiffies(30000));
+        }
+
+        w->prio_blocked += b->prio_blocked;
+        b->prio_blocked = 0;
+
+        if (op && op->journal && !b->level) {
+                if (w->journal &&
+                    journal_pin_cmp(b->c, w, op)) {
+                        atomic_dec_bug(w->journal);
+                        w->journal = NULL;
+                }
+
+                if (!w->journal) {
+                        w->journal = op->journal;
+                        atomic_inc(w->journal);
+                }
+        }
+
+        if (current->bio_list)
+                return;
+
+        /* Force write if set is too big */
+        if (now ||
+            b->level ||
+            set_bytes(i) > PAGE_SIZE - 48) {
+                if (op && now) {
+                        /* Must wait on multiple writes */
+                        BUG_ON(w->owner);
+                        w->owner = &op->cl;
+                        closure_get(&op->cl);
+                }
+
+                __btree_write(b);
+        }
+        BUG_ON(!b->written);
+}
+
+/*
+ * Btree in memory cache - allocation/freeing
+ * mca -> memory cache
+ */
+
+static void mca_reinit(struct btree *b)
+{
+        unsigned i;
+
+        b->flags        = 0;
+        b->written      = 0;
+        b->nsets        = 0;
+
+        for (i = 0; i < MAX_BSETS; i++)
+                b->sets[i].size = 0;
+        /*
+         * Second loop starts at 1 because b->sets[0]->data is the memory we
+         * allocated
+         */
+        for (i = 1; i < MAX_BSETS; i++)
+                b->sets[i].data = NULL;
+}
+
+#define mca_reserve(c)  (((c->root && c->root->level)           \
+                          ? c->root->level : 1) * 8 + 16)
+#define mca_can_free(c)                                         \
+        max_t(int, 0, c->bucket_cache_used - mca_reserve(c))
+
+static void mca_data_free(struct btree *b)
+{
+        struct bset_tree *t = b->sets;
+        BUG_ON(!closure_is_unlocked(&b->io.cl));
+
+        if (bset_prev_bytes(b) < PAGE_SIZE)
+                kfree(t->prev);
+        else
+                free_pages((unsigned long) t->prev,
+                           get_order(bset_prev_bytes(b)));
+
+        if (bset_tree_bytes(b) < PAGE_SIZE)
+                kfree(t->tree);
+        else
+                free_pages((unsigned long) t->tree,
+                           get_order(bset_tree_bytes(b)));
+
+        free_pages((unsigned long) t->data, b->page_order);
+
+        t->prev = NULL;
+        t->tree = NULL;
+        t->data = NULL;
+        list_move(&b->list, &b->c->btree_cache_freed);
+        b->c->bucket_cache_used--;
+}
+
+static void mca_bucket_free(struct btree *b)
+{
+        BUG_ON(btree_node_dirty(b));
+
+        b->key.ptr[0] = 0;
+        hlist_del_init_rcu(&b->hash);
+        list_move(&b->list, &b->c->btree_cache_freeable);
+}
+
+static unsigned btree_order(struct bkey *k)
+{
+        return ilog2(KEY_SIZE(k) / PAGE_SECTORS ?: 1);
+}
+
+static void mca_data_alloc(struct btree *b, struct bkey *k, gfp_t gfp)
+{
+        struct bset_tree *t = b->sets;
+        BUG_ON(t->data);
+
+        b->page_order = max_t(unsigned,
+                              ilog2(b->c->btree_pages),
+                              btree_order(k));
+
+        t->data = (void *) __get_free_pages(gfp, b->page_order);
+        if (!t->data)
+                goto err;
+
+        t->tree = bset_tree_bytes(b) < PAGE_SIZE
+                ? kmalloc(bset_tree_bytes(b), gfp)
+                : (void *) __get_free_pages(gfp, get_order(bset_tree_bytes(b)));
+        if (!t->tree)
+                goto err;
+
+        t->prev = bset_prev_bytes(b) < PAGE_SIZE
+                ? kmalloc(bset_prev_bytes(b), gfp)
+                : (void *) __get_free_pages(gfp, get_order(bset_prev_bytes(b)));
+        if (!t->prev)
+                goto err;
+
+        list_move(&b->list, &b->c->btree_cache);
+        b->c->bucket_cache_used++;
+        return;
+err:
+        mca_data_free(b);
+}
+
+static struct btree *mca_bucket_alloc(struct cache_set *c,
+                                      struct bkey *k, gfp_t gfp)
+{
+        struct btree *b = kzalloc(sizeof(struct btree), gfp);
+        if (!b)
+                return NULL;
+
+        init_rwsem(&b->lock);
+        lockdep_set_novalidate_class(&b->lock);
+        INIT_LIST_HEAD(&b->list);
+        INIT_DELAYED_WORK(&b->work, btree_write_work);
+        b->c = c;
+        closure_init_unlocked(&b->io);
+
+        mca_data_alloc(b, k, gfp);
+        return b;
+}
+
+static int mca_reap(struct btree *b, struct closure *cl, unsigned min_order)
+{
+        lockdep_assert_held(&b->c->bucket_lock);
+
+        if (!down_write_trylock(&b->lock))
+                return -ENOMEM;
+
+        if (b->page_order < min_order) {
+                rw_unlock(true, b);
+                return -ENOMEM;
+        }
+
+        BUG_ON(btree_node_dirty(b) && !b->sets[0].data);
+
+        if (cl && btree_node_dirty(b))
+                bch_btree_write(b, true, NULL);
+
+        if (cl)
+                closure_wait_event_async(&b->io.wait, cl,
+                         atomic_read(&b->io.cl.remaining) == -1);
+
+        if (btree_node_dirty(b) ||
+            !closure_is_unlocked(&b->io.cl) ||
+            work_pending(&b->work.work)) {
+                rw_unlock(true, b);
+                return -EAGAIN;
+        }
+
+        return 0;
+}
+
+static int bch_mca_shrink(struct shrinker *shrink, struct shrink_control *sc)
+{
+        struct cache_set *c = container_of(shrink, struct cache_set, shrink);
+        struct btree *b, *t;
+        unsigned long i, nr = sc->nr_to_scan;
+
+        if (c->shrinker_disabled)
+                return 0;
+
+        if (c->try_harder)
+                return 0;
+
+        /*
+         * If nr == 0, we're supposed to return the number of items we have
+         * cached. Not allowed to return -1.
+         */
+        if (!nr)
+                return mca_can_free(c) * c->btree_pages;
+
+        /* Return -1 if we can't do anything right now */
+        if (sc->gfp_mask & __GFP_WAIT)
+                mutex_lock(&c->bucket_lock);
+        else if (!mutex_trylock(&c->bucket_lock))
+                return -1;
+
+        nr /= c->btree_pages;
+        nr = min_t(unsigned long, nr, mca_can_free(c));
+
+        i = 0;
+        list_for_each_entry_safe(b, t, &c->btree_cache_freeable, list) {
+                if (!nr)
+                        break;
+
+                if (++i > 3 &&
+                    !mca_reap(b, NULL, 0)) {
+                        mca_data_free(b);
+                        rw_unlock(true, b);
+                        --nr;
+                }
+        }
+
+        /*
+         * Can happen right when we first start up, before we've read in any
+         * btree nodes
+         */
+        if (list_empty(&c->btree_cache))
+                goto out;
+
+        for (i = 0; nr && i < c->bucket_cache_used; i++) {
+                b = list_first_entry(&c->btree_cache, struct btree, list);
+                list_rotate_left(&c->btree_cache);
+
+                if (!b->accessed &&
+                    !mca_reap(b, NULL, 0)) {
+                        mca_bucket_free(b);
+                        mca_data_free(b);
+                        rw_unlock(true, b);
+                        --nr;
+                } else
+                        b->accessed = 0;
+        }
+out:
+        nr = mca_can_free(c) * c->btree_pages;
+        mutex_unlock(&c->bucket_lock);
+        return nr;
+}
+
+void bch_btree_cache_free(struct cache_set *c)
+{
+        struct btree *b;
+        struct closure cl;
+        closure_init_stack(&cl);
+
+        if (c->shrink.list.next)
+                unregister_shrinker(&c->shrink);
+
+        mutex_lock(&c->bucket_lock);
+
+#ifdef CONFIG_BCACHE_DEBUG
+        if (c->verify_data)
+                list_move(&c->verify_data->list, &c->btree_cache);
+#endif
+
+        list_splice(&c->btree_cache_freeable,
+                    &c->btree_cache);
+
+        while (!list_empty(&c->btree_cache)) {
+                b = list_first_entry(&c->btree_cache, struct btree, list);
+
+                if (btree_node_dirty(b))
+                        btree_complete_write(b, btree_current_write(b));
+                clear_bit(BTREE_NODE_dirty, &b->flags);
+
+                mca_data_free(b);
+        }
+
+        while (!list_empty(&c->btree_cache_freed)) {
+                b = list_first_entry(&c->btree_cache_freed,
+                                     struct btree, list);
+                list_del(&b->list);
+                cancel_delayed_work_sync(&b->work);
+                kfree(b);
+        }
+
+        mutex_unlock(&c->bucket_lock);
+}
+
+int bch_btree_cache_alloc(struct cache_set *c)
+{
+        unsigned i;
+
+        /* XXX: doesn't check for errors */
+
+        closure_init_unlocked(&c->gc);
+
+        for (i = 0; i < mca_reserve(c); i++)
+                mca_bucket_alloc(c, &ZERO_KEY, GFP_KERNEL);
+
+        list_splice_init(&c->btree_cache,
+                         &c->btree_cache_freeable);
+
+#ifdef CONFIG_BCACHE_DEBUG
+        mutex_init(&c->verify_lock);
+
+        c->verify_data = mca_bucket_alloc(c, &ZERO_KEY, GFP_KERNEL);
+
+        if (c->verify_data &&
+            c->verify_data->sets[0].data)
+                list_del_init(&c->verify_data->list);
+        else
+                c->verify_data = NULL;
+#endif
+
+        c->shrink.shrink = bch_mca_shrink;
+        c->shrink.seeks = 4;
+        c->shrink.batch = c->btree_pages * 2;
+        register_shrinker(&c->shrink);
+
+        return 0;
+}
+
+/* Btree in memory cache - hash table */
+
+static struct hlist_head *mca_hash(struct cache_set *c, struct bkey *k)
+{
+        return &c->bucket_hash[hash_32(PTR_HASH(c, k), BUCKET_HASH_BITS)];
+}
+
+static struct btree *mca_find(struct cache_set *c, struct bkey *k)
+{
+        struct btree *b;
+
+        rcu_read_lock();
+        hlist_for_each_entry_rcu(b, mca_hash(c, k), hash)
+                if (PTR_HASH(c, &b->key) == PTR_HASH(c, k))
+                        goto out;
+        b = NULL;
+out:
+        rcu_read_unlock();
+        return b;
+}
+
+static struct btree *mca_cannibalize(struct cache_set *c, struct bkey *k,
+                                     int level, struct closure *cl)
+{
+        int ret = -ENOMEM;
+        struct btree *i;
+
+        if (!cl)
+                return ERR_PTR(-ENOMEM);
+
+        /*
+         * Trying to free up some memory - i.e. reuse some btree nodes - may
+         * require initiating IO to flush the dirty part of the node. If we're
+         * running under generic_make_request(), that IO will never finish and
+         * we would deadlock. Returning -EAGAIN causes the cache lookup code to
+         * punt to workqueue and retry.
+         */
+        if (current->bio_list)
+                return ERR_PTR(-EAGAIN);
+
+        if (c->try_harder && c->try_harder != cl) {
+                closure_wait_event_async(&c->try_wait, cl, !c->try_harder);
+                return ERR_PTR(-EAGAIN);
+        }
+
+        /* XXX: tracepoint */
+        c->try_harder = cl;
+        c->try_harder_start = local_clock();
+retry:
+        list_for_each_entry_reverse(i, &c->btree_cache, list) {
+                int r = mca_reap(i, cl, btree_order(k));
+                if (!r)
+                        return i;
+                if (r != -ENOMEM)
+                        ret = r;
+        }
+
+        if (ret == -EAGAIN &&
+            closure_blocking(cl)) {
+                mutex_unlock(&c->bucket_lock);
+                closure_sync(cl);
+                mutex_lock(&c->bucket_lock);
+                goto retry;
+        }
+
+        return ERR_PTR(ret);
+}
+
+/*
+ * We can only have one thread cannibalizing other cached btree nodes at a time,
+ * or we'll deadlock. We use an open coded mutex to ensure that, which a
+ * cannibalize_bucket() will take. This means every time we unlock the root of
+ * the btree, we need to release this lock if we have it held.
+ */
+void bch_cannibalize_unlock(struct cache_set *c, struct closure *cl)
+{
+        if (c->try_harder == cl) {
+                time_stats_update(&c->try_harder_time, c->try_harder_start);
+                c->try_harder = NULL;
+                __closure_wake_up(&c->try_wait);
+        }
+}
+
+static struct btree *mca_alloc(struct cache_set *c, struct bkey *k,
+                               int level, struct closure *cl)
+{
+        struct btree *b;
+
+        lockdep_assert_held(&c->bucket_lock);
+
+        if (mca_find(c, k))
+                return NULL;
+
+        /* btree_free() doesn't free memory; it sticks the node on the end of
+         * the list. Check if there's any freed nodes there:
+         */
+        list_for_each_entry(b, &c->btree_cache_freeable, list)
+                if (!mca_reap(b, NULL, btree_order(k)))
+                        goto out;
+
+        /* We never free struct btree itself, just the memory that holds the on
+         * disk node. Check the freed list before allocating a new one:
+         */
+        list_for_each_entry(b, &c->btree_cache_freed, list)
+                if (!mca_reap(b, NULL, 0)) {
+                        mca_data_alloc(b, k, __GFP_NOWARN|GFP_NOIO);
+                        if (!b->sets[0].data)
+                                goto err;
+                        else
+                                goto out;
+                }
+
+        b = mca_bucket_alloc(c, k, __GFP_NOWARN|GFP_NOIO);
+        if (!b)
+                goto err;
+
+        BUG_ON(!down_write_trylock(&b->lock));
+        if (!b->sets->data)
+                goto err;
+out:
+        BUG_ON(!closure_is_unlocked(&b->io.cl));
+
+        bkey_copy(&b->key, k);
+        list_move(&b->list, &c->btree_cache);
+        hlist_del_init_rcu(&b->hash);
+        hlist_add_head_rcu(&b->hash, mca_hash(c, k));
+
+        lock_set_subclass(&b->lock.dep_map, level + 1, _THIS_IP_);
+        b->level        = level;
+
+        mca_reinit(b);
+
+        return b;
+err:
+        if (b)
+                rw_unlock(true, b);
+
+        b = mca_cannibalize(c, k, level, cl);
+        if (!IS_ERR(b))
+                goto out;
+
+        return b;
+}
+
+/**
+ * bch_btree_node_get - find a btree node in the cache and lock it, reading it
+ * in from disk if necessary.
+ *
+ * If IO is necessary, it uses the closure embedded in struct btree_op to wait;
+ * if that closure is in non blocking mode, will return -EAGAIN.
+ *
+ * The btree node will have either a read or a write lock held, depending on
+ * level and op->lock.
+ */
+struct btree *bch_btree_node_get(struct cache_set *c, struct bkey *k,
+                                 int level, struct btree_op *op)
+{
+        int i = 0;
+        bool write = level <= op->lock;
+        struct btree *b;
+
+        BUG_ON(level < 0);
+retry:
+        b = mca_find(c, k);
+
+        if (!b) {
+                mutex_lock(&c->bucket_lock);
+                b = mca_alloc(c, k, level, &op->cl);
+                mutex_unlock(&c->bucket_lock);
+
+                if (!b)
+                        goto retry;
+                if (IS_ERR(b))
+                        return b;
+
+                bch_btree_read(b);
+
+                if (!write)
+                        downgrade_write(&b->lock);
+        } else {
+                rw_lock(write, b, level);
+                if (PTR_HASH(c, &b->key) != PTR_HASH(c, k)) {
+                        rw_unlock(write, b);
+                        goto retry;
+                }
+                BUG_ON(b->level != level);
+        }
+
+        b->accessed = 1;
+
+        for (; i <= b->nsets && b->sets[i].size; i++) {
+                prefetch(b->sets[i].tree);
+                prefetch(b->sets[i].data);
+        }
+
+        for (; i <= b->nsets; i++)
+                prefetch(b->sets[i].data);
+
+        if (!closure_wait_event(&b->io.wait, &op->cl,
+                                btree_node_read_done(b))) {
+                rw_unlock(write, b);
+                b = ERR_PTR(-EAGAIN);
+        } else if (btree_node_io_error(b)) {
+                rw_unlock(write, b);
+                b = ERR_PTR(-EIO);
+        } else
+                BUG_ON(!b->written);
+
+        return b;
+}
+
+static void btree_node_prefetch(struct cache_set *c, struct bkey *k, int level)
+{
+        struct btree *b;
+
+        mutex_lock(&c->bucket_lock);
+        b = mca_alloc(c, k, level, NULL);
+        mutex_unlock(&c->bucket_lock);
+
+        if (!IS_ERR_OR_NULL(b)) {
+                bch_btree_read(b);
+                rw_unlock(true, b);
+        }
+}
+
+/* Btree alloc */
+
+static void btree_node_free(struct btree *b, struct btree_op *op)
+{
+        unsigned i;
+
+        /*
+         * The BUG_ON() in btree_node_get() implies that we must have a write
+         * lock on parent to free or even invalidate a node
+         */
+        BUG_ON(op->lock <= b->level);
+        BUG_ON(b == b->c->root);
+        pr_debug("bucket %s", pbtree(b));
+
+        if (btree_node_dirty(b))
+                btree_complete_write(b, btree_current_write(b));
+        clear_bit(BTREE_NODE_dirty, &b->flags);
+
+        if (b->prio_blocked &&
+            !atomic_sub_return(b->prio_blocked, &b->c->prio_blocked))
+                closure_wake_up(&b->c->bucket_wait);
+
+        b->prio_blocked = 0;
+
+        cancel_delayed_work(&b->work);
+
+        mutex_lock(&b->c->bucket_lock);
+
+        for (i = 0; i < KEY_PTRS(&b->key); i++) {
+                BUG_ON(atomic_read(&PTR_BUCKET(b->c, &b->key, i)->pin));
+
+                bch_inc_gen(PTR_CACHE(b->c, &b->key, i),
+                            PTR_BUCKET(b->c, &b->key, i));
+        }
+
+        bch_bucket_free(b->c, &b->key);
+        mca_bucket_free(b);
+        mutex_unlock(&b->c->bucket_lock);
+}
+
+struct btree *bch_btree_node_alloc(struct cache_set *c, int level,
+                                   struct closure *cl)
+{
+        BKEY_PADDED(key) k;
+        struct btree *b = ERR_PTR(-EAGAIN);
+
+        mutex_lock(&c->bucket_lock);
+retry:
+        if (__bch_bucket_alloc_set(c, WATERMARK_METADATA, &k.key, 1, cl))
+                goto err;
+
+        SET_KEY_SIZE(&k.key, c->btree_pages * PAGE_SECTORS);
+
+        b = mca_alloc(c, &k.key, level, cl);
+        if (IS_ERR(b))
+                goto err_free;
+
+        if (!b) {
+                cache_bug(c, "Tried to allocate bucket"
+                          " that was in btree cache");
+                __bkey_put(c, &k.key);
+                goto retry;
+        }
+
+        set_btree_node_read_done(b);
+        b->accessed = 1;
+        bch_bset_init_next(b);
+
+        mutex_unlock(&c->bucket_lock);
+        return b;
+err_free:
+        bch_bucket_free(c, &k.key);
+        __bkey_put(c, &k.key);
+err:
+        mutex_unlock(&c->bucket_lock);
+        return b;
+}
+
+static struct btree *btree_node_alloc_replacement(struct btree *b,
+                                                  struct closure *cl)
+{
+        struct btree *n = bch_btree_node_alloc(b->c, b->level, cl);
+        if (!IS_ERR_OR_NULL(n))
+                bch_btree_sort_into(b, n);
+
+        return n;
+}
+
+/* Garbage collection */
+
+uint8_t __bch_btree_mark_key(struct cache_set *c, int level, struct bkey *k)
+{
+        uint8_t stale = 0;
+        unsigned i;
+        struct bucket *g;
+
+        /*
+         * ptr_invalid() can't return true for the keys that mark btree nodes as
+         * freed, but since ptr_bad() returns true we'll never actually use them
+         * for anything and thus we don't want mark their pointers here
+         */
+        if (!bkey_cmp(k, &ZERO_KEY))
+                return stale;
+
+        for (i = 0; i < KEY_PTRS(k); i++) {
+                if (!ptr_available(c, k, i))
+                        continue;
+
+                g = PTR_BUCKET(c, k, i);
+
+                if (gen_after(g->gc_gen, PTR_GEN(k, i)))
+                        g->gc_gen = PTR_GEN(k, i);
+
+                if (ptr_stale(c, k, i)) {
+                        stale = max(stale, ptr_stale(c, k, i));
+                        continue;
+                }
+
+                cache_bug_on(GC_MARK(g) &&
+                             (GC_MARK(g) == GC_MARK_METADATA) != (level != 0),
+                             c, "inconsistent ptrs: mark = %llu, level = %i",
+                             GC_MARK(g), level);
+
+                if (level)
+                        SET_GC_MARK(g, GC_MARK_METADATA);
+                else if (KEY_DIRTY(k))
+                        SET_GC_MARK(g, GC_MARK_DIRTY);
+
+                /* guard against overflow */
+                SET_GC_SECTORS_USED(g, min_t(unsigned,
+                                             GC_SECTORS_USED(g) + KEY_SIZE(k),
+                                             (1 << 14) - 1));
+
+                BUG_ON(!GC_SECTORS_USED(g));
+        }
+
+        return stale;
+}
+
+#define btree_mark_key(b, k)    __bch_btree_mark_key(b->c, b->level, k)
+
+static int btree_gc_mark_node(struct btree *b, unsigned *keys,
+                              struct gc_stat *gc)
+{
+        uint8_t stale = 0;
+        unsigned last_dev = -1;
+        struct bcache_device *d = NULL;
+        struct bkey *k;
+        struct btree_iter iter;
+        struct bset_tree *t;
+
+        gc->nodes++;
+
+        for_each_key_filter(b, k, &iter, bch_ptr_invalid) {
+                if (last_dev != KEY_INODE(k)) {
+                        last_dev = KEY_INODE(k);
+
+                        d = KEY_INODE(k) < b->c->nr_uuids
+                                ? b->c->devices[last_dev]
+                                : NULL;
+                }
+
+                stale = max(stale, btree_mark_key(b, k));
+
+                if (bch_ptr_bad(b, k))
+                        continue;
+
+                *keys += bkey_u64s(k);
+
+                gc->key_bytes += bkey_u64s(k);
+                gc->nkeys++;
+
+                gc->data += KEY_SIZE(k);
+                if (KEY_DIRTY(k)) {
+                        gc->dirty += KEY_SIZE(k);
+                        if (d)
+                                d->sectors_dirty_gc += KEY_SIZE(k);
+                }
+        }
+
+        for (t = b->sets; t <= &b->sets[b->nsets]; t++)
+                btree_bug_on(t->size &&
+                             bset_written(b, t) &&
+                             bkey_cmp(&b->key, &t->end) < 0,
+                             b, "found short btree key in gc");
+
+        return stale;
+}
+
+static struct btree *btree_gc_alloc(struct btree *b, struct bkey *k,
+                                    struct btree_op *op)
+{
+        /*
+         * We block priorities from being written for the duration of garbage
+         * collection, so we can't sleep in btree_alloc() ->
+         * bch_bucket_alloc_set(), or we'd risk deadlock - so we don't pass it
+         * our closure.
+         */
+        struct btree *n = btree_node_alloc_replacement(b, NULL);
+
+        if (!IS_ERR_OR_NULL(n)) {
+                swap(b, n);
+
+                memcpy(k->ptr, b->key.ptr,
+                       sizeof(uint64_t) * KEY_PTRS(&b->key));
+
+                __bkey_put(b->c, &b->key);
+                atomic_inc(&b->c->prio_blocked);
+                b->prio_blocked++;
+
+                btree_node_free(n, op);
+                up_write(&n->lock);
+        }
+
+        return b;
+}
+
+/*
+ * Leaving this at 2 until we've got incremental garbage collection done; it
+ * could be higher (and has been tested with 4) except that garbage collection
+ * could take much longer, adversely affecting latency.
+ */
+#define GC_MERGE_NODES  2U
+
+struct gc_merge_info {
+        struct btree    *b;
+        struct bkey     *k;
+        unsigned        keys;
+};
+
+static void btree_gc_coalesce(struct btree *b, struct btree_op *op,
+                              struct gc_stat *gc, struct gc_merge_info *r)
+{
+        unsigned nodes = 0, keys = 0, blocks;
+        int i;
+
+        while (nodes < GC_MERGE_NODES && r[nodes].b)
+                keys += r[nodes++].keys;
+
+        blocks = btree_default_blocks(b->c) * 2 / 3;
+
+        if (nodes < 2 ||
+            __set_blocks(b->sets[0].data, keys, b->c) > blocks * (nodes - 1))
+                return;
+
+        for (i = nodes - 1; i >= 0; --i) {
+                if (r[i].b->written)
+                        r[i].b = btree_gc_alloc(r[i].b, r[i].k, op);
+
+                if (r[i].b->written)
+                        return;
+        }
+
+        for (i = nodes - 1; i > 0; --i) {
+                struct bset *n1 = r[i].b->sets->data;
+                struct bset *n2 = r[i - 1].b->sets->data;
+                struct bkey *k, *last = NULL;
+
+                keys = 0;
+
+                if (i == 1) {
+                        /*
+                         * Last node we're not getting rid of - we're getting
+                         * rid of the node at r[0]. Have to try and fit all of
+                         * the remaining keys into this node; we can't ensure
+                         * they will always fit due to rounding and variable
+                         * length keys (shouldn't be possible in practice,
+                         * though)
+                         */
+                        if (__set_blocks(n1, n1->keys + r->keys,
+                                         b->c) > btree_blocks(r[i].b))
+                                return;
+
+                        keys = n2->keys;
+                        last = &r->b->key;
+                } else
+                        for (k = n2->start;
+                             k < end(n2);
+                             k = bkey_next(k)) {
+                                if (__set_blocks(n1, n1->keys + keys +
+                                                 bkey_u64s(k), b->c) > blocks)
+                                        break;
+
+                                last = k;
+                                keys += bkey_u64s(k);
+                        }
+
+                BUG_ON(__set_blocks(n1, n1->keys + keys,
+                                    b->c) > btree_blocks(r[i].b));
+
+                if (last) {
+                        bkey_copy_key(&r[i].b->key, last);
+                        bkey_copy_key(r[i].k, last);
+                }
+
+                memcpy(end(n1),
+                       n2->start,
+                       (void *) node(n2, keys) - (void *) n2->start);
+
+                n1->keys += keys;
+
+                memmove(n2->start,
+                        node(n2, keys),
+                        (void *) end(n2) - (void *) node(n2, keys));
+
+                n2->keys -= keys;
+
+                r[i].keys       = n1->keys;
+                r[i - 1].keys   = n2->keys;
+        }
+
+        btree_node_free(r->b, op);
+        up_write(&r->b->lock);
+
+        pr_debug("coalesced %u nodes", nodes);
+
+        gc->nodes--;
+        nodes--;
+
+        memmove(&r[0], &r[1], sizeof(struct gc_merge_info) * nodes);
+        memset(&r[nodes], 0, sizeof(struct gc_merge_info));
+}
+
+static int btree_gc_recurse(struct btree *b, struct btree_op *op,
+                            struct closure *writes, struct gc_stat *gc)
+{
+        void write(struct btree *r)
+        {
+                if (!r->written)
+                        bch_btree_write(r, true, op);
+                else if (btree_node_dirty(r)) {
+                        BUG_ON(btree_current_write(r)->owner);
+                        btree_current_write(r)->owner = writes;
+                        closure_get(writes);
+
+                        bch_btree_write(r, true, NULL);
+                }
+
+                up_write(&r->lock);
+        }
+
+        int ret = 0, stale;
+        unsigned i;
+        struct gc_merge_info r[GC_MERGE_NODES];
+
+        memset(r, 0, sizeof(r));
+
+        while ((r->k = bch_next_recurse_key(b, &b->c->gc_done))) {
+                r->b = bch_btree_node_get(b->c, r->k, b->level - 1, op);
+
+                if (IS_ERR(r->b)) {
+                        ret = PTR_ERR(r->b);
+                        break;
+                }
+
+                r->keys = 0;
+                stale = btree_gc_mark_node(r->b, &r->keys, gc);
+
+                if (!b->written &&
+                    (r->b->level || stale > 10 ||
+                     b->c->gc_always_rewrite))
+                        r->b = btree_gc_alloc(r->b, r->k, op);
+
+                if (r->b->level)
+                        ret = btree_gc_recurse(r->b, op, writes, gc);
+
+                if (ret) {
+                        write(r->b);
+                        break;
+                }
+
+                bkey_copy_key(&b->c->gc_done, r->k);
+
+                if (!b->written)
+                        btree_gc_coalesce(b, op, gc, r);
+
+                if (r[GC_MERGE_NODES - 1].b)
+                        write(r[GC_MERGE_NODES - 1].b);
+
+                memmove(&r[1], &r[0],
+                        sizeof(struct gc_merge_info) * (GC_MERGE_NODES - 1));
+
+                /* When we've got incremental GC working, we'll want to do
+                 * if (should_resched())
+                 *      return -EAGAIN;
+                 */
+                cond_resched();
+#if 0
+                if (need_resched()) {
+                        ret = -EAGAIN;
+                        break;
+                }
+#endif
+        }
+
+        for (i = 1; i < GC_MERGE_NODES && r[i].b; i++)
+                write(r[i].b);
+
+        /* Might have freed some children, must remove their keys */
+        if (!b->written)
+                bch_btree_sort(b);
+
+        return ret;
+}
+
+static int bch_btree_gc_root(struct btree *b, struct btree_op *op,
+                             struct closure *writes, struct gc_stat *gc)
+{
+        struct btree *n = NULL;
+        unsigned keys = 0;
+        int ret = 0, stale = btree_gc_mark_node(b, &keys, gc);
+
+        if (b->level || stale > 10)
+                n = btree_node_alloc_replacement(b, NULL);
+
+        if (!IS_ERR_OR_NULL(n))
+                swap(b, n);
+
+        if (b->level)
+                ret = btree_gc_recurse(b, op, writes, gc);
+
+        if (!b->written || btree_node_dirty(b)) {
+                atomic_inc(&b->c->prio_blocked);
+                b->prio_blocked++;
+                bch_btree_write(b, true, n ? op : NULL);
+        }
+
+        if (!IS_ERR_OR_NULL(n)) {
+                closure_sync(&op->cl);
+                bch_btree_set_root(b);
+                btree_node_free(n, op);
+                rw_unlock(true, b);
+        }
+
+        return ret;
+}
+
+static void btree_gc_start(struct cache_set *c)
+{
+        struct cache *ca;
+        struct bucket *b;
+        struct bcache_device **d;
+        unsigned i;
+
+        if (!c->gc_mark_valid)
+                return;
+
+        mutex_lock(&c->bucket_lock);
+
+        c->gc_mark_valid = 0;
+        c->gc_done = ZERO_KEY;
+
+        for_each_cache(ca, c, i)
+                for_each_bucket(b, ca) {
+                        b->gc_gen = b->gen;
+                        if (!atomic_read(&b->pin))
+                                SET_GC_MARK(b, GC_MARK_RECLAIMABLE);
+                }
+
+        for (d = c->devices;
+             d < c->devices + c->nr_uuids;
+             d++)
+                if (*d)
+                        (*d)->sectors_dirty_gc = 0;
+
+        mutex_unlock(&c->bucket_lock);
+}
+
+size_t bch_btree_gc_finish(struct cache_set *c)
+{
+        size_t available = 0;
+        struct bucket *b;
+        struct cache *ca;
+        struct bcache_device **d;
+        unsigned i;
+
+        mutex_lock(&c->bucket_lock);
+
+        set_gc_sectors(c);
+        c->gc_mark_valid = 1;
+        c->need_gc      = 0;
+
+        if (c->root)
+                for (i = 0; i < KEY_PTRS(&c->root->key); i++)
+                        SET_GC_MARK(PTR_BUCKET(c, &c->root->key, i),
+                                    GC_MARK_METADATA);
+
+        for (i = 0; i < KEY_PTRS(&c->uuid_bucket); i++)
+                SET_GC_MARK(PTR_BUCKET(c, &c->uuid_bucket, i),
+                            GC_MARK_METADATA);
+
+        for_each_cache(ca, c, i) {
+                uint64_t *i;
+
+                ca->invalidate_needs_gc = 0;
+
+                for (i = ca->sb.d; i < ca->sb.d + ca->sb.keys; i++)
+                        SET_GC_MARK(ca->buckets + *i, GC_MARK_METADATA);
+
+                for (i = ca->prio_buckets;
+                     i < ca->prio_buckets + prio_buckets(ca) * 2; i++)
+                        SET_GC_MARK(ca->buckets + *i, GC_MARK_METADATA);
+
+                for_each_bucket(b, ca) {
+                        b->last_gc      = b->gc_gen;
+                        c->need_gc      = max(c->need_gc, bucket_gc_gen(b));
+
+                        if (!atomic_read(&b->pin) &&
+                            GC_MARK(b) == GC_MARK_RECLAIMABLE) {
+                                available++;
+                                if (!GC_SECTORS_USED(b))
+                                        bch_bucket_add_unused(ca, b);
+                        }
+                }
+        }
+
+        for (d = c->devices;
+             d < c->devices + c->nr_uuids;
+             d++)
+                if (*d) {
+                        unsigned long last =
+                                atomic_long_read(&((*d)->sectors_dirty));
+                        long difference = (*d)->sectors_dirty_gc - last;
+
+                        pr_debug("sectors dirty off by %li", difference);
+
+                        (*d)->sectors_dirty_last += difference;
+
+                        atomic_long_set(&((*d)->sectors_dirty),
+                                        (*d)->sectors_dirty_gc);
+                }
+
+        mutex_unlock(&c->bucket_lock);
+        return available;
+}
+
+static void bch_btree_gc(struct closure *cl)
+{
+        struct cache_set *c = container_of(cl, struct cache_set, gc.cl);
+        int ret;
+        unsigned long available;
+        struct gc_stat stats;
+        struct closure writes;
+        struct btree_op op;
+
+        uint64_t start_time = local_clock();
+        trace_bcache_gc_start(c->sb.set_uuid);
+        blktrace_msg_all(c, "Starting gc");
+
+        memset(&stats, 0, sizeof(struct gc_stat));
+        closure_init_stack(&writes);
+        bch_btree_op_init_stack(&op);
+        op.lock = SHRT_MAX;
+
+        btree_gc_start(c);
+
+        ret = btree_root(gc_root, c, &op, &writes, &stats);
+        closure_sync(&op.cl);
+        closure_sync(&writes);
+
+        if (ret) {
+                blktrace_msg_all(c, "Stopped gc");
+                pr_warn("gc failed!");
+
+                continue_at(cl, bch_btree_gc, bch_gc_wq);
+        }
+
+        /* Possibly wait for new UUIDs or whatever to hit disk */
+        bch_journal_meta(c, &op.cl);
+        closure_sync(&op.cl);
+
+        available = bch_btree_gc_finish(c);
+
+        time_stats_update(&c->btree_gc_time, start_time);
+
+        stats.key_bytes *= sizeof(uint64_t);
+        stats.dirty     <<= 9;
+        stats.data      <<= 9;
+        stats.in_use    = (c->nbuckets - available) * 100 / c->nbuckets;
+        memcpy(&c->gc_stats, &stats, sizeof(struct gc_stat));
+        blktrace_msg_all(c, "Finished gc");
+
+        trace_bcache_gc_end(c->sb.set_uuid);
+        wake_up(&c->alloc_wait);
+        closure_wake_up(&c->bucket_wait);
+
+        continue_at(cl, bch_moving_gc, bch_gc_wq);
+}
+
+void bch_queue_gc(struct cache_set *c)
+{
+        closure_trylock_call(&c->gc.cl, bch_btree_gc, bch_gc_wq, &c->cl);
+}
+
+/* Initial partial gc */
+
+static int bch_btree_check_recurse(struct btree *b, struct btree_op *op,
+                                   unsigned long **seen)
+{
+        int ret;
+        unsigned i;
+        struct bkey *k;
+        struct bucket *g;
+        struct btree_iter iter;
+
+        for_each_key_filter(b, k, &iter, bch_ptr_invalid) {
+                for (i = 0; i < KEY_PTRS(k); i++) {
+                        if (!ptr_available(b->c, k, i))
+                                continue;
+
+                        g = PTR_BUCKET(b->c, k, i);
+
+                        if (!__test_and_set_bit(PTR_BUCKET_NR(b->c, k, i),
+                                                seen[PTR_DEV(k, i)]) ||
+                            !ptr_stale(b->c, k, i)) {
+                                g->gen = PTR_GEN(k, i);
+
+                                if (b->level)
+                                        g->prio = BTREE_PRIO;
+                                else if (g->prio == BTREE_PRIO)
+                                        g->prio = INITIAL_PRIO;
+                        }
+                }
+
+                btree_mark_key(b, k);
+        }
+
+        if (b->level) {
+                k = bch_next_recurse_key(b, &ZERO_KEY);
+
+                while (k) {
+                        struct bkey *p = bch_next_recurse_key(b, k);
+                        if (p)
+                                btree_node_prefetch(b->c, p, b->level - 1);
+
+                        ret = btree(check_recurse, k, b, op, seen);
+                        if (ret)
+                                return ret;
+
+                        k = p;
+                }
+        }
+
+        return 0;
+}
+
+int bch_btree_check(struct cache_set *c, struct btree_op *op)
+{
+        int ret = -ENOMEM;
+        unsigned i;
+        unsigned long *seen[MAX_CACHES_PER_SET];
+
+        memset(seen, 0, sizeof(seen));
+
+        for (i = 0; c->cache[i]; i++) {
+                size_t n = DIV_ROUND_UP(c->cache[i]->sb.nbuckets, 8);
+                seen[i] = kmalloc(n, GFP_KERNEL);
+                if (!seen[i])
+                        goto err;
+
+                /* Disables the seen array until prio_read() uses it too */
+                memset(seen[i], 0xFF, n);
+        }
+
+        ret = btree_root(check_recurse, c, op, seen);
+err:
+        for (i = 0; i < MAX_CACHES_PER_SET; i++)
+                kfree(seen[i]);
+        return ret;
+}
+
+/* Btree insertion */
+
+static void shift_keys(struct btree *b, struct bkey *where, struct bkey *insert)
+{
+        struct bset *i = b->sets[b->nsets].data;
+
+        memmove((uint64_t *) where + bkey_u64s(insert),
+                where,
+                (void *) end(i) - (void *) where);
+
+        i->keys += bkey_u64s(insert);
+        bkey_copy(where, insert);
+        bch_bset_fix_lookup_table(b, where);
+}
+
+static bool fix_overlapping_extents(struct btree *b,
+                                    struct bkey *insert,
+                                    struct btree_iter *iter,
+                                    struct btree_op *op)
+{
+        void subtract_dirty(struct bkey *k, int sectors)
+        {
+                struct bcache_device *d = b->c->devices[KEY_INODE(k)];
+
+                if (KEY_DIRTY(k) && d)
+                        atomic_long_sub(sectors, &d->sectors_dirty);
+        }
+
+        unsigned old_size, sectors_found = 0;
+
+        while (1) {
+                struct bkey *k = bch_btree_iter_next(iter);
+                if (!k ||
+                    bkey_cmp(&START_KEY(k), insert) >= 0)
+                        break;
+
+                if (bkey_cmp(k, &START_KEY(insert)) <= 0)
+                        continue;
+
+                old_size = KEY_SIZE(k);
+
+                /*
+                 * We might overlap with 0 size extents; we can't skip these
+                 * because if they're in the set we're inserting to we have to
+                 * adjust them so they don't overlap with the key we're
+                 * inserting. But we don't want to check them for BTREE_REPLACE
+                 * operations.
+                 */
+
+                if (op->type == BTREE_REPLACE &&
+                    KEY_SIZE(k)) {
+                        /*
+                         * k might have been split since we inserted/found the
+                         * key we're replacing
+                         */
+                        unsigned i;
+                        uint64_t offset = KEY_START(k) -
+                                KEY_START(&op->replace);
+
+                        /* But it must be a subset of the replace key */
+                        if (KEY_START(k) < KEY_START(&op->replace) ||
+                            KEY_OFFSET(k) > KEY_OFFSET(&op->replace))
+                                goto check_failed;
+
+                        /* We didn't find a key that we were supposed to */
+                        if (KEY_START(k) > KEY_START(insert) + sectors_found)
+                                goto check_failed;
+
+                        if (KEY_PTRS(&op->replace) != KEY_PTRS(k))
+                                goto check_failed;
+
+                        /* skip past gen */
+                        offset <<= 8;
+
+                        BUG_ON(!KEY_PTRS(&op->replace));
+
+                        for (i = 0; i < KEY_PTRS(&op->replace); i++)
+                                if (k->ptr[i] != op->replace.ptr[i] + offset)
+                                        goto check_failed;
+
+                        sectors_found = KEY_OFFSET(k) - KEY_START(insert);
+                }
+
+                if (bkey_cmp(insert, k) < 0 &&
+                    bkey_cmp(&START_KEY(insert), &START_KEY(k)) > 0) {
+                        /*
+                         * We overlapped in the middle of an existing key: that
+                         * means we have to split the old key. But we have to do
+                         * slightly different things depending on whether the
+                         * old key has been written out yet.
+                         */
+
+                        struct bkey *top;
+
+                        subtract_dirty(k, KEY_SIZE(insert));
+
+                        if (bkey_written(b, k)) {
+                                /*
+                                 * We insert a new key to cover the top of the
+                                 * old key, and the old key is modified in place
+                                 * to represent the bottom split.
+                                 *
+                                 * It's completely arbitrary whether the new key
+                                 * is the top or the bottom, but it has to match
+                                 * up with what btree_sort_fixup() does - it
+                                 * doesn't check for this kind of overlap, it
+                                 * depends on us inserting a new key for the top
+                                 * here.
+                                 */
+                                top = bch_bset_search(b, &b->sets[b->nsets],
+                                                      insert);
+                                shift_keys(b, top, k);
+                        } else {
+                                BKEY_PADDED(key) temp;
+                                bkey_copy(&temp.key, k);
+                                shift_keys(b, k, &temp.key);
+                                top = bkey_next(k);
+                        }
+
+                        bch_cut_front(insert, top);
+                        bch_cut_back(&START_KEY(insert), k);
+                        bch_bset_fix_invalidated_key(b, k);
+                        return false;
+                }
+
+                if (bkey_cmp(insert, k) < 0) {
+                        bch_cut_front(insert, k);
+                } else {
+                        if (bkey_written(b, k) &&
+                            bkey_cmp(&START_KEY(insert), &START_KEY(k)) <= 0) {
+                                /*
+                                 * Completely overwrote, so we don't have to
+                                 * invalidate the binary search tree
+                                 */
+                                bch_cut_front(k, k);
+                        } else {
+                                __bch_cut_back(&START_KEY(insert), k);
+                                bch_bset_fix_invalidated_key(b, k);
+                        }
+                }
+
+                subtract_dirty(k, old_size - KEY_SIZE(k));
+        }
+
+check_failed:
+        if (op->type == BTREE_REPLACE) {
+                if (!sectors_found) {
+                        op->insert_collision = true;
+                        return true;
+                } else if (sectors_found < KEY_SIZE(insert)) {
+                        SET_KEY_OFFSET(insert, KEY_OFFSET(insert) -
+                                       (KEY_SIZE(insert) - sectors_found));
+                        SET_KEY_SIZE(insert, sectors_found);
+                }
+        }
+
+        return false;
+}
+
+static bool btree_insert_key(struct btree *b, struct btree_op *op,
+                             struct bkey *k)
+{
+        struct bset *i = b->sets[b->nsets].data;
+        struct bkey *m, *prev;
+        const char *status = "insert";
+
+        BUG_ON(bkey_cmp(k, &b->key) > 0);
+        BUG_ON(b->level && !KEY_PTRS(k));
+        BUG_ON(!b->level && !KEY_OFFSET(k));
+
+        if (!b->level) {
+                struct btree_iter iter;
+                struct bkey search = KEY(KEY_INODE(k), KEY_START(k), 0);
+
+                /*
+                 * bset_search() returns the first key that is strictly greater
+                 * than the search key - but for back merging, we want to find
+                 * the first key that is greater than or equal to KEY_START(k) -
+                 * unless KEY_START(k) is 0.
+                 */
+                if (KEY_OFFSET(&search))
+                        SET_KEY_OFFSET(&search, KEY_OFFSET(&search) - 1);
+
+                prev = NULL;
+                m = bch_btree_iter_init(b, &iter, &search);
+
+                if (fix_overlapping_extents(b, k, &iter, op))
+                        return false;
+
+                while (m != end(i) &&
+                       bkey_cmp(k, &START_KEY(m)) > 0)
+                        prev = m, m = bkey_next(m);
+
+                if (key_merging_disabled(b->c))
+                        goto insert;
+
+                /* prev is in the tree, if we merge we're done */
+                status = "back merging";
+                if (prev &&
+                    bch_bkey_try_merge(b, prev, k))
+                        goto merged;
+
+                status = "overwrote front";
+                if (m != end(i) &&
+                    KEY_PTRS(m) == KEY_PTRS(k) && !KEY_SIZE(m))
+                        goto copy;
+
+                status = "front merge";
+                if (m != end(i) &&
+                    bch_bkey_try_merge(b, k, m))
+                        goto copy;
+        } else
+                m = bch_bset_search(b, &b->sets[b->nsets], k);
+
+insert: shift_keys(b, m, k);
+copy:   bkey_copy(m, k);
+merged:
+        bch_check_keys(b, "%s for %s at %s: %s", status,
+                       op_type(op), pbtree(b), pkey(k));
+        bch_check_key_order_msg(b, i, "%s for %s at %s: %s", status,
+                                op_type(op), pbtree(b), pkey(k));
+
+        if (b->level && !KEY_OFFSET(k))
+                b->prio_blocked++;
+
+        pr_debug("%s for %s at %s: %s", status,
+                 op_type(op), pbtree(b), pkey(k));
+
+        return true;
+}
+
+bool bch_btree_insert_keys(struct btree *b, struct btree_op *op)
+{
+        bool ret = false;
+        struct bkey *k;
+        unsigned oldsize = bch_count_data(b);
+
+        while ((k = bch_keylist_pop(&op->keys))) {
+                bkey_put(b->c, k, b->level);
+                ret |= btree_insert_key(b, op, k);
+        }
+
+        BUG_ON(bch_count_data(b) < oldsize);
+        return ret;
+}
+
+bool bch_btree_insert_check_key(struct btree *b, struct btree_op *op,
+                                   struct bio *bio)
+{
+        bool ret = false;
+        uint64_t btree_ptr = b->key.ptr[0];
+        unsigned long seq = b->seq;
+        BKEY_PADDED(k) tmp;
+
+        rw_unlock(false, b);
+        rw_lock(true, b, b->level);
+
+        if (b->key.ptr[0] != btree_ptr ||
+            b->seq != seq + 1 ||
+            should_split(b))
+                goto out;
+
+        op->replace = KEY(op->inode, bio_end(bio), bio_sectors(bio));
+
+        SET_KEY_PTRS(&op->replace, 1);
+        get_random_bytes(&op->replace.ptr[0], sizeof(uint64_t));
+
+        SET_PTR_DEV(&op->replace, 0, PTR_CHECK_DEV);
+
+        bkey_copy(&tmp.k, &op->replace);
+
+        BUG_ON(op->type != BTREE_INSERT);
+        BUG_ON(!btree_insert_key(b, op, &tmp.k));
+        bch_btree_write(b, false, NULL);
+        ret = true;
+out:
+        downgrade_write(&b->lock);
+        return ret;
+}
+
+static int btree_split(struct btree *b, struct btree_op *op)
+{
+        bool split, root = b == b->c->root;
+        struct btree *n1, *n2 = NULL, *n3 = NULL;
+        uint64_t start_time = local_clock();
+
+        if (b->level)
+                set_closure_blocking(&op->cl);
+
+        n1 = btree_node_alloc_replacement(b, &op->cl);
+        if (IS_ERR(n1))
+                goto err;
+
+        split = set_blocks(n1->sets[0].data, n1->c) > (btree_blocks(b) * 4) / 5;
+
+        pr_debug("%ssplitting at %s keys %i", split ? "" : "not ",
+                 pbtree(b), n1->sets[0].data->keys);
+
+        if (split) {
+                unsigned keys = 0;
+
+                n2 = bch_btree_node_alloc(b->c, b->level, &op->cl);
+                if (IS_ERR(n2))
+                        goto err_free1;
+
+                if (root) {
+                        n3 = bch_btree_node_alloc(b->c, b->level + 1, &op->cl);
+                        if (IS_ERR(n3))
+                                goto err_free2;
+                }
+
+                bch_btree_insert_keys(n1, op);
+
+                /* Has to be a linear search because we don't have an auxiliary
+                 * search tree yet
+                 */
+
+                while (keys < (n1->sets[0].data->keys * 3) / 5)
+                        keys += bkey_u64s(node(n1->sets[0].data, keys));
+
+                bkey_copy_key(&n1->key, node(n1->sets[0].data, keys));
+                keys += bkey_u64s(node(n1->sets[0].data, keys));
+
+                n2->sets[0].data->keys = n1->sets[0].data->keys - keys;
+                n1->sets[0].data->keys = keys;
+
+                memcpy(n2->sets[0].data->start,
+                       end(n1->sets[0].data),
+                       n2->sets[0].data->keys * sizeof(uint64_t));
+
+                bkey_copy_key(&n2->key, &b->key);
+
+                bch_keylist_add(&op->keys, &n2->key);
+                bch_btree_write(n2, true, op);
+                rw_unlock(true, n2);
+        } else
+                bch_btree_insert_keys(n1, op);
+
+        bch_keylist_add(&op->keys, &n1->key);
+        bch_btree_write(n1, true, op);
+
+        if (n3) {
+                bkey_copy_key(&n3->key, &MAX_KEY);
+                bch_btree_insert_keys(n3, op);
+                bch_btree_write(n3, true, op);
+
+                closure_sync(&op->cl);
+                bch_btree_set_root(n3);
+                rw_unlock(true, n3);
+        } else if (root) {
+                op->keys.top = op->keys.bottom;
+                closure_sync(&op->cl);
+                bch_btree_set_root(n1);
+        } else {
+                unsigned i;
+
+                bkey_copy(op->keys.top, &b->key);
+                bkey_copy_key(op->keys.top, &ZERO_KEY);
+
+                for (i = 0; i < KEY_PTRS(&b->key); i++) {
+                        uint8_t g = PTR_BUCKET(b->c, &b->key, i)->gen + 1;
+
+                        SET_PTR_GEN(op->keys.top, i, g);
+                }
+
+                bch_keylist_push(&op->keys);
+                closure_sync(&op->cl);
+                atomic_inc(&b->c->prio_blocked);
+        }
+
+        rw_unlock(true, n1);
+        btree_node_free(b, op);
+
+        time_stats_update(&b->c->btree_split_time, start_time);
+
+        return 0;
+err_free2:
+        __bkey_put(n2->c, &n2->key);
+        btree_node_free(n2, op);
+        rw_unlock(true, n2);
+err_free1:
+        __bkey_put(n1->c, &n1->key);
+        btree_node_free(n1, op);
+        rw_unlock(true, n1);
+err:
+        if (n3 == ERR_PTR(-EAGAIN) ||
+            n2 == ERR_PTR(-EAGAIN) ||
+            n1 == ERR_PTR(-EAGAIN))
+                return -EAGAIN;
+
+        pr_warn("couldn't split");
+        return -ENOMEM;
+}
+
+static int bch_btree_insert_recurse(struct btree *b, struct btree_op *op,
+                                    struct keylist *stack_keys)
+{
+        if (b->level) {
+                int ret;
+                struct bkey *insert = op->keys.bottom;
+                struct bkey *k = bch_next_recurse_key(b, &START_KEY(insert));
+
+                if (!k) {
+                        btree_bug(b, "no key to recurse on at level %i/%i",
+                                  b->level, b->c->root->level);
+
+                        op->keys.top = op->keys.bottom;
+                        return -EIO;
+                }
+
+                if (bkey_cmp(insert, k) > 0) {
+                        unsigned i;
+
+                        if (op->type == BTREE_REPLACE) {
+                                __bkey_put(b->c, insert);
+                                op->keys.top = op->keys.bottom;
+                                op->insert_collision = true;
+                                return 0;
+                        }
+
+                        for (i = 0; i < KEY_PTRS(insert); i++)
+                                atomic_inc(&PTR_BUCKET(b->c, insert, i)->pin);
+
+                        bkey_copy(stack_keys->top, insert);
+
+                        bch_cut_back(k, insert);
+                        bch_cut_front(k, stack_keys->top);
+
+                        bch_keylist_push(stack_keys);
+                }
+
+                ret = btree(insert_recurse, k, b, op, stack_keys);
+                if (ret)
+                        return ret;
+        }
+
+        if (!bch_keylist_empty(&op->keys)) {
+                if (should_split(b)) {
+                        if (op->lock <= b->c->root->level) {
+                                BUG_ON(b->level);
+                                op->lock = b->c->root->level + 1;
+                                return -EINTR;
+                        }
+                        return btree_split(b, op);
+                }
+
+                BUG_ON(write_block(b) != b->sets[b->nsets].data);
+
+                if (bch_btree_insert_keys(b, op))
+                        bch_btree_write(b, false, op);
+        }
+
+        return 0;
+}
+
+int bch_btree_insert(struct btree_op *op, struct cache_set *c)
+{
+        int ret = 0;
+        struct keylist stack_keys;
+
+        /*
+         * Don't want to block with the btree locked unless we have to,
+         * otherwise we get deadlocks with try_harder and between split/gc
+         */
+        clear_closure_blocking(&op->cl);
+
+        BUG_ON(bch_keylist_empty(&op->keys));
+        bch_keylist_copy(&stack_keys, &op->keys);
+        bch_keylist_init(&op->keys);
+
+        while (!bch_keylist_empty(&stack_keys) ||
+               !bch_keylist_empty(&op->keys)) {
+                if (bch_keylist_empty(&op->keys)) {
+                        bch_keylist_add(&op->keys,
+                                        bch_keylist_pop(&stack_keys));
+                        op->lock = 0;
+                }
+
+                ret = btree_root(insert_recurse, c, op, &stack_keys);
+
+                if (ret == -EAGAIN) {
+                        ret = 0;
+                        closure_sync(&op->cl);
+                } else if (ret) {
+                        struct bkey *k;
+
+                        pr_err("error %i trying to insert key for %s",
+                               ret, op_type(op));
+
+                        while ((k = bch_keylist_pop(&stack_keys) ?:
+                                    bch_keylist_pop(&op->keys)))
+                                bkey_put(c, k, 0);
+                }
+        }
+
+        bch_keylist_free(&stack_keys);
+
+        if (op->journal)
+                atomic_dec_bug(op->journal);
+        op->journal = NULL;
+        return ret;
+}
+
+void bch_btree_set_root(struct btree *b)
+{
+        unsigned i;
+
+        BUG_ON(!b->written);
+
+        for (i = 0; i < KEY_PTRS(&b->key); i++)
+                BUG_ON(PTR_BUCKET(b->c, &b->key, i)->prio != BTREE_PRIO);
+
+        mutex_lock(&b->c->bucket_lock);
+        list_del_init(&b->list);
+        mutex_unlock(&b->c->bucket_lock);
+
+        b->c->root = b;
+        __bkey_put(b->c, &b->key);
+
+        bch_journal_meta(b->c, NULL);
+        pr_debug("%s for %pf", pbtree(b), __builtin_return_address(0));
+}
+
+/* Cache lookup */
+
+static int submit_partial_cache_miss(struct btree *b, struct btree_op *op,
+                                     struct bkey *k)
+{
+        struct search *s = container_of(op, struct search, op);
+        struct bio *bio = &s->bio.bio;
+        int ret = 0;
+
+        while (!ret &&
+               !op->lookup_done) {
+                unsigned sectors = INT_MAX;
+
+                if (KEY_INODE(k) == op->inode) {
+                        if (KEY_START(k) <= bio->bi_sector)
+                                break;
+
+                        sectors = min_t(uint64_t, sectors,
+                                        KEY_START(k) - bio->bi_sector);
+                }
+
+                ret = s->d->cache_miss(b, s, bio, sectors);
+        }
+
+        return ret;
+}
+
+/*
+ * Read from a single key, handling the initial cache miss if the key starts in
+ * the middle of the bio
+ */
+static int submit_partial_cache_hit(struct btree *b, struct btree_op *op,
+                                    struct bkey *k)
+{
+        struct search *s = container_of(op, struct search, op);
+        struct bio *bio = &s->bio.bio;
+        unsigned ptr;
+        struct bio *n;
+
+        int ret = submit_partial_cache_miss(b, op, k);
+        if (ret || op->lookup_done)
+                return ret;
+
+        /* XXX: figure out best pointer - for multiple cache devices */
+        ptr = 0;
+
+        PTR_BUCKET(b->c, k, ptr)->prio = INITIAL_PRIO;
+
+        while (!op->lookup_done &&
+               KEY_INODE(k) == op->inode &&
+               bio->bi_sector < KEY_OFFSET(k)) {
+                struct bkey *bio_key;
+                sector_t sector = PTR_OFFSET(k, ptr) +
+                        (bio->bi_sector - KEY_START(k));
+                unsigned sectors = min_t(uint64_t, INT_MAX,
+                                         KEY_OFFSET(k) - bio->bi_sector);
+
+                n = bch_bio_split(bio, sectors, GFP_NOIO, s->d->bio_split);
+                if (!n)
+                        return -EAGAIN;
+
+                if (n == bio)
+                        op->lookup_done = true;
+
+                bio_key = &container_of(n, struct bbio, bio)->key;
+
+                /*
+                 * The bucket we're reading from might be reused while our bio
+                 * is in flight, and we could then end up reading the wrong
+                 * data.
+                 *
+                 * We guard against this by checking (in cache_read_endio()) if
+                 * the pointer is stale again; if so, we treat it as an error
+                 * and reread from the backing device (but we don't pass that
+                 * error up anywhere).
+                 */
+
+                bch_bkey_copy_single_ptr(bio_key, k, ptr);
+                SET_PTR_OFFSET(bio_key, 0, sector);
+
+                n->bi_end_io    = bch_cache_read_endio;
+                n->bi_private   = &s->cl;
+
+                trace_bcache_cache_hit(n);
+                __bch_submit_bbio(n, b->c);
+        }
+
+        return 0;
+}
+
+int bch_btree_search_recurse(struct btree *b, struct btree_op *op)
+{
+        struct search *s = container_of(op, struct search, op);
+        struct bio *bio = &s->bio.bio;
+
+        int ret = 0;
+        struct bkey *k;
+        struct btree_iter iter;
+        bch_btree_iter_init(b, &iter, &KEY(op->inode, bio->bi_sector, 0));
+
+        pr_debug("at %s searching for %u:%llu", pbtree(b), op->inode,
+                 (uint64_t) bio->bi_sector);
+
+        do {
+                k = bch_btree_iter_next_filter(&iter, b, bch_ptr_bad);
+                if (!k) {
+                        /*
+                         * b->key would be exactly what we want, except that
+                         * pointers to btree nodes have nonzero size - we
+                         * wouldn't go far enough
+                         */
+
+                        ret = submit_partial_cache_miss(b, op,
+                                        &KEY(KEY_INODE(&b->key),
+                                             KEY_OFFSET(&b->key), 0));
+                        break;
+                }
+
+                ret = b->level
+                        ? btree(search_recurse, k, b, op)
+                        : submit_partial_cache_hit(b, op, k);
+        } while (!ret &&
+                 !op->lookup_done);
+
+        return ret;
+}
+
+/* Keybuf code */
+
+static inline int keybuf_cmp(struct keybuf_key *l, struct keybuf_key *r)
+{
+        /* Overlapping keys compare equal */
+        if (bkey_cmp(&l->key, &START_KEY(&r->key)) <= 0)
+                return -1;
+        if (bkey_cmp(&START_KEY(&l->key), &r->key) >= 0)
+                return 1;
+        return 0;
+}
+
+static inline int keybuf_nonoverlapping_cmp(struct keybuf_key *l,
+                                            struct keybuf_key *r)
+{
+        return clamp_t(int64_t, bkey_cmp(&l->key, &r->key), -1, 1);
+}
+
+static int bch_btree_refill_keybuf(struct btree *b, struct btree_op *op,
+                                   struct keybuf *buf, struct bkey *end)
+{
+        struct btree_iter iter;
+        bch_btree_iter_init(b, &iter, &buf->last_scanned);
+
+        while (!array_freelist_empty(&buf->freelist)) {
+                struct bkey *k = bch_btree_iter_next_filter(&iter, b,
+                                                            bch_ptr_bad);
+
+                if (!b->level) {
+                        if (!k) {
+                                buf->last_scanned = b->key;
+                                break;
+                        }
+
+                        buf->last_scanned = *k;
+                        if (bkey_cmp(&buf->last_scanned, end) >= 0)
+                                break;
+
+                        if (buf->key_predicate(buf, k)) {
+                                struct keybuf_key *w;
+
+                                pr_debug("%s", pkey(k));
+
+                                spin_lock(&buf->lock);
+
+                                w = array_alloc(&buf->freelist);
+
+                                w->private = NULL;
+                                bkey_copy(&w->key, k);
+
+                                if (RB_INSERT(&buf->keys, w, node, keybuf_cmp))
+                                        array_free(&buf->freelist, w);
+
+                                spin_unlock(&buf->lock);
+                        }
+                } else {
+                        if (!k)
+                                break;
+
+                        btree(refill_keybuf, k, b, op, buf, end);
+                        /*
+                         * Might get an error here, but can't really do anything
+                         * and it'll get logged elsewhere. Just read what we
+                         * can.
+                         */
+
+                        if (bkey_cmp(&buf->last_scanned, end) >= 0)
+                                break;
+
+                        cond_resched();
+                }
+        }
+
+        return 0;
+}
+
+void bch_refill_keybuf(struct cache_set *c, struct keybuf *buf,
+                          struct bkey *end)
+{
+        struct bkey start = buf->last_scanned;
+        struct btree_op op;
+        bch_btree_op_init_stack(&op);
+
+        cond_resched();
+
+        btree_root(refill_keybuf, c, &op, buf, end);
+        closure_sync(&op.cl);
+
+        pr_debug("found %s keys from %llu:%llu to %llu:%llu",
+                 RB_EMPTY_ROOT(&buf->keys) ? "no" :
+                 array_freelist_empty(&buf->freelist) ? "some" : "a few",
+                 KEY_INODE(&start), KEY_OFFSET(&start),
+                 KEY_INODE(&buf->last_scanned), KEY_OFFSET(&buf->last_scanned));
+
+        spin_lock(&buf->lock);
+
+        if (!RB_EMPTY_ROOT(&buf->keys)) {
+                struct keybuf_key *w;
+                w = RB_FIRST(&buf->keys, struct keybuf_key, node);
+                buf->start      = START_KEY(&w->key);
+
+                w = RB_LAST(&buf->keys, struct keybuf_key, node);
+                buf->end        = w->key;
+        } else {
+                buf->start      = MAX_KEY;
+                buf->end        = MAX_KEY;
+        }
+
+        spin_unlock(&buf->lock);
+}
+
+static void __bch_keybuf_del(struct keybuf *buf, struct keybuf_key *w)
+{
+        rb_erase(&w->node, &buf->keys);
+        array_free(&buf->freelist, w);
+}
+
+void bch_keybuf_del(struct keybuf *buf, struct keybuf_key *w)
+{
+        spin_lock(&buf->lock);
+        __bch_keybuf_del(buf, w);
+        spin_unlock(&buf->lock);
+}
+
+bool bch_keybuf_check_overlapping(struct keybuf *buf, struct bkey *start,
+                                  struct bkey *end)
+{
+        bool ret = false;
+        struct keybuf_key *p, *w, s;
+        s.key = *start;
+
+        if (bkey_cmp(end, &buf->start) <= 0 ||
+            bkey_cmp(start, &buf->end) >= 0)
+                return false;
+
+        spin_lock(&buf->lock);
+        w = RB_GREATER(&buf->keys, s, node, keybuf_nonoverlapping_cmp);
+
+        while (w && bkey_cmp(&START_KEY(&w->key), end) < 0) {
+                p = w;
+                w = RB_NEXT(w, node);
+
+                if (p->private)
+                        ret = true;
+                else
+                        __bch_keybuf_del(buf, p);
+        }
+
+        spin_unlock(&buf->lock);
+        return ret;
+}
+
+struct keybuf_key *bch_keybuf_next(struct keybuf *buf)
+{
+        struct keybuf_key *w;
+        spin_lock(&buf->lock);
+
+        w = RB_FIRST(&buf->keys, struct keybuf_key, node);
+
+        while (w && w->private)
+                w = RB_NEXT(w, node);
+
+        if (w)
+                w->private = ERR_PTR(-EINTR);
+
+        spin_unlock(&buf->lock);
+        return w;
+}
+
+struct keybuf_key *bch_keybuf_next_rescan(struct cache_set *c,
+                                             struct keybuf *buf,
+                                             struct bkey *end)
+{
+        struct keybuf_key *ret;
+
+        while (1) {
+                ret = bch_keybuf_next(buf);
+                if (ret)
+                        break;
+
+                if (bkey_cmp(&buf->last_scanned, end) >= 0) {
+                        pr_debug("scan finished");
+                        break;
+                }
+
+                bch_refill_keybuf(c, buf, end);
+        }
+
+        return ret;
+}
+
+void bch_keybuf_init(struct keybuf *buf, keybuf_pred_fn *fn)
+{
+        buf->key_predicate      = fn;
+        buf->last_scanned       = MAX_KEY;
+        buf->keys               = RB_ROOT;
+
+        spin_lock_init(&buf->lock);
+        array_allocator_init(&buf->freelist);
+}
+
+void bch_btree_exit(void)
+{
+        if (btree_io_wq)
+                destroy_workqueue(btree_io_wq);
+        if (bch_gc_wq)
+                destroy_workqueue(bch_gc_wq);
+}
+
+int __init bch_btree_init(void)
+{
+        if (!(bch_gc_wq = create_singlethread_workqueue("bch_btree_gc")) ||
+            !(btree_io_wq = create_singlethread_workqueue("bch_btree_io")))
+                return -ENOMEM;
+
+        return 0;
+}
diff --git a/drivers/md/bcache/btree.h b/drivers/md/bcache/btree.h
new file mode 100644
index 000000000000..af4a7092a28c
--- /dev/null
+++ b/drivers/md/bcache/btree.h
@@ -0,0 +1,405 @@
+#ifndef _BCACHE_BTREE_H
+#define _BCACHE_BTREE_H
+
+/*
+ * THE BTREE:
+ *
+ * At a high level, bcache's btree is relatively standard b+ tree. All keys and
+ * pointers are in the leaves; interior nodes only have pointers to the child
+ * nodes.
+ *
+ * In the interior nodes, a struct bkey always points to a child btree node, and
+ * the key is the highest key in the child node - except that the highest key in
+ * an interior node is always MAX_KEY. The size field refers to the size on disk
+ * of the child node - this would allow us to have variable sized btree nodes
+ * (handy for keeping the depth of the btree 1 by expanding just the root).
+ *
+ * Btree nodes are themselves log structured, but this is hidden fairly
+ * thoroughly. Btree nodes on disk will in practice have extents that overlap
+ * (because they were written at different times), but in memory we never have
+ * overlapping extents - when we read in a btree node from disk, the first thing
+ * we do is resort all the sets of keys with a mergesort, and in the same pass
+ * we check for overlapping extents and adjust them appropriately.
+ *
+ * struct btree_op is a central interface to the btree code. It's used for
+ * specifying read vs. write locking, and the embedded closure is used for
+ * waiting on IO or reserve memory.
+ *
+ * BTREE CACHE:
+ *
+ * Btree nodes are cached in memory; traversing the btree might require reading
+ * in btree nodes which is handled mostly transparently.
+ *
+ * bch_btree_node_get() looks up a btree node in the cache and reads it in from
+ * disk if necessary. This function is almost never called directly though - the
+ * btree() macro is used to get a btree node, call some function on it, and
+ * unlock the node after the function returns.
+ *
+ * The root is special cased - it's taken out of the cache's lru (thus pinning
+ * it in memory), so we can find the root of the btree by just dereferencing a
+ * pointer instead of looking it up in the cache. This makes locking a bit
+ * tricky, since the root pointer is protected by the lock in the btree node it
+ * points to - the btree_root() macro handles this.
+ *
+ * In various places we must be able to allocate memory for multiple btree nodes
+ * in order to make forward progress. To do this we use the btree cache itself
+ * as a reserve; if __get_free_pages() fails, we'll find a node in the btree
+ * cache we can reuse. We can't allow more than one thread to be doing this at a
+ * time, so there's a lock, implemented by a pointer to the btree_op closure -
+ * this allows the btree_root() macro to implicitly release this lock.
+ *
+ * BTREE IO:
+ *
+ * Btree nodes never have to be explicitly read in; bch_btree_node_get() handles
+ * this.
+ *
+ * For writing, we have two btree_write structs embeddded in struct btree - one
+ * write in flight, and one being set up, and we toggle between them.
+ *
+ * Writing is done with a single function -  bch_btree_write() really serves two
+ * different purposes and should be broken up into two different functions. When
+ * passing now = false, it merely indicates that the node is now dirty - calling
+ * it ensures that the dirty keys will be written at some point in the future.
+ *
+ * When passing now = true, bch_btree_write() causes a write to happen
+ * "immediately" (if there was already a write in flight, it'll cause the write
+ * to happen as soon as the previous write completes). It returns immediately
+ * though - but it takes a refcount on the closure in struct btree_op you passed
+ * to it, so a closure_sync() later can be used to wait for the write to
+ * complete.
+ *
+ * This is handy because btree_split() and garbage collection can issue writes
+ * in parallel, reducing the amount of time they have to hold write locks.
+ *
+ * LOCKING:
+ *
+ * When traversing the btree, we may need write locks starting at some level -
+ * inserting a key into the btree will typically only require a write lock on
+ * the leaf node.
+ *
+ * This is specified with the lock field in struct btree_op; lock = 0 means we
+ * take write locks at level <= 0, i.e. only leaf nodes. bch_btree_node_get()
+ * checks this field and returns the node with the appropriate lock held.
+ *
+ * If, after traversing the btree, the insertion code discovers it has to split
+ * then it must restart from the root and take new locks - to do this it changes
+ * the lock field and returns -EINTR, which causes the btree_root() macro to
+ * loop.
+ *
+ * Handling cache misses require a different mechanism for upgrading to a write
+ * lock. We do cache lookups with only a read lock held, but if we get a cache
+ * miss and we wish to insert this data into the cache, we have to insert a
+ * placeholder key to detect races - otherwise, we could race with a write and
+ * overwrite the data that was just written to the cache with stale data from
+ * the backing device.
+ *
+ * For this we use a sequence number that write locks and unlocks increment - to
+ * insert the check key it unlocks the btree node and then takes a write lock,
+ * and fails if the sequence number doesn't match.
+ */
+
+#include "bset.h"
+#include "debug.h"
+
+struct btree_write {
+        struct closure          *owner;
+        atomic_t                *journal;
+
+        /* If btree_split() frees a btree node, it writes a new pointer to that
+         * btree node indicating it was freed; it takes a refcount on
+         * c->prio_blocked because we can't write the gens until the new
+         * pointer is on disk. This allows btree_write_endio() to release the
+         * refcount that btree_split() took.
+         */
+        int                     prio_blocked;
+};
+
+struct btree {
+        /* Hottest entries first */
+        struct hlist_node       hash;
+
+        /* Key/pointer for this btree node */
+        BKEY_PADDED(key);
+
+        /* Single bit - set when accessed, cleared by shrinker */
+        unsigned long           accessed;
+        unsigned long           seq;
+        struct rw_semaphore     lock;
+        struct cache_set        *c;
+
+        unsigned long           flags;
+        uint16_t                written;        /* would be nice to kill */
+        uint8_t                 level;
+        uint8_t                 nsets;
+        uint8_t                 page_order;
+
+        /*
+         * Set of sorted keys - the real btree node - plus a binary search tree
+         *
+         * sets[0] is special; set[0]->tree, set[0]->prev and set[0]->data point
+         * to the memory we have allocated for this btree node. Additionally,
+         * set[0]->data points to the entire btree node as it exists on disk.
+         */
+        struct bset_tree        sets[MAX_BSETS];
+
+        /* Used to refcount bio splits, also protects b->bio */
+        struct closure_with_waitlist    io;
+
+        /* Gets transferred to w->prio_blocked - see the comment there */
+        int                     prio_blocked;
+
+        struct list_head        list;
+        struct delayed_work     work;
+
+        uint64_t                io_start_time;
+        struct btree_write      writes[2];
+        struct bio              *bio;
+};
+
+#define BTREE_FLAG(flag)                                                \
+static inline bool btree_node_ ## flag(struct btree *b)                 \
+{       return test_bit(BTREE_NODE_ ## flag, &b->flags); }              \
+                                                                        \
+static inline void set_btree_node_ ## flag(struct btree *b)             \
+{       set_bit(BTREE_NODE_ ## flag, &b->flags); }                      \
+
+enum btree_flags {
+        BTREE_NODE_read_done,
+        BTREE_NODE_io_error,
+        BTREE_NODE_dirty,
+        BTREE_NODE_write_idx,
+};
+
+BTREE_FLAG(read_done);
+BTREE_FLAG(io_error);
+BTREE_FLAG(dirty);
+BTREE_FLAG(write_idx);
+
+static inline struct btree_write *btree_current_write(struct btree *b)
+{
+        return b->writes + btree_node_write_idx(b);
+}
+
+static inline struct btree_write *btree_prev_write(struct btree *b)
+{
+        return b->writes + (btree_node_write_idx(b) ^ 1);
+}
+
+static inline unsigned bset_offset(struct btree *b, struct bset *i)
+{
+        return (((size_t) i) - ((size_t) b->sets->data)) >> 9;
+}
+
+static inline struct bset *write_block(struct btree *b)
+{
+        return ((void *) b->sets[0].data) + b->written * block_bytes(b->c);
+}
+
+static inline bool bset_written(struct btree *b, struct bset_tree *t)
+{
+        return t->data < write_block(b);
+}
+
+static inline bool bkey_written(struct btree *b, struct bkey *k)
+{
+        return k < write_block(b)->start;
+}
+
+static inline void set_gc_sectors(struct cache_set *c)
+{
+        atomic_set(&c->sectors_to_gc, c->sb.bucket_size * c->nbuckets / 8);
+}
+
+static inline bool bch_ptr_invalid(struct btree *b, const struct bkey *k)
+{
+        return __bch_ptr_invalid(b->c, b->level, k);
+}
+
+static inline struct bkey *bch_btree_iter_init(struct btree *b,
+                                               struct btree_iter *iter,
+                                               struct bkey *search)
+{
+        return __bch_btree_iter_init(b, iter, search, b->sets);
+}
+
+/* Looping macros */
+
+#define for_each_cached_btree(b, c, iter)                               \
+        for (iter = 0;                                                  \
+             iter < ARRAY_SIZE((c)->bucket_hash);                       \
+             iter++)                                                    \
+                hlist_for_each_entry_rcu((b), (c)->bucket_hash + iter, hash)
+
+#define for_each_key_filter(b, k, iter, filter)                         \
+        for (bch_btree_iter_init((b), (iter), NULL);                    \
+             ((k) = bch_btree_iter_next_filter((iter), b, filter));)
+
+#define for_each_key(b, k, iter)                                        \
+        for (bch_btree_iter_init((b), (iter), NULL);                    \
+             ((k) = bch_btree_iter_next(iter));)
+
+/* Recursing down the btree */
+
+struct btree_op {
+        struct closure          cl;
+        struct cache_set        *c;
+
+        /* Journal entry we have a refcount on */
+        atomic_t                *journal;
+
+        /* Bio to be inserted into the cache */
+        struct bio              *cache_bio;
+
+        unsigned                inode;
+
+        uint16_t                write_prio;
+
+        /* Btree level at which we start taking write locks */
+        short                   lock;
+
+        /* Btree insertion type */
+        enum {
+                BTREE_INSERT,
+                BTREE_REPLACE
+        } type:8;
+
+        unsigned                csum:1;
+        unsigned                skip:1;
+        unsigned                flush_journal:1;
+
+        unsigned                insert_data_done:1;
+        unsigned                lookup_done:1;
+        unsigned                insert_collision:1;
+
+        /* Anything after this point won't get zeroed in do_bio_hook() */
+
+        /* Keys to be inserted */
+        struct keylist          keys;
+        BKEY_PADDED(replace);
+};
+
+void bch_btree_op_init_stack(struct btree_op *);
+
+static inline void rw_lock(bool w, struct btree *b, int level)
+{
+        w ? down_write_nested(&b->lock, level + 1)
+          : down_read_nested(&b->lock, level + 1);
+        if (w)
+                b->seq++;
+}
+
+static inline void rw_unlock(bool w, struct btree *b)
+{
+#ifdef CONFIG_BCACHE_EDEBUG
+        unsigned i;
+
+        if (w &&
+            b->key.ptr[0] &&
+            btree_node_read_done(b))
+                for (i = 0; i <= b->nsets; i++)
+                        bch_check_key_order(b, b->sets[i].data);
+#endif
+
+        if (w)
+                b->seq++;
+        (w ? up_write : up_read)(&b->lock);
+}
+
+#define insert_lock(s, b)       ((b)->level <= (s)->lock)
+
+/*
+ * These macros are for recursing down the btree - they handle the details of
+ * locking and looking up nodes in the cache for you. They're best treated as
+ * mere syntax when reading code that uses them.
+ *
+ * op->lock determines whether we take a read or a write lock at a given depth.
+ * If you've got a read lock and find that you need a write lock (i.e. you're
+ * going to have to split), set op->lock and return -EINTR; btree_root() will
+ * call you again and you'll have the correct lock.
+ */
+
+/**
+ * btree - recurse down the btree on a specified key
+ * @fn:         function to call, which will be passed the child node
+ * @key:        key to recurse on
+ * @b:          parent btree node
+ * @op:         pointer to struct btree_op
+ */
+#define btree(fn, key, b, op, ...)                                      \
+({                                                                      \
+        int _r, l = (b)->level - 1;                                     \
+        bool _w = l <= (op)->lock;                                      \
+        struct btree *_b = bch_btree_node_get((b)->c, key, l, op);      \
+        if (!IS_ERR(_b)) {                                              \
+                _r = bch_btree_ ## fn(_b, op, ##__VA_ARGS__);           \
+                rw_unlock(_w, _b);                                      \
+        } else                                                          \
+                _r = PTR_ERR(_b);                                       \
+        _r;                                                             \
+})
+
+/**
+ * btree_root - call a function on the root of the btree
+ * @fn:         function to call, which will be passed the child node
+ * @c:          cache set
+ * @op:         pointer to struct btree_op
+ */
+#define btree_root(fn, c, op, ...)                                      \
+({                                                                      \
+        int _r = -EINTR;                                                \
+        do {                                                            \
+                struct btree *_b = (c)->root;                           \
+                bool _w = insert_lock(op, _b);                          \
+                rw_lock(_w, _b, _b->level);                             \
+                if (_b == (c)->root &&                                  \
+                    _w == insert_lock(op, _b))                          \
+                        _r = bch_btree_ ## fn(_b, op, ##__VA_ARGS__);   \
+                rw_unlock(_w, _b);                                      \
+                bch_cannibalize_unlock(c, &(op)->cl);           \
+        } while (_r == -EINTR);                                         \
+                                                                        \
+        _r;                                                             \
+})
+
+static inline bool should_split(struct btree *b)
+{
+        struct bset *i = write_block(b);
+        return b->written >= btree_blocks(b) ||
+                (i->seq == b->sets[0].data->seq &&
+                 b->written + __set_blocks(i, i->keys + 15, b->c)
+                 > btree_blocks(b));
+}
+
+void bch_btree_read_done(struct closure *);
+void bch_btree_read(struct btree *);
+void bch_btree_write(struct btree *b, bool now, struct btree_op *op);
+
+void bch_cannibalize_unlock(struct cache_set *, struct closure *);
+void bch_btree_set_root(struct btree *);
+struct btree *bch_btree_node_alloc(struct cache_set *, int, struct closure *);
+struct btree *bch_btree_node_get(struct cache_set *, struct bkey *,
+                                int, struct btree_op *);
+
+bool bch_btree_insert_keys(struct btree *, struct btree_op *);
+bool bch_btree_insert_check_key(struct btree *, struct btree_op *,
+                                   struct bio *);
+int bch_btree_insert(struct btree_op *, struct cache_set *);
+
+int bch_btree_search_recurse(struct btree *, struct btree_op *);
+
+void bch_queue_gc(struct cache_set *);
+size_t bch_btree_gc_finish(struct cache_set *);
+void bch_moving_gc(struct closure *);
+int bch_btree_check(struct cache_set *, struct btree_op *);
+uint8_t __bch_btree_mark_key(struct cache_set *, int, struct bkey *);
+
+void bch_keybuf_init(struct keybuf *, keybuf_pred_fn *);
+void bch_refill_keybuf(struct cache_set *, struct keybuf *, struct bkey *);
+bool bch_keybuf_check_overlapping(struct keybuf *, struct bkey *,
+                                  struct bkey *);
+void bch_keybuf_del(struct keybuf *, struct keybuf_key *);
+struct keybuf_key *bch_keybuf_next(struct keybuf *);
+struct keybuf_key *bch_keybuf_next_rescan(struct cache_set *,
+                                          struct keybuf *, struct bkey *);
+
+#endif
diff --git a/drivers/md/bcache/closure.c b/drivers/md/bcache/closure.c
new file mode 100644
index 000000000000..d6fbec0f8484
--- /dev/null
+++ b/drivers/md/bcache/closure.c
@@ -0,0 +1,348 @@
+/*
+ * Asynchronous refcounty things
+ *
+ * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
+ * Copyright 2012 Google, Inc.
+ */
+
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/seq_file.h>
+
+#include "closure.h"
+
+void closure_queue(struct closure *cl)
+{
+        struct workqueue_struct *wq = cl->wq;
+        if (wq) {
+                INIT_WORK(&cl->work, cl->work.func);
+                BUG_ON(!queue_work(wq, &cl->work));
+        } else
+                cl->fn(cl);
+}
+EXPORT_SYMBOL_GPL(closure_queue);
+
+#define CL_FIELD(type, field)                                   \
+        case TYPE_ ## type:                                     \
+        return &container_of(cl, struct type, cl)->field
+
+static struct closure_waitlist *closure_waitlist(struct closure *cl)
+{
+        switch (cl->type) {
+                CL_FIELD(closure_with_waitlist, wait);
+                CL_FIELD(closure_with_waitlist_and_timer, wait);
+        default:
+                return NULL;
+        }
+}
+
+static struct timer_list *closure_timer(struct closure *cl)
+{
+        switch (cl->type) {
+                CL_FIELD(closure_with_timer, timer);
+                CL_FIELD(closure_with_waitlist_and_timer, timer);
+        default:
+                return NULL;
+        }
+}
+
+static inline void closure_put_after_sub(struct closure *cl, int flags)
+{
+        int r = flags & CLOSURE_REMAINING_MASK;
+
+        BUG_ON(flags & CLOSURE_GUARD_MASK);
+        BUG_ON(!r && (flags & ~(CLOSURE_DESTRUCTOR|CLOSURE_BLOCKING)));
+
+        /* Must deliver precisely one wakeup */
+        if (r == 1 && (flags & CLOSURE_SLEEPING))
+                wake_up_process(cl->task);
+
+        if (!r) {
+                if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) {
+                        /* CLOSURE_BLOCKING might be set - clear it */
+                        atomic_set(&cl->remaining,
+                                   CLOSURE_REMAINING_INITIALIZER);
+                        closure_queue(cl);
+                } else {
+                        struct closure *parent = cl->parent;
+                        struct closure_waitlist *wait = closure_waitlist(cl);
+
+                        closure_debug_destroy(cl);
+
+                        atomic_set(&cl->remaining, -1);
+
+                        if (wait)
+                                closure_wake_up(wait);
+
+                        if (cl->fn)
+                                cl->fn(cl);
+
+                        if (parent)
+                                closure_put(parent);
+                }
+        }
+}
+
+/* For clearing flags with the same atomic op as a put */
+void closure_sub(struct closure *cl, int v)
+{
+        closure_put_after_sub(cl, atomic_sub_return(v, &cl->remaining));
+}
+EXPORT_SYMBOL_GPL(closure_sub);
+
+void closure_put(struct closure *cl)
+{
+        closure_put_after_sub(cl, atomic_dec_return(&cl->remaining));
+}
+EXPORT_SYMBOL_GPL(closure_put);
+
+static void set_waiting(struct closure *cl, unsigned long f)
+{
+#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
+        cl->waiting_on = f;
+#endif
+}
+
+void __closure_wake_up(struct closure_waitlist *wait_list)
+{
+        struct llist_node *list;
+        struct closure *cl;
+        struct llist_node *reverse = NULL;
+
+        list = llist_del_all(&wait_list->list);
+
+        /* We first reverse the list to preserve FIFO ordering and fairness */
+
+        while (list) {
+                struct llist_node *t = list;
+                list = llist_next(list);
+
+                t->next = reverse;
+                reverse = t;
+        }
+
+        /* Then do the wakeups */
+
+        while (reverse) {
+                cl = container_of(reverse, struct closure, list);
+                reverse = llist_next(reverse);
+
+                set_waiting(cl, 0);
+                closure_sub(cl, CLOSURE_WAITING + 1);
+        }
+}
+EXPORT_SYMBOL_GPL(__closure_wake_up);
+
+bool closure_wait(struct closure_waitlist *list, struct closure *cl)
+{
+        if (atomic_read(&cl->remaining) & CLOSURE_WAITING)
+                return false;
+
+        set_waiting(cl, _RET_IP_);
+        atomic_add(CLOSURE_WAITING + 1, &cl->remaining);
+        llist_add(&cl->list, &list->list);
+
+        return true;
+}
+EXPORT_SYMBOL_GPL(closure_wait);
+
+/**
+ * closure_sync() - sleep until a closure a closure has nothing left to wait on
+ *
+ * Sleeps until the refcount hits 1 - the thread that's running the closure owns
+ * the last refcount.
+ */
+void closure_sync(struct closure *cl)
+{
+        while (1) {
+                __closure_start_sleep(cl);
+                closure_set_ret_ip(cl);
+
+                if ((atomic_read(&cl->remaining) &
+                     CLOSURE_REMAINING_MASK) == 1)
+                        break;
+
+                schedule();
+        }
+
+        __closure_end_sleep(cl);
+}
+EXPORT_SYMBOL_GPL(closure_sync);
+
+/**
+ * closure_trylock() - try to acquire the closure, without waiting
+ * @cl:         closure to lock
+ *
+ * Returns true if the closure was succesfully locked.
+ */
+bool closure_trylock(struct closure *cl, struct closure *parent)
+{
+        if (atomic_cmpxchg(&cl->remaining, -1,
+                           CLOSURE_REMAINING_INITIALIZER) != -1)
+                return false;
+
+        closure_set_ret_ip(cl);
+
+        smp_mb();
+        cl->parent = parent;
+        if (parent)
+                closure_get(parent);
+
+        closure_debug_create(cl);
+        return true;
+}
+EXPORT_SYMBOL_GPL(closure_trylock);
+
+void __closure_lock(struct closure *cl, struct closure *parent,
+                    struct closure_waitlist *wait_list)
+{
+        struct closure wait;
+        closure_init_stack(&wait);
+
+        while (1) {
+                if (closure_trylock(cl, parent))
+                        return;
+
+                closure_wait_event_sync(wait_list, &wait,
+                                        atomic_read(&cl->remaining) == -1);
+        }
+}
+EXPORT_SYMBOL_GPL(__closure_lock);
+
+static void closure_delay_timer_fn(unsigned long data)
+{
+        struct closure *cl = (struct closure *) data;
+        closure_sub(cl, CLOSURE_TIMER + 1);
+}
+
+void do_closure_timer_init(struct closure *cl)
+{
+        struct timer_list *timer = closure_timer(cl);
+
+        init_timer(timer);
+        timer->data     = (unsigned long) cl;
+        timer->function = closure_delay_timer_fn;
+}
+EXPORT_SYMBOL_GPL(do_closure_timer_init);
+
+bool __closure_delay(struct closure *cl, unsigned long delay,
+                     struct timer_list *timer)
+{
+        if (atomic_read(&cl->remaining) & CLOSURE_TIMER)
+                return false;
+
+        BUG_ON(timer_pending(timer));
+
+        timer->expires  = jiffies + delay;
+
+        atomic_add(CLOSURE_TIMER + 1, &cl->remaining);
+        add_timer(timer);
+        return true;
+}
+EXPORT_SYMBOL_GPL(__closure_delay);
+
+void __closure_flush(struct closure *cl, struct timer_list *timer)
+{
+        if (del_timer(timer))
+                closure_sub(cl, CLOSURE_TIMER + 1);
+}
+EXPORT_SYMBOL_GPL(__closure_flush);
+
+void __closure_flush_sync(struct closure *cl, struct timer_list *timer)
+{
+        if (del_timer_sync(timer))
+                closure_sub(cl, CLOSURE_TIMER + 1);
+}
+EXPORT_SYMBOL_GPL(__closure_flush_sync);
+
+#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
+
+static LIST_HEAD(closure_list);
+static DEFINE_SPINLOCK(closure_list_lock);
+
+void closure_debug_create(struct closure *cl)
+{
+        unsigned long flags;
+
+        BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE);
+        cl->magic = CLOSURE_MAGIC_ALIVE;
+
+        spin_lock_irqsave(&closure_list_lock, flags);
+        list_add(&cl->all, &closure_list);
+        spin_unlock_irqrestore(&closure_list_lock, flags);
+}
+EXPORT_SYMBOL_GPL(closure_debug_create);
+
+void closure_debug_destroy(struct closure *cl)
+{
+        unsigned long flags;
+
+        BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE);
+        cl->magic = CLOSURE_MAGIC_DEAD;
+
+        spin_lock_irqsave(&closure_list_lock, flags);
+        list_del(&cl->all);
+        spin_unlock_irqrestore(&closure_list_lock, flags);
+}
+EXPORT_SYMBOL_GPL(closure_debug_destroy);
+
+static struct dentry *debug;
+
+#define work_data_bits(work) ((unsigned long *)(&(work)->data))
+
+static int debug_seq_show(struct seq_file *f, void *data)
+{
+        struct closure *cl;
+        spin_lock_irq(&closure_list_lock);
+
+        list_for_each_entry(cl, &closure_list, all) {
+                int r = atomic_read(&cl->remaining);
+
+                seq_printf(f, "%p: %pF -> %pf p %p r %i ",
+                           cl, (void *) cl->ip, cl->fn, cl->parent,
+                           r & CLOSURE_REMAINING_MASK);
+
+                seq_printf(f, "%s%s%s%s%s%s\n",
+                           test_bit(WORK_STRUCT_PENDING,
+                                    work_data_bits(&cl->work)) ? "Q" : "",
+                           r & CLOSURE_RUNNING  ? "R" : "",
+                           r & CLOSURE_BLOCKING ? "B" : "",
+                           r & CLOSURE_STACK    ? "S" : "",
+                           r & CLOSURE_SLEEPING ? "Sl" : "",
+                           r & CLOSURE_TIMER    ? "T" : "");
+
+                if (r & CLOSURE_WAITING)
+                        seq_printf(f, " W %pF\n",
+                                   (void *) cl->waiting_on);
+
+                seq_printf(f, "\n");
+        }
+
+        spin_unlock_irq(&closure_list_lock);
+        return 0;
+}
+
+static int debug_seq_open(struct inode *inode, struct file *file)
+{
+        return single_open(file, debug_seq_show, NULL);
+}
+
+static const struct file_operations debug_ops = {
+        .owner          = THIS_MODULE,
+        .open           = debug_seq_open,
+        .read           = seq_read,
+        .release        = single_release
+};
+
+int __init closure_debug_init(void)
+{
+        debug = debugfs_create_file("closures", 0400, NULL, NULL, &debug_ops);
+        return 0;
+}
+
+module_init(closure_debug_init);
+
+#endif
+
+MODULE_AUTHOR("Kent Overstreet <koverstreet@google.com>");
+MODULE_LICENSE("GPL");
diff --git a/drivers/md/bcache/closure.h b/drivers/md/bcache/closure.h
new file mode 100644
index 000000000000..3f31d599ea56
--- /dev/null
+++ b/drivers/md/bcache/closure.h
@@ -0,0 +1,670 @@
+#ifndef _LINUX_CLOSURE_H
+#define _LINUX_CLOSURE_H
+
+#include <linux/llist.h>
+#include <linux/sched.h>
+#include <linux/workqueue.h>
+
+/*
+ * Closure is perhaps the most overused and abused term in computer science, but
+ * since I've been unable to come up with anything better you're stuck with it
+ * again.
+ *
+ * What are closures?
+ *
+ * They embed a refcount. The basic idea is they count "things that are in
+ * progress" - in flight bios, some other thread that's doing something else -
+ * anything you might want to wait on.
+ *
+ * The refcount may be manipulated with closure_get() and closure_put().
+ * closure_put() is where many of the interesting things happen, when it causes
+ * the refcount to go to 0.
+ *
+ * Closures can be used to wait on things both synchronously and asynchronously,
+ * and synchronous and asynchronous use can be mixed without restriction. To
+ * wait synchronously, use closure_sync() - you will sleep until your closure's
+ * refcount hits 1.
+ *
+ * To wait asynchronously, use
+ *   continue_at(cl, next_function, workqueue);
+ *
+ * passing it, as you might expect, the function to run when nothing is pending
+ * and the workqueue to run that function out of.
+ *
+ * continue_at() also, critically, is a macro that returns the calling function.
+ * There's good reason for this.
+ *
+ * To use safely closures asynchronously, they must always have a refcount while
+ * they are running owned by the thread that is running them. Otherwise, suppose
+ * you submit some bios and wish to have a function run when they all complete:
+ *
+ * foo_endio(struct bio *bio, int error)
+ * {
+ *      closure_put(cl);
+ * }
+ *
+ * closure_init(cl);
+ *
+ * do_stuff();
+ * closure_get(cl);
+ * bio1->bi_endio = foo_endio;
+ * bio_submit(bio1);
+ *
+ * do_more_stuff();
+ * closure_get(cl);
+ * bio2->bi_endio = foo_endio;
+ * bio_submit(bio2);
+ *
+ * continue_at(cl, complete_some_read, system_wq);
+ *
+ * If closure's refcount started at 0, complete_some_read() could run before the
+ * second bio was submitted - which is almost always not what you want! More
+ * importantly, it wouldn't be possible to say whether the original thread or
+ * complete_some_read()'s thread owned the closure - and whatever state it was
+ * associated with!
+ *
+ * So, closure_init() initializes a closure's refcount to 1 - and when a
+ * closure_fn is run, the refcount will be reset to 1 first.
+ *
+ * Then, the rule is - if you got the refcount with closure_get(), release it
+ * with closure_put() (i.e, in a bio->bi_endio function). If you have a refcount
+ * on a closure because you called closure_init() or you were run out of a
+ * closure - _always_ use continue_at(). Doing so consistently will help
+ * eliminate an entire class of particularly pernicious races.
+ *
+ * For a closure to wait on an arbitrary event, we need to introduce waitlists:
+ *
+ * struct closure_waitlist list;
+ * closure_wait_event(list, cl, condition);
+ * closure_wake_up(wait_list);
+ *
+ * These work analagously to wait_event() and wake_up() - except that instead of
+ * operating on the current thread (for wait_event()) and lists of threads, they
+ * operate on an explicit closure and lists of closures.
+ *
+ * Because it's a closure we can now wait either synchronously or
+ * asynchronously. closure_wait_event() returns the current value of the
+ * condition, and if it returned false continue_at() or closure_sync() can be
+ * used to wait for it to become true.
+ *
+ * It's useful for waiting on things when you can't sleep in the context in
+ * which you must check the condition (perhaps a spinlock held, or you might be
+ * beneath generic_make_request() - in which case you can't sleep on IO).
+ *
+ * closure_wait_event() will wait either synchronously or asynchronously,
+ * depending on whether the closure is in blocking mode or not. You can pick a
+ * mode explicitly with closure_wait_event_sync() and
+ * closure_wait_event_async(), which do just what you might expect.
+ *
+ * Lastly, you might have a wait list dedicated to a specific event, and have no
+ * need for specifying the condition - you just want to wait until someone runs
+ * closure_wake_up() on the appropriate wait list. In that case, just use
+ * closure_wait(). It will return either true or false, depending on whether the
+ * closure was already on a wait list or not - a closure can only be on one wait
+ * list at a time.
+ *
+ * Parents:
+ *
+ * closure_init() takes two arguments - it takes the closure to initialize, and
+ * a (possibly null) parent.
+ *
+ * If parent is non null, the new closure will have a refcount for its lifetime;
+ * a closure is considered to be "finished" when its refcount hits 0 and the
+ * function to run is null. Hence
+ *
+ * continue_at(cl, NULL, NULL);
+ *
+ * returns up the (spaghetti) stack of closures, precisely like normal return
+ * returns up the C stack. continue_at() with non null fn is better thought of
+ * as doing a tail call.
+ *
+ * All this implies that a closure should typically be embedded in a particular
+ * struct (which its refcount will normally control the lifetime of), and that
+ * struct can very much be thought of as a stack frame.
+ *
+ * Locking:
+ *
+ * Closures are based on work items but they can be thought of as more like
+ * threads - in that like threads and unlike work items they have a well
+ * defined lifetime; they are created (with closure_init()) and eventually
+ * complete after a continue_at(cl, NULL, NULL).
+ *
+ * Suppose you've got some larger structure with a closure embedded in it that's
+ * used for periodically doing garbage collection. You only want one garbage
+ * collection happening at a time, so the natural thing to do is protect it with
+ * a lock. However, it's difficult to use a lock protecting a closure correctly
+ * because the unlock should come after the last continue_to() (additionally, if
+ * you're using the closure asynchronously a mutex won't work since a mutex has
+ * to be unlocked by the same process that locked it).
+ *
+ * So to make it less error prone and more efficient, we also have the ability
+ * to use closures as locks:
+ *
+ * closure_init_unlocked();
+ * closure_trylock();
+ *
+ * That's all we need for trylock() - the last closure_put() implicitly unlocks
+ * it for you.  But for closure_lock(), we also need a wait list:
+ *
+ * struct closure_with_waitlist frobnicator_cl;
+ *
+ * closure_init_unlocked(&frobnicator_cl);
+ * closure_lock(&frobnicator_cl);
+ *
+ * A closure_with_waitlist embeds a closure and a wait list - much like struct
+ * delayed_work embeds a work item and a timer_list. The important thing is, use
+ * it exactly like you would a regular closure and closure_put() will magically
+ * handle everything for you.
+ *
+ * We've got closures that embed timers, too. They're called, appropriately
+ * enough:
+ * struct closure_with_timer;
+ *
+ * This gives you access to closure_delay(). It takes a refcount for a specified
+ * number of jiffies - you could then call closure_sync() (for a slightly
+ * convoluted version of msleep()) or continue_at() - which gives you the same
+ * effect as using a delayed work item, except you can reuse the work_struct
+ * already embedded in struct closure.
+ *
+ * Lastly, there's struct closure_with_waitlist_and_timer. It does what you
+ * probably expect, if you happen to need the features of both. (You don't
+ * really want to know how all this is implemented, but if I've done my job
+ * right you shouldn't have to care).
+ */
+
+struct closure;
+typedef void (closure_fn) (struct closure *);
+
+struct closure_waitlist {
+        struct llist_head       list;
+};
+
+enum closure_type {
+        TYPE_closure                            = 0,
+        TYPE_closure_with_waitlist              = 1,
+        TYPE_closure_with_timer                 = 2,
+        TYPE_closure_with_waitlist_and_timer    = 3,
+        MAX_CLOSURE_TYPE                        = 3,
+};
+
+enum closure_state {
+        /*
+         * CLOSURE_BLOCKING: Causes closure_wait_event() to block, instead of
+         * waiting asynchronously
+         *
+         * CLOSURE_WAITING: Set iff the closure is on a waitlist. Must be set by
+         * the thread that owns the closure, and cleared by the thread that's
+         * waking up the closure.
+         *
+         * CLOSURE_SLEEPING: Must be set before a thread uses a closure to sleep
+         * - indicates that cl->task is valid and closure_put() may wake it up.
+         * Only set or cleared by the thread that owns the closure.
+         *
+         * CLOSURE_TIMER: Analagous to CLOSURE_WAITING, indicates that a closure
+         * has an outstanding timer. Must be set by the thread that owns the
+         * closure, and cleared by the timer function when the timer goes off.
+         *
+         * The rest are for debugging and don't affect behaviour:
+         *
+         * CLOSURE_RUNNING: Set when a closure is running (i.e. by
+         * closure_init() and when closure_put() runs then next function), and
+         * must be cleared before remaining hits 0. Primarily to help guard
+         * against incorrect usage and accidentally transferring references.
+         * continue_at() and closure_return() clear it for you, if you're doing
+         * something unusual you can use closure_set_dead() which also helps
+         * annotate where references are being transferred.
+         *
+         * CLOSURE_STACK: Sanity check - remaining should never hit 0 on a
+         * closure with this flag set
+         */
+
+        CLOSURE_BITS_START      = (1 << 19),
+        CLOSURE_DESTRUCTOR      = (1 << 19),
+        CLOSURE_BLOCKING        = (1 << 21),
+        CLOSURE_WAITING         = (1 << 23),
+        CLOSURE_SLEEPING        = (1 << 25),
+        CLOSURE_TIMER           = (1 << 27),
+        CLOSURE_RUNNING         = (1 << 29),
+        CLOSURE_STACK           = (1 << 31),
+};
+
+#define CLOSURE_GUARD_MASK                                      \
+        ((CLOSURE_DESTRUCTOR|CLOSURE_BLOCKING|CLOSURE_WAITING|  \
+          CLOSURE_SLEEPING|CLOSURE_TIMER|CLOSURE_RUNNING|CLOSURE_STACK) << 1)
+
+#define CLOSURE_REMAINING_MASK          (CLOSURE_BITS_START - 1)
+#define CLOSURE_REMAINING_INITIALIZER   (1|CLOSURE_RUNNING)
+
+struct closure {
+        union {
+                struct {
+                        struct workqueue_struct *wq;
+                        struct task_struct      *task;
+                        struct llist_node       list;
+                        closure_fn              *fn;
+                };
+                struct work_struct      work;
+        };
+
+        struct closure          *parent;
+
+        atomic_t                remaining;
+
+        enum closure_type       type;
+
+#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
+#define CLOSURE_MAGIC_DEAD      0xc054dead
+#define CLOSURE_MAGIC_ALIVE     0xc054a11e
+
+        unsigned                magic;
+        struct list_head        all;
+        unsigned long           ip;
+        unsigned long           waiting_on;
+#endif
+};
+
+struct closure_with_waitlist {
+        struct closure          cl;
+        struct closure_waitlist wait;
+};
+
+struct closure_with_timer {
+        struct closure          cl;
+        struct timer_list       timer;
+};
+
+struct closure_with_waitlist_and_timer {
+        struct closure          cl;
+        struct closure_waitlist wait;
+        struct timer_list       timer;
+};
+
+extern unsigned invalid_closure_type(void);
+
+#define __CLOSURE_TYPE(cl, _t)                                          \
+          __builtin_types_compatible_p(typeof(cl), struct _t)           \
+                ? TYPE_ ## _t :                                         \
+
+#define __closure_type(cl)                                              \
+(                                                                       \
+        __CLOSURE_TYPE(cl, closure)                                     \
+        __CLOSURE_TYPE(cl, closure_with_waitlist)                       \
+        __CLOSURE_TYPE(cl, closure_with_timer)                          \
+        __CLOSURE_TYPE(cl, closure_with_waitlist_and_timer)             \
+        invalid_closure_type()                                          \
+)
+
+void closure_sub(struct closure *cl, int v);
+void closure_put(struct closure *cl);
+void closure_queue(struct closure *cl);
+void __closure_wake_up(struct closure_waitlist *list);
+bool closure_wait(struct closure_waitlist *list, struct closure *cl);
+void closure_sync(struct closure *cl);
+
+bool closure_trylock(struct closure *cl, struct closure *parent);
+void __closure_lock(struct closure *cl, struct closure *parent,
+                    struct closure_waitlist *wait_list);
+
+void do_closure_timer_init(struct closure *cl);
+bool __closure_delay(struct closure *cl, unsigned long delay,
+                     struct timer_list *timer);
+void __closure_flush(struct closure *cl, struct timer_list *timer);
+void __closure_flush_sync(struct closure *cl, struct timer_list *timer);
+
+#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
+
+void closure_debug_create(struct closure *cl);
+void closure_debug_destroy(struct closure *cl);
+
+#else
+
+static inline void closure_debug_create(struct closure *cl) {}
+static inline void closure_debug_destroy(struct closure *cl) {}
+
+#endif
+
+static inline void closure_set_ip(struct closure *cl)
+{
+#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
+        cl->ip = _THIS_IP_;
+#endif
+}
+
+static inline void closure_set_ret_ip(struct closure *cl)
+{
+#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
+        cl->ip = _RET_IP_;
+#endif
+}
+
+static inline void closure_get(struct closure *cl)
+{
+#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
+        BUG_ON((atomic_inc_return(&cl->remaining) &
+                CLOSURE_REMAINING_MASK) <= 1);
+#else
+        atomic_inc(&cl->remaining);
+#endif
+}
+
+static inline void closure_set_stopped(struct closure *cl)
+{
+        atomic_sub(CLOSURE_RUNNING, &cl->remaining);
+}
+
+static inline bool closure_is_stopped(struct closure *cl)
+{
+        return !(atomic_read(&cl->remaining) & CLOSURE_RUNNING);
+}
+
+static inline bool closure_is_unlocked(struct closure *cl)
+{
+        return atomic_read(&cl->remaining) == -1;
+}
+
+static inline void do_closure_init(struct closure *cl, struct closure *parent,
+                                   bool running)
+{
+        switch (cl->type) {
+        case TYPE_closure_with_timer:
+        case TYPE_closure_with_waitlist_and_timer:
+                do_closure_timer_init(cl);
+        default:
+                break;
+        }
+
+        cl->parent = parent;
+        if (parent)
+                closure_get(parent);
+
+        if (running) {
+                closure_debug_create(cl);
+                atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER);
+        } else
+                atomic_set(&cl->remaining, -1);
+
+        closure_set_ip(cl);
+}
+
+/*
+ * Hack to get at the embedded closure if there is one, by doing an unsafe cast:
+ * the result of __closure_type() is thrown away, it's used merely for type
+ * checking.
+ */
+#define __to_internal_closure(cl)                               \
+({                                                              \
+        BUILD_BUG_ON(__closure_type(*cl) > MAX_CLOSURE_TYPE);   \
+        (struct closure *) cl;                                  \
+})
+
+#define closure_init_type(cl, parent, running)                  \
+do {                                                            \
+        struct closure *_cl = __to_internal_closure(cl);        \
+        _cl->type = __closure_type(*(cl));                      \
+        do_closure_init(_cl, parent, running);                  \
+} while (0)
+
+/**
+ * __closure_init() - Initialize a closure, skipping the memset()
+ *
+ * May be used instead of closure_init() when memory has already been zeroed.
+ */
+#define __closure_init(cl, parent)                              \
+        closure_init_type(cl, parent, true)
+
+/**
+ * closure_init() - Initialize a closure, setting the refcount to 1
+ * @cl:         closure to initialize
+ * @parent:     parent of the new closure. cl will take a refcount on it for its
+ *              lifetime; may be NULL.
+ */
+#define closure_init(cl, parent)                                \
+do {                                                            \
+        memset((cl), 0, sizeof(*(cl)));                         \
+        __closure_init(cl, parent);                             \
+} while (0)
+
+static inline void closure_init_stack(struct closure *cl)
+{
+        memset(cl, 0, sizeof(struct closure));
+        atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER|
+                   CLOSURE_BLOCKING|CLOSURE_STACK);
+}
+
+/**
+ * closure_init_unlocked() - Initialize a closure but leave it unlocked.
+ * @cl:         closure to initialize
+ *
+ * For when the closure will be used as a lock. The closure may not be used
+ * until after a closure_lock() or closure_trylock().
+ */
+#define closure_init_unlocked(cl)                               \
+do {                                                            \
+        memset((cl), 0, sizeof(*(cl)));                         \
+        closure_init_type(cl, NULL, false);                     \
+} while (0)
+
+/**
+ * closure_lock() - lock and initialize a closure.
+ * @cl:         the closure to lock
+ * @parent:     the new parent for this closure
+ *
+ * The closure must be of one of the types that has a waitlist (otherwise we
+ * wouldn't be able to sleep on contention).
+ *
+ * @parent has exactly the same meaning as in closure_init(); if non null, the
+ * closure will take a reference on @parent which will be released when it is
+ * unlocked.
+ */
+#define closure_lock(cl, parent)                                \
+        __closure_lock(__to_internal_closure(cl), parent, &(cl)->wait)
+
+/**
+ * closure_delay() - delay some number of jiffies
+ * @cl:         the closure that will sleep
+ * @delay:      the delay in jiffies
+ *
+ * Takes a refcount on @cl which will be released after @delay jiffies; this may
+ * be used to have a function run after a delay with continue_at(), or
+ * closure_sync() may be used for a convoluted version of msleep().
+ */
+#define closure_delay(cl, delay)                        \
+        __closure_delay(__to_internal_closure(cl), delay, &(cl)->timer)
+
+#define closure_flush(cl)                               \
+        __closure_flush(__to_internal_closure(cl), &(cl)->timer)
+
+#define closure_flush_sync(cl)                          \
+        __closure_flush_sync(__to_internal_closure(cl), &(cl)->timer)
+
+static inline void __closure_end_sleep(struct closure *cl)
+{
+        __set_current_state(TASK_RUNNING);
+
+        if (atomic_read(&cl->remaining) & CLOSURE_SLEEPING)
+                atomic_sub(CLOSURE_SLEEPING, &cl->remaining);
+}
+
+static inline void __closure_start_sleep(struct closure *cl)
+{
+        closure_set_ip(cl);
+        cl->task = current;
+        set_current_state(TASK_UNINTERRUPTIBLE);
+
+        if (!(atomic_read(&cl->remaining) & CLOSURE_SLEEPING))
+                atomic_add(CLOSURE_SLEEPING, &cl->remaining);
+}
+
+/**
+ * closure_blocking() - returns true if the closure is in blocking mode.
+ *
+ * If a closure is in blocking mode, closure_wait_event() will sleep until the
+ * condition is true instead of waiting asynchronously.
+ */
+static inline bool closure_blocking(struct closure *cl)
+{
+        return atomic_read(&cl->remaining) & CLOSURE_BLOCKING;
+}
+
+/**
+ * set_closure_blocking() - put a closure in blocking mode.
+ *
+ * If a closure is in blocking mode, closure_wait_event() will sleep until the
+ * condition is true instead of waiting asynchronously.
+ *
+ * Not thread safe - can only be called by the thread running the closure.
+ */
+static inline void set_closure_blocking(struct closure *cl)
+{
+        if (!closure_blocking(cl))
+                atomic_add(CLOSURE_BLOCKING, &cl->remaining);
+}
+
+/*
+ * Not thread safe - can only be called by the thread running the closure.
+ */
+static inline void clear_closure_blocking(struct closure *cl)
+{
+        if (closure_blocking(cl))
+                atomic_sub(CLOSURE_BLOCKING, &cl->remaining);
+}
+
+/**
+ * closure_wake_up() - wake up all closures on a wait list.
+ */
+static inline void closure_wake_up(struct closure_waitlist *list)
+{
+        smp_mb();
+        __closure_wake_up(list);
+}
+
+/*
+ * Wait on an event, synchronously or asynchronously - analogous to wait_event()
+ * but for closures.
+ *
+ * The loop is oddly structured so as to avoid a race; we must check the
+ * condition again after we've added ourself to the waitlist. We know if we were
+ * already on the waitlist because closure_wait() returns false; thus, we only
+ * schedule or break if closure_wait() returns false. If it returns true, we
+ * just loop again - rechecking the condition.
+ *
+ * The __closure_wake_up() is necessary because we may race with the event
+ * becoming true; i.e. we see event false -> wait -> recheck condition, but the
+ * thread that made the event true may have called closure_wake_up() before we
+ * added ourself to the wait list.
+ *
+ * We have to call closure_sync() at the end instead of just
+ * __closure_end_sleep() because a different thread might've called
+ * closure_wake_up() before us and gotten preempted before they dropped the
+ * refcount on our closure. If this was a stack allocated closure, that would be
+ * bad.
+ */
+#define __closure_wait_event(list, cl, condition, _block)               \
+({                                                                      \
+        bool block = _block;                                            \
+        typeof(condition) ret;                                          \
+                                                                        \
+        while (1) {                                                     \
+                ret = (condition);                                      \
+                if (ret) {                                              \
+                        __closure_wake_up(list);                        \
+                        if (block)                                      \
+                                closure_sync(cl);                       \
+                                                                        \
+                        break;                                          \
+                }                                                       \
+                                                                        \
+                if (block)                                              \
+                        __closure_start_sleep(cl);                      \
+                                                                        \
+                if (!closure_wait(list, cl)) {                          \
+                        if (!block)                                     \
+                                break;                                  \
+                                                                        \
+                        schedule();                                     \
+                }                                                       \
+        }                                                               \
+                                                                        \
+        ret;                                                            \
+})
+
+/**
+ * closure_wait_event() - wait on a condition, synchronously or asynchronously.
+ * @list:       the wait list to wait on
+ * @cl:         the closure that is doing the waiting
+ * @condition:  a C expression for the event to wait for
+ *
+ * If the closure is in blocking mode, sleeps until the @condition evaluates to
+ * true - exactly like wait_event().
+ *
+ * If the closure is not in blocking mode, waits asynchronously; if the
+ * condition is currently false the @cl is put onto @list and returns. @list
+ * owns a refcount on @cl; closure_sync() or continue_at() may be used later to
+ * wait for another thread to wake up @list, which drops the refcount on @cl.
+ *
+ * Returns the value of @condition; @cl will be on @list iff @condition was
+ * false.
+ *
+ * closure_wake_up(@list) must be called after changing any variable that could
+ * cause @condition to become true.
+ */
+#define closure_wait_event(list, cl, condition)                         \
+        __closure_wait_event(list, cl, condition, closure_blocking(cl))
+
+#define closure_wait_event_async(list, cl, condition)                   \
+        __closure_wait_event(list, cl, condition, false)
+
+#define closure_wait_event_sync(list, cl, condition)                    \
+        __closure_wait_event(list, cl, condition, true)
+
+static inline void set_closure_fn(struct closure *cl, closure_fn *fn,
+                                  struct workqueue_struct *wq)
+{
+        BUG_ON(object_is_on_stack(cl));
+        closure_set_ip(cl);
+        cl->fn = fn;
+        cl->wq = wq;
+        /* between atomic_dec() in closure_put() */
+        smp_mb__before_atomic_dec();
+}
+
+#define continue_at(_cl, _fn, _wq)                                      \
+do {                                                                    \
+        set_closure_fn(_cl, _fn, _wq);                                  \
+        closure_sub(_cl, CLOSURE_RUNNING + 1);                          \
+        return;                                                         \
+} while (0)
+
+#define closure_return(_cl)     continue_at((_cl), NULL, NULL)
+
+#define continue_at_nobarrier(_cl, _fn, _wq)                            \
+do {                                                                    \
+        set_closure_fn(_cl, _fn, _wq);                                  \
+        closure_queue(cl);                                              \
+        return;                                                         \
+} while (0)
+
+#define closure_return_with_destructor(_cl, _destructor)                \
+do {                                                                    \
+        set_closure_fn(_cl, _destructor, NULL);                         \
+        closure_sub(_cl, CLOSURE_RUNNING - CLOSURE_DESTRUCTOR + 1);     \
+        return;                                                         \
+} while (0)
+
+static inline void closure_call(struct closure *cl, closure_fn fn,
+                                struct workqueue_struct *wq,
+                                struct closure *parent)
+{
+        closure_init(cl, parent);
+        continue_at_nobarrier(cl, fn, wq);
+}
+
+static inline void closure_trylock_call(struct closure *cl, closure_fn fn,
+                                        struct workqueue_struct *wq,
+                                        struct closure *parent)
+{
+        if (closure_trylock(cl, parent))
+                continue_at_nobarrier(cl, fn, wq);
+}
+
+#endif /* _LINUX_CLOSURE_H */
diff --git a/drivers/md/bcache/debug.c b/drivers/md/bcache/debug.c
new file mode 100644
index 000000000000..4b37ef2b80e5
--- /dev/null
+++ b/drivers/md/bcache/debug.c
@@ -0,0 +1,563 @@
+/*
+ * Assorted bcache debug code
+ *
+ * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
+ * Copyright 2012 Google, Inc.
+ */
+
+#include "bcache.h"
+#include "btree.h"
+#include "debug.h"
+#include "request.h"
+
+#include <linux/console.h>
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/random.h>
+#include <linux/seq_file.h>
+
+static struct dentry *debug;
+
+const char *bch_ptr_status(struct cache_set *c, const struct bkey *k)
+{
+        unsigned i;
+
+        for (i = 0; i < KEY_PTRS(k); i++)
+                if (ptr_available(c, k, i)) {
+                        struct cache *ca = PTR_CACHE(c, k, i);
+                        size_t bucket = PTR_BUCKET_NR(c, k, i);
+                        size_t r = bucket_remainder(c, PTR_OFFSET(k, i));
+
+                        if (KEY_SIZE(k) + r > c->sb.bucket_size)
+                                return "bad, length too big";
+                        if (bucket <  ca->sb.first_bucket)
+                                return "bad, short offset";
+                        if (bucket >= ca->sb.nbuckets)
+                                return "bad, offset past end of device";
+                        if (ptr_stale(c, k, i))
+                                return "stale";
+                }
+
+        if (!bkey_cmp(k, &ZERO_KEY))
+                return "bad, null key";
+        if (!KEY_PTRS(k))
+                return "bad, no pointers";
+        if (!KEY_SIZE(k))
+                return "zeroed key";
+        return "";
+}
+
+struct keyprint_hack bch_pkey(const struct bkey *k)
+{
+        unsigned i = 0;
+        struct keyprint_hack r;
+        char *out = r.s, *end = r.s + KEYHACK_SIZE;
+
+#define p(...)  (out += scnprintf(out, end - out, __VA_ARGS__))
+
+        p("%llu:%llu len %llu -> [", KEY_INODE(k), KEY_OFFSET(k), KEY_SIZE(k));
+
+        if (KEY_PTRS(k))
+                while (1) {
+                        p("%llu:%llu gen %llu",
+                          PTR_DEV(k, i), PTR_OFFSET(k, i), PTR_GEN(k, i));
+
+                        if (++i == KEY_PTRS(k))
+                                break;
+
+                        p(", ");
+                }
+
+        p("]");
+
+        if (KEY_DIRTY(k))
+                p(" dirty");
+        if (KEY_CSUM(k))
+                p(" cs%llu %llx", KEY_CSUM(k), k->ptr[1]);
+#undef p
+        return r;
+}
+
+struct keyprint_hack bch_pbtree(const struct btree *b)
+{
+        struct keyprint_hack r;
+
+        snprintf(r.s, 40, "%li level %i/%i", PTR_BUCKET_NR(b->c, &b->key, 0),
+                 b->level, b->c->root ? b->c->root->level : -1);
+        return r;
+}
+
+#if defined(CONFIG_BCACHE_DEBUG) || defined(CONFIG_BCACHE_EDEBUG)
+
+static bool skipped_backwards(struct btree *b, struct bkey *k)
+{
+        return bkey_cmp(k, (!b->level)
+                        ? &START_KEY(bkey_next(k))
+                        : bkey_next(k)) > 0;
+}
+
+static void dump_bset(struct btree *b, struct bset *i)
+{
+        struct bkey *k;
+        unsigned j;
+
+        for (k = i->start; k < end(i); k = bkey_next(k)) {
+                printk(KERN_ERR "block %zu key %zi/%u: %s", index(i, b),
+                       (uint64_t *) k - i->d, i->keys, pkey(k));
+
+                for (j = 0; j < KEY_PTRS(k); j++) {
+                        size_t n = PTR_BUCKET_NR(b->c, k, j);
+                        printk(" bucket %zu", n);
+
+                        if (n >= b->c->sb.first_bucket && n < b->c->sb.nbuckets)
+                                printk(" prio %i",
+                                       PTR_BUCKET(b->c, k, j)->prio);
+                }
+
+                printk(" %s\n", bch_ptr_status(b->c, k));
+
+                if (bkey_next(k) < end(i) &&
+                    skipped_backwards(b, k))
+                        printk(KERN_ERR "Key skipped backwards\n");
+        }
+}
+
+#endif
+
+#ifdef CONFIG_BCACHE_DEBUG
+
+void bch_btree_verify(struct btree *b, struct bset *new)
+{
+        struct btree *v = b->c->verify_data;
+        struct closure cl;
+        closure_init_stack(&cl);
+
+        if (!b->c->verify)
+                return;
+
+        closure_wait_event(&b->io.wait, &cl,
+                           atomic_read(&b->io.cl.remaining) == -1);
+
+        mutex_lock(&b->c->verify_lock);
+
+        bkey_copy(&v->key, &b->key);
+        v->written = 0;
+        v->level = b->level;
+
+        bch_btree_read(v);
+        closure_wait_event(&v->io.wait, &cl,
+                           atomic_read(&b->io.cl.remaining) == -1);
+
+        if (new->keys != v->sets[0].data->keys ||
+            memcmp(new->start,
+                   v->sets[0].data->start,
+                   (void *) end(new) - (void *) new->start)) {
+                unsigned i, j;
+
+                console_lock();
+
+                printk(KERN_ERR "*** original memory node:\n");
+                for (i = 0; i <= b->nsets; i++)
+                        dump_bset(b, b->sets[i].data);
+
+                printk(KERN_ERR "*** sorted memory node:\n");
+                dump_bset(b, new);
+
+                printk(KERN_ERR "*** on disk node:\n");
+                dump_bset(v, v->sets[0].data);
+
+                for (j = 0; j < new->keys; j++)
+                        if (new->d[j] != v->sets[0].data->d[j])
+                                break;
+
+                console_unlock();
+                panic("verify failed at %u\n", j);
+        }
+
+        mutex_unlock(&b->c->verify_lock);
+}
+
+static void data_verify_endio(struct bio *bio, int error)
+{
+        struct closure *cl = bio->bi_private;
+        closure_put(cl);
+}
+
+void bch_data_verify(struct search *s)
+{
+        char name[BDEVNAME_SIZE];
+        struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
+        struct closure *cl = &s->cl;
+        struct bio *check;
+        struct bio_vec *bv;
+        int i;
+
+        if (!s->unaligned_bvec)
+                bio_for_each_segment(bv, s->orig_bio, i)
+                        bv->bv_offset = 0, bv->bv_len = PAGE_SIZE;
+
+        check = bio_clone(s->orig_bio, GFP_NOIO);
+        if (!check)
+                return;
+
+        if (bio_alloc_pages(check, GFP_NOIO))
+                goto out_put;
+
+        check->bi_rw            = READ_SYNC;
+        check->bi_private       = cl;
+        check->bi_end_io        = data_verify_endio;
+
+        closure_bio_submit(check, cl, &dc->disk);
+        closure_sync(cl);
+
+        bio_for_each_segment(bv, s->orig_bio, i) {
+                void *p1 = kmap(bv->bv_page);
+                void *p2 = kmap(check->bi_io_vec[i].bv_page);
+
+                if (memcmp(p1 + bv->bv_offset,
+                           p2 + bv->bv_offset,
+                           bv->bv_len))
+                        printk(KERN_ERR "bcache (%s): verify failed"
+                               " at sector %llu\n",
+                               bdevname(dc->bdev, name),
+                               (uint64_t) s->orig_bio->bi_sector);
+
+                kunmap(bv->bv_page);
+                kunmap(check->bi_io_vec[i].bv_page);
+        }
+
+        __bio_for_each_segment(bv, check, i, 0)
+                __free_page(bv->bv_page);
+out_put:
+        bio_put(check);
+}
+
+#endif
+
+#ifdef CONFIG_BCACHE_EDEBUG
+
+unsigned bch_count_data(struct btree *b)
+{
+        unsigned ret = 0;
+        struct btree_iter iter;
+        struct bkey *k;
+
+        if (!b->level)
+                for_each_key(b, k, &iter)
+                        ret += KEY_SIZE(k);
+        return ret;
+}
+
+static void vdump_bucket_and_panic(struct btree *b, const char *fmt,
+                                   va_list args)
+{
+        unsigned i;
+
+        console_lock();
+
+        for (i = 0; i <= b->nsets; i++)
+                dump_bset(b, b->sets[i].data);
+
+        vprintk(fmt, args);
+
+        console_unlock();
+
+        panic("at %s\n", pbtree(b));
+}
+
+void bch_check_key_order_msg(struct btree *b, struct bset *i,
+                             const char *fmt, ...)
+{
+        struct bkey *k;
+
+        if (!i->keys)
+                return;
+
+        for (k = i->start; bkey_next(k) < end(i); k = bkey_next(k))
+                if (skipped_backwards(b, k)) {
+                        va_list args;
+                        va_start(args, fmt);
+
+                        vdump_bucket_and_panic(b, fmt, args);
+                        va_end(args);
+                }
+}
+
+void bch_check_keys(struct btree *b, const char *fmt, ...)
+{
+        va_list args;
+        struct bkey *k, *p = NULL;
+        struct btree_iter iter;
+
+        if (b->level)
+                return;
+
+        for_each_key(b, k, &iter) {
+                if (p && bkey_cmp(&START_KEY(p), &START_KEY(k)) > 0) {
+                        printk(KERN_ERR "Keys out of order:\n");
+                        goto bug;
+                }
+
+                if (bch_ptr_invalid(b, k))
+                        continue;
+
+                if (p && bkey_cmp(p, &START_KEY(k)) > 0) {
+                        printk(KERN_ERR "Overlapping keys:\n");
+                        goto bug;
+                }
+                p = k;
+        }
+        return;
+bug:
+        va_start(args, fmt);
+        vdump_bucket_and_panic(b, fmt, args);
+        va_end(args);
+}
+
+#endif
+
+#ifdef CONFIG_DEBUG_FS
+
+/* XXX: cache set refcounting */
+
+struct dump_iterator {
+        char                    buf[PAGE_SIZE];
+        size_t                  bytes;
+        struct cache_set        *c;
+        struct keybuf           keys;
+};
+
+static bool dump_pred(struct keybuf *buf, struct bkey *k)
+{
+        return true;
+}
+
+static ssize_t bch_dump_read(struct file *file, char __user *buf,
+                             size_t size, loff_t *ppos)
+{
+        struct dump_iterator *i = file->private_data;
+        ssize_t ret = 0;
+
+        while (size) {
+                struct keybuf_key *w;
+                unsigned bytes = min(i->bytes, size);
+
+                int err = copy_to_user(buf, i->buf, bytes);
+                if (err)
+                        return err;
+
+                ret      += bytes;
+                buf      += bytes;
+                size     -= bytes;
+                i->bytes -= bytes;
+                memmove(i->buf, i->buf + bytes, i->bytes);
+
+                if (i->bytes)
+                        break;
+
+                w = bch_keybuf_next_rescan(i->c, &i->keys, &MAX_KEY);
+                if (!w)
+                        break;
+
+                i->bytes = snprintf(i->buf, PAGE_SIZE, "%s\n", pkey(&w->key));
+                bch_keybuf_del(&i->keys, w);
+        }
+
+        return ret;
+}
+
+static int bch_dump_open(struct inode *inode, struct file *file)
+{
+        struct cache_set *c = inode->i_private;
+        struct dump_iterator *i;
+
+        i = kzalloc(sizeof(struct dump_iterator), GFP_KERNEL);
+        if (!i)
+                return -ENOMEM;
+
+        file->private_data = i;
+        i->c = c;
+        bch_keybuf_init(&i->keys, dump_pred);
+        i->keys.last_scanned = KEY(0, 0, 0);
+
+        return 0;
+}
+
+static int bch_dump_release(struct inode *inode, struct file *file)
+{
+        kfree(file->private_data);
+        return 0;
+}
+
+static const struct file_operations cache_set_debug_ops = {
+        .owner          = THIS_MODULE,
+        .open           = bch_dump_open,
+        .read           = bch_dump_read,
+        .release        = bch_dump_release
+};
+
+void bch_debug_init_cache_set(struct cache_set *c)
+{
+        if (!IS_ERR_OR_NULL(debug)) {
+                char name[50];
+                snprintf(name, 50, "bcache-%pU", c->sb.set_uuid);
+
+                c->debug = debugfs_create_file(name, 0400, debug, c,
+                                               &cache_set_debug_ops);
+        }
+}
+
+#endif
+
+#ifdef CONFIG_BCACHE_DEBUG
+static ssize_t btree_fuzz(struct kobject *k, struct kobj_attribute *a,
+                          const char *buffer, size_t size)
+{
+        void dump(struct btree *b)
+        {
+                struct bset *i;
+
+                for (i = b->sets[0].data;
+                     index(i, b) < btree_blocks(b) &&
+                     i->seq == b->sets[0].data->seq;
+                     i = ((void *) i) + set_blocks(i, b->c) * block_bytes(b->c))
+                        dump_bset(b, i);
+        }
+
+        struct cache_sb *sb;
+        struct cache_set *c;
+        struct btree *all[3], *b, *fill, *orig;
+        int j;
+
+        struct btree_op op;
+        bch_btree_op_init_stack(&op);
+
+        sb = kzalloc(sizeof(struct cache_sb), GFP_KERNEL);
+        if (!sb)
+                return -ENOMEM;
+
+        sb->bucket_size = 128;
+        sb->block_size = 4;
+
+        c = bch_cache_set_alloc(sb);
+        if (!c)
+                return -ENOMEM;
+
+        for (j = 0; j < 3; j++) {
+                BUG_ON(list_empty(&c->btree_cache));
+                all[j] = list_first_entry(&c->btree_cache, struct btree, list);
+                list_del_init(&all[j]->list);
+
+                all[j]->key = KEY(0, 0, c->sb.bucket_size);
+                bkey_copy_key(&all[j]->key, &MAX_KEY);
+        }
+
+        b = all[0];
+        fill = all[1];
+        orig = all[2];
+
+        while (1) {
+                for (j = 0; j < 3; j++)
+                        all[j]->written = all[j]->nsets = 0;
+
+                bch_bset_init_next(b);
+
+                while (1) {
+                        struct bset *i = write_block(b);
+                        struct bkey *k = op.keys.top;
+                        unsigned rand;
+
+                        bkey_init(k);
+                        rand = get_random_int();
+
+                        op.type = rand & 1
+                                ? BTREE_INSERT
+                                : BTREE_REPLACE;
+                        rand >>= 1;
+
+                        SET_KEY_SIZE(k, bucket_remainder(c, rand));
+                        rand >>= c->bucket_bits;
+                        rand &= 1024 * 512 - 1;
+                        rand += c->sb.bucket_size;
+                        SET_KEY_OFFSET(k, rand);
+#if 0
+                        SET_KEY_PTRS(k, 1);
+#endif
+                        bch_keylist_push(&op.keys);
+                        bch_btree_insert_keys(b, &op);
+
+                        if (should_split(b) ||
+                            set_blocks(i, b->c) !=
+                            __set_blocks(i, i->keys + 15, b->c)) {
+                                i->csum = csum_set(i);
+
+                                memcpy(write_block(fill),
+                                       i, set_bytes(i));
+
+                                b->written += set_blocks(i, b->c);
+                                fill->written = b->written;
+                                if (b->written == btree_blocks(b))
+                                        break;
+
+                                bch_btree_sort_lazy(b);
+                                bch_bset_init_next(b);
+                        }
+                }
+
+                memcpy(orig->sets[0].data,
+                       fill->sets[0].data,
+                       btree_bytes(c));
+
+                bch_btree_sort(b);
+                fill->written = 0;
+                bch_btree_read_done(&fill->io.cl);
+
+                if (b->sets[0].data->keys != fill->sets[0].data->keys ||
+                    memcmp(b->sets[0].data->start,
+                           fill->sets[0].data->start,
+                           b->sets[0].data->keys * sizeof(uint64_t))) {
+                        struct bset *i = b->sets[0].data;
+                        struct bkey *k, *l;
+
+                        for (k = i->start,
+                             l = fill->sets[0].data->start;
+                             k < end(i);
+                             k = bkey_next(k), l = bkey_next(l))
+                                if (bkey_cmp(k, l) ||
+                                    KEY_SIZE(k) != KEY_SIZE(l))
+                                        pr_err("key %zi differs: %s "
+                                               "!= %s", (uint64_t *) k - i->d,
+                                               pkey(k), pkey(l));
+
+                        for (j = 0; j < 3; j++) {
+                                pr_err("**** Set %i ****", j);
+                                dump(all[j]);
+                        }
+                        panic("\n");
+                }
+
+                pr_info("fuzz complete: %i keys", b->sets[0].data->keys);
+        }
+}
+
+kobj_attribute_write(fuzz, btree_fuzz);
+#endif
+
+void bch_debug_exit(void)
+{
+        if (!IS_ERR_OR_NULL(debug))
+                debugfs_remove_recursive(debug);
+}
+
+int __init bch_debug_init(struct kobject *kobj)
+{
+        int ret = 0;
+#ifdef CONFIG_BCACHE_DEBUG
+        ret = sysfs_create_file(kobj, &ksysfs_fuzz.attr);
+        if (ret)
+                return ret;
+#endif
+
+        debug = debugfs_create_dir("bcache", NULL);
+        return ret;
+}
diff --git a/drivers/md/bcache/debug.h b/drivers/md/bcache/debug.h
new file mode 100644
index 000000000000..f9378a218148
--- /dev/null
+++ b/drivers/md/bcache/debug.h
@@ -0,0 +1,54 @@
+#ifndef _BCACHE_DEBUG_H
+#define _BCACHE_DEBUG_H
+
+/* Btree/bkey debug printing */
+
+#define KEYHACK_SIZE 80
+struct keyprint_hack {
+        char s[KEYHACK_SIZE];
+};
+
+struct keyprint_hack bch_pkey(const struct bkey *k);
+struct keyprint_hack bch_pbtree(const struct btree *b);
+#define pkey(k)         (&bch_pkey(k).s[0])
+#define pbtree(b)       (&bch_pbtree(b).s[0])
+
+#ifdef CONFIG_BCACHE_EDEBUG
+
+unsigned bch_count_data(struct btree *);
+void bch_check_key_order_msg(struct btree *, struct bset *, const char *, ...);
+void bch_check_keys(struct btree *, const char *, ...);
+
+#define bch_check_key_order(b, i)                       \
+        bch_check_key_order_msg(b, i, "keys out of order")
+#define EBUG_ON(cond)           BUG_ON(cond)
+
+#else /* EDEBUG */
+
+#define bch_count_data(b)                               0
+#define bch_check_key_order(b, i)                       do {} while (0)
+#define bch_check_key_order_msg(b, i, ...)              do {} while (0)
+#define bch_check_keys(b, ...)                          do {} while (0)
+#define EBUG_ON(cond)                                   do {} while (0)
+
+#endif
+
+#ifdef CONFIG_BCACHE_DEBUG
+
+void bch_btree_verify(struct btree *, struct bset *);
+void bch_data_verify(struct search *);
+
+#else /* DEBUG */
+
+static inline void bch_btree_verify(struct btree *b, struct bset *i) {}
+static inline void bch_data_verify(struct search *s) {};
+
+#endif
+
+#ifdef CONFIG_DEBUG_FS
+void bch_debug_init_cache_set(struct cache_set *);
+#else
+static inline void bch_debug_init_cache_set(struct cache_set *c) {}
+#endif
+
+#endif
diff --git a/drivers/md/bcache/io.c b/drivers/md/bcache/io.c
new file mode 100644
index 000000000000..f565512f6fac
--- /dev/null
+++ b/drivers/md/bcache/io.c
@@ -0,0 +1,390 @@
+/*
+ * Some low level IO code, and hacks for various block layer limitations
+ *
+ * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
+ * Copyright 2012 Google, Inc.
+ */
+
+#include "bcache.h"
+#include "bset.h"
+#include "debug.h"
+
+static void bch_bi_idx_hack_endio(struct bio *bio, int error)
+{
+        struct bio *p = bio->bi_private;
+
+        bio_endio(p, error);
+        bio_put(bio);
+}
+
+static void bch_generic_make_request_hack(struct bio *bio)
+{
+        if (bio->bi_idx) {
+                struct bio *clone = bio_alloc(GFP_NOIO, bio_segments(bio));
+
+                memcpy(clone->bi_io_vec,
+                       bio_iovec(bio),
+                       bio_segments(bio) * sizeof(struct bio_vec));
+
+                clone->bi_sector        = bio->bi_sector;
+                clone->bi_bdev          = bio->bi_bdev;
+                clone->bi_rw            = bio->bi_rw;
+                clone->bi_vcnt          = bio_segments(bio);
+                clone->bi_size          = bio->bi_size;
+
+                clone->bi_private       = bio;
+                clone->bi_end_io        = bch_bi_idx_hack_endio;
+
+                bio = clone;
+        }
+
+        generic_make_request(bio);
+}
+
+/**
+ * bch_bio_split - split a bio
+ * @bio:        bio to split
+ * @sectors:    number of sectors to split from the front of @bio
+ * @gfp:        gfp mask
+ * @bs:         bio set to allocate from
+ *
+ * Allocates and returns a new bio which represents @sectors from the start of
+ * @bio, and updates @bio to represent the remaining sectors.
+ *
+ * If bio_sectors(@bio) was less than or equal to @sectors, returns @bio
+ * unchanged.
+ *
+ * The newly allocated bio will point to @bio's bi_io_vec, if the split was on a
+ * bvec boundry; it is the caller's responsibility to ensure that @bio is not
+ * freed before the split.
+ *
+ * If bch_bio_split() is running under generic_make_request(), it's not safe to
+ * allocate more than one bio from the same bio set. Therefore, if it is running
+ * under generic_make_request() it masks out __GFP_WAIT when doing the
+ * allocation. The caller must check for failure if there's any possibility of
+ * it being called from under generic_make_request(); it is then the caller's
+ * responsibility to retry from a safe context (by e.g. punting to workqueue).
+ */
+struct bio *bch_bio_split(struct bio *bio, int sectors,
+                          gfp_t gfp, struct bio_set *bs)
+{
+        unsigned idx = bio->bi_idx, vcnt = 0, nbytes = sectors << 9;
+        struct bio_vec *bv;
+        struct bio *ret = NULL;
+
+        BUG_ON(sectors <= 0);
+
+        /*
+         * If we're being called from underneath generic_make_request() and we
+         * already allocated any bios from this bio set, we risk deadlock if we
+         * use the mempool. So instead, we possibly fail and let the caller punt
+         * to workqueue or somesuch and retry in a safe context.
+         */
+        if (current->bio_list)
+                gfp &= ~__GFP_WAIT;
+
+        if (sectors >= bio_sectors(bio))
+                return bio;
+
+        if (bio->bi_rw & REQ_DISCARD) {
+                ret = bio_alloc_bioset(gfp, 1, bs);
+                idx = 0;
+                goto out;
+        }
+
+        bio_for_each_segment(bv, bio, idx) {
+                vcnt = idx - bio->bi_idx;
+
+                if (!nbytes) {
+                        ret = bio_alloc_bioset(gfp, vcnt, bs);
+                        if (!ret)
+                                return NULL;
+
+                        memcpy(ret->bi_io_vec, bio_iovec(bio),
+                               sizeof(struct bio_vec) * vcnt);
+
+                        break;
+                } else if (nbytes < bv->bv_len) {
+                        ret = bio_alloc_bioset(gfp, ++vcnt, bs);
+                        if (!ret)
+                                return NULL;
+
+                        memcpy(ret->bi_io_vec, bio_iovec(bio),
+                               sizeof(struct bio_vec) * vcnt);
+
+                        ret->bi_io_vec[vcnt - 1].bv_len = nbytes;
+                        bv->bv_offset   += nbytes;
+                        bv->bv_len      -= nbytes;
+                        break;
+                }
+
+                nbytes -= bv->bv_len;
+        }
+out:
+        ret->bi_bdev    = bio->bi_bdev;
+        ret->bi_sector  = bio->bi_sector;
+        ret->bi_size    = sectors << 9;
+        ret->bi_rw      = bio->bi_rw;
+        ret->bi_vcnt    = vcnt;
+        ret->bi_max_vecs = vcnt;
+
+        bio->bi_sector  += sectors;
+        bio->bi_size    -= sectors << 9;
+        bio->bi_idx      = idx;
+
+        if (bio_integrity(bio)) {
+                if (bio_integrity_clone(ret, bio, gfp)) {
+                        bio_put(ret);
+                        return NULL;
+                }
+
+                bio_integrity_trim(ret, 0, bio_sectors(ret));
+                bio_integrity_trim(bio, bio_sectors(ret), bio_sectors(bio));
+        }
+
+        return ret;
+}
+
+static unsigned bch_bio_max_sectors(struct bio *bio)
+{
+        unsigned ret = bio_sectors(bio);
+        struct request_queue *q = bdev_get_queue(bio->bi_bdev);
+        struct bio_vec *bv, *end = bio_iovec(bio) +
+                min_t(int, bio_segments(bio), queue_max_segments(q));
+
+        struct bvec_merge_data bvm = {
+                .bi_bdev        = bio->bi_bdev,
+                .bi_sector      = bio->bi_sector,
+                .bi_size        = 0,
+                .bi_rw          = bio->bi_rw,
+        };
+
+        if (bio->bi_rw & REQ_DISCARD)
+                return min(ret, q->limits.max_discard_sectors);
+
+        if (bio_segments(bio) > queue_max_segments(q) ||
+            q->merge_bvec_fn) {
+                ret = 0;
+
+                for (bv = bio_iovec(bio); bv < end; bv++) {
+                        if (q->merge_bvec_fn &&
+                            q->merge_bvec_fn(q, &bvm, bv) < (int) bv->bv_len)
+                                break;
+
+                        ret             += bv->bv_len >> 9;
+                        bvm.bi_size     += bv->bv_len;
+                }
+
+                if (ret >= (BIO_MAX_PAGES * PAGE_SIZE) >> 9)
+                        return (BIO_MAX_PAGES * PAGE_SIZE) >> 9;
+        }
+
+        ret = min(ret, queue_max_sectors(q));
+
+        WARN_ON(!ret);
+        ret = max_t(int, ret, bio_iovec(bio)->bv_len >> 9);
+
+        return ret;
+}
+
+static void bch_bio_submit_split_done(struct closure *cl)
+{
+        struct bio_split_hook *s = container_of(cl, struct bio_split_hook, cl);
+
+        s->bio->bi_end_io = s->bi_end_io;
+        s->bio->bi_private = s->bi_private;
+        bio_endio(s->bio, 0);
+
+        closure_debug_destroy(&s->cl);
+        mempool_free(s, s->p->bio_split_hook);
+}
+
+static void bch_bio_submit_split_endio(struct bio *bio, int error)
+{
+        struct closure *cl = bio->bi_private;
+        struct bio_split_hook *s = container_of(cl, struct bio_split_hook, cl);
+
+        if (error)
+                clear_bit(BIO_UPTODATE, &s->bio->bi_flags);
+
+        bio_put(bio);
+        closure_put(cl);
+}
+
+static void __bch_bio_submit_split(struct closure *cl)
+{
+        struct bio_split_hook *s = container_of(cl, struct bio_split_hook, cl);
+        struct bio *bio = s->bio, *n;
+
+        do {
+                n = bch_bio_split(bio, bch_bio_max_sectors(bio),
+                                  GFP_NOIO, s->p->bio_split);
+                if (!n)
+                        continue_at(cl, __bch_bio_submit_split, system_wq);
+
+                n->bi_end_io    = bch_bio_submit_split_endio;
+                n->bi_private   = cl;
+
+                closure_get(cl);
+                bch_generic_make_request_hack(n);
+        } while (n != bio);
+
+        continue_at(cl, bch_bio_submit_split_done, NULL);
+}
+
+void bch_generic_make_request(struct bio *bio, struct bio_split_pool *p)
+{
+        struct bio_split_hook *s;
+
+        if (!bio_has_data(bio) && !(bio->bi_rw & REQ_DISCARD))
+                goto submit;
+
+        if (bio_sectors(bio) <= bch_bio_max_sectors(bio))
+                goto submit;
+
+        s = mempool_alloc(p->bio_split_hook, GFP_NOIO);
+
+        s->bio          = bio;
+        s->p            = p;
+        s->bi_end_io    = bio->bi_end_io;
+        s->bi_private   = bio->bi_private;
+        bio_get(bio);
+
+        closure_call(&s->cl, __bch_bio_submit_split, NULL, NULL);
+        return;
+submit:
+        bch_generic_make_request_hack(bio);
+}
+
+/* Bios with headers */
+
+void bch_bbio_free(struct bio *bio, struct cache_set *c)
+{
+        struct bbio *b = container_of(bio, struct bbio, bio);
+        mempool_free(b, c->bio_meta);
+}
+
+struct bio *bch_bbio_alloc(struct cache_set *c)
+{
+        struct bbio *b = mempool_alloc(c->bio_meta, GFP_NOIO);
+        struct bio *bio = &b->bio;
+
+        bio_init(bio);
+        bio->bi_flags           |= BIO_POOL_NONE << BIO_POOL_OFFSET;
+        bio->bi_max_vecs         = bucket_pages(c);
+        bio->bi_io_vec           = bio->bi_inline_vecs;
+
+        return bio;
+}
+
+void __bch_submit_bbio(struct bio *bio, struct cache_set *c)
+{
+        struct bbio *b = container_of(bio, struct bbio, bio);
+
+        bio->bi_sector  = PTR_OFFSET(&b->key, 0);
+        bio->bi_bdev    = PTR_CACHE(c, &b->key, 0)->bdev;
+
+        b->submit_time_us = local_clock_us();
+        closure_bio_submit(bio, bio->bi_private, PTR_CACHE(c, &b->key, 0));
+}
+
+void bch_submit_bbio(struct bio *bio, struct cache_set *c,
+                     struct bkey *k, unsigned ptr)
+{
+        struct bbio *b = container_of(bio, struct bbio, bio);
+        bch_bkey_copy_single_ptr(&b->key, k, ptr);
+        __bch_submit_bbio(bio, c);
+}
+
+/* IO errors */
+
+void bch_count_io_errors(struct cache *ca, int error, const char *m)
+{
+        /*
+         * The halflife of an error is:
+         * log2(1/2)/log2(127/128) * refresh ~= 88 * refresh
+         */
+
+        if (ca->set->error_decay) {
+                unsigned count = atomic_inc_return(&ca->io_count);
+
+                while (count > ca->set->error_decay) {
+                        unsigned errors;
+                        unsigned old = count;
+                        unsigned new = count - ca->set->error_decay;
+
+                        /*
+                         * First we subtract refresh from count; each time we
+                         * succesfully do so, we rescale the errors once:
+                         */
+
+                        count = atomic_cmpxchg(&ca->io_count, old, new);
+
+                        if (count == old) {
+                                count = new;
+
+                                errors = atomic_read(&ca->io_errors);
+                                do {
+                                        old = errors;
+                                        new = ((uint64_t) errors * 127) / 128;
+                                        errors = atomic_cmpxchg(&ca->io_errors,
+                                                                old, new);
+                                } while (old != errors);
+                        }
+                }
+        }
+
+        if (error) {
+                char buf[BDEVNAME_SIZE];
+                unsigned errors = atomic_add_return(1 << IO_ERROR_SHIFT,
+                                                    &ca->io_errors);
+                errors >>= IO_ERROR_SHIFT;
+
+                if (errors < ca->set->error_limit)
+                        pr_err("%s: IO error on %s, recovering",
+                               bdevname(ca->bdev, buf), m);
+                else
+                        bch_cache_set_error(ca->set,
+                                            "%s: too many IO errors %s",
+                                            bdevname(ca->bdev, buf), m);
+        }
+}
+
+void bch_bbio_count_io_errors(struct cache_set *c, struct bio *bio,
+                              int error, const char *m)
+{
+        struct bbio *b = container_of(bio, struct bbio, bio);
+        struct cache *ca = PTR_CACHE(c, &b->key, 0);
+
+        unsigned threshold = bio->bi_rw & REQ_WRITE
+                ? c->congested_write_threshold_us
+                : c->congested_read_threshold_us;
+
+        if (threshold) {
+                unsigned t = local_clock_us();
+
+                int us = t - b->submit_time_us;
+                int congested = atomic_read(&c->congested);
+
+                if (us > (int) threshold) {
+                        int ms = us / 1024;
+                        c->congested_last_us = t;
+
+                        ms = min(ms, CONGESTED_MAX + congested);
+                        atomic_sub(ms, &c->congested);
+                } else if (congested < 0)
+                        atomic_inc(&c->congested);
+        }
+
+        bch_count_io_errors(ca, error, m);
+}
+
+void bch_bbio_endio(struct cache_set *c, struct bio *bio,
+                    int error, const char *m)
+{
+        struct closure *cl = bio->bi_private;
+
+        bch_bbio_count_io_errors(c, bio, error, m);
+        bio_put(bio);
+        closure_put(cl);
+}
diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
new file mode 100644
index 000000000000..c871ffaabbb0
--- /dev/null
+++ b/drivers/md/bcache/journal.c
@@ -0,0 +1,785 @@
+/*
+ * bcache journalling code, for btree insertions
+ *
+ * Copyright 2012 Google, Inc.
+ */
+
+#include "bcache.h"
+#include "btree.h"
+#include "debug.h"
+#include "request.h"
+
+/*
+ * Journal replay/recovery:
+ *
+ * This code is all driven from run_cache_set(); we first read the journal
+ * entries, do some other stuff, then we mark all the keys in the journal
+ * entries (same as garbage collection would), then we replay them - reinserting
+ * them into the cache in precisely the same order as they appear in the
+ * journal.
+ *
+ * We only journal keys that go in leaf nodes, which simplifies things quite a
+ * bit.
+ */
+
+static void journal_read_endio(struct bio *bio, int error)
+{
+        struct closure *cl = bio->bi_private;
+        closure_put(cl);
+}
+
+static int journal_read_bucket(struct cache *ca, struct list_head *list,
+                               struct btree_op *op, unsigned bucket_index)
+{
+        struct journal_device *ja = &ca->journal;
+        struct bio *bio = &ja->bio;
+
+        struct journal_replay *i;
+        struct jset *j, *data = ca->set->journal.w[0].data;
+        unsigned len, left, offset = 0;
+        int ret = 0;
+        sector_t bucket = bucket_to_sector(ca->set, ca->sb.d[bucket_index]);
+
+        pr_debug("reading %llu", (uint64_t) bucket);
+
+        while (offset < ca->sb.bucket_size) {
+reread:         left = ca->sb.bucket_size - offset;
+                len = min_t(unsigned, left, PAGE_SECTORS * 8);
+
+                bio_reset(bio);
+                bio->bi_sector  = bucket + offset;
+                bio->bi_bdev    = ca->bdev;
+                bio->bi_rw      = READ;
+                bio->bi_size    = len << 9;
+
+                bio->bi_end_io  = journal_read_endio;
+                bio->bi_private = &op->cl;
+                bio_map(bio, data);
+
+                closure_bio_submit(bio, &op->cl, ca);
+                closure_sync(&op->cl);
+
+                /* This function could be simpler now since we no longer write
+                 * journal entries that overlap bucket boundaries; this means
+                 * the start of a bucket will always have a valid journal entry
+                 * if it has any journal entries at all.
+                 */
+
+                j = data;
+                while (len) {
+                        struct list_head *where;
+                        size_t blocks, bytes = set_bytes(j);
+
+                        if (j->magic != jset_magic(ca->set))
+                                return ret;
+
+                        if (bytes > left << 9)
+                                return ret;
+
+                        if (bytes > len << 9)
+                                goto reread;
+
+                        if (j->csum != csum_set(j))
+                                return ret;
+
+                        blocks = set_blocks(j, ca->set);
+
+                        while (!list_empty(list)) {
+                                i = list_first_entry(list,
+                                        struct journal_replay, list);
+                                if (i->j.seq >= j->last_seq)
+                                        break;
+                                list_del(&i->list);
+                                kfree(i);
+                        }
+
+                        list_for_each_entry_reverse(i, list, list) {
+                                if (j->seq == i->j.seq)
+                                        goto next_set;
+
+                                if (j->seq < i->j.last_seq)
+                                        goto next_set;
+
+                                if (j->seq > i->j.seq) {
+                                        where = &i->list;
+                                        goto add;
+                                }
+                        }
+
+                        where = list;
+add:
+                        i = kmalloc(offsetof(struct journal_replay, j) +
+                                    bytes, GFP_KERNEL);
+                        if (!i)
+                                return -ENOMEM;
+                        memcpy(&i->j, j, bytes);
+                        list_add(&i->list, where);
+                        ret = 1;
+
+                        ja->seq[bucket_index] = j->seq;
+next_set:
+                        offset  += blocks * ca->sb.block_size;
+                        len     -= blocks * ca->sb.block_size;
+                        j = ((void *) j) + blocks * block_bytes(ca);
+                }
+        }
+
+        return ret;
+}
+
+int bch_journal_read(struct cache_set *c, struct list_head *list,
+                        struct btree_op *op)
+{
+#define read_bucket(b)                                                  \
+        ({                                                              \
+                int ret = journal_read_bucket(ca, list, op, b);         \
+                __set_bit(b, bitmap);                                   \
+                if (ret < 0)                                            \
+                        return ret;                                     \
+                ret;                                                    \
+        })
+
+        struct cache *ca;
+        unsigned iter;
+
+        for_each_cache(ca, c, iter) {
+                struct journal_device *ja = &ca->journal;
+                unsigned long bitmap[SB_JOURNAL_BUCKETS / BITS_PER_LONG];
+                unsigned i, l, r, m;
+                uint64_t seq;
+
+                bitmap_zero(bitmap, SB_JOURNAL_BUCKETS);
+                pr_debug("%u journal buckets", ca->sb.njournal_buckets);
+
+                /* Read journal buckets ordered by golden ratio hash to quickly
+                 * find a sequence of buckets with valid journal entries
+                 */
+                for (i = 0; i < ca->sb.njournal_buckets; i++) {
+                        l = (i * 2654435769U) % ca->sb.njournal_buckets;
+
+                        if (test_bit(l, bitmap))
+                                break;
+
+                        if (read_bucket(l))
+                                goto bsearch;
+                }
+
+                /* If that fails, check all the buckets we haven't checked
+                 * already
+                 */
+                pr_debug("falling back to linear search");
+
+                for (l = 0; l < ca->sb.njournal_buckets; l++) {
+                        if (test_bit(l, bitmap))
+                                continue;
+
+                        if (read_bucket(l))
+                                goto bsearch;
+                }
+bsearch:
+                /* Binary search */
+                m = r = find_next_bit(bitmap, ca->sb.njournal_buckets, l + 1);
+                pr_debug("starting binary search, l %u r %u", l, r);
+
+                while (l + 1 < r) {
+                        m = (l + r) >> 1;
+
+                        if (read_bucket(m))
+                                l = m;
+                        else
+                                r = m;
+                }
+
+                /* Read buckets in reverse order until we stop finding more
+                 * journal entries
+                 */
+                pr_debug("finishing up");
+                l = m;
+
+                while (1) {
+                        if (!l--)
+                                l = ca->sb.njournal_buckets - 1;
+
+                        if (l == m)
+                                break;
+
+                        if (test_bit(l, bitmap))
+                                continue;
+
+                        if (!read_bucket(l))
+                                break;
+                }
+
+                seq = 0;
+
+                for (i = 0; i < ca->sb.njournal_buckets; i++)
+                        if (ja->seq[i] > seq) {
+                                seq = ja->seq[i];
+                                ja->cur_idx = ja->discard_idx =
+                                        ja->last_idx = i;
+
+                        }
+        }
+
+        c->journal.seq = list_entry(list->prev,
+                                    struct journal_replay,
+                                    list)->j.seq;
+
+        return 0;
+#undef read_bucket
+}
+
+void bch_journal_mark(struct cache_set *c, struct list_head *list)
+{
+        atomic_t p = { 0 };
+        struct bkey *k;
+        struct journal_replay *i;
+        struct journal *j = &c->journal;
+        uint64_t last = j->seq;
+
+        /*
+         * journal.pin should never fill up - we never write a journal
+         * entry when it would fill up. But if for some reason it does, we
+         * iterate over the list in reverse order so that we can just skip that
+         * refcount instead of bugging.
+         */
+
+        list_for_each_entry_reverse(i, list, list) {
+                BUG_ON(last < i->j.seq);
+                i->pin = NULL;
+
+                while (last-- != i->j.seq)
+                        if (fifo_free(&j->pin) > 1) {
+                                fifo_push_front(&j->pin, p);
+                                atomic_set(&fifo_front(&j->pin), 0);
+                        }
+
+                if (fifo_free(&j->pin) > 1) {
+                        fifo_push_front(&j->pin, p);
+                        i->pin = &fifo_front(&j->pin);
+                        atomic_set(i->pin, 1);
+                }
+
+                for (k = i->j.start;
+                     k < end(&i->j);
+                     k = bkey_next(k)) {
+                        unsigned j;
+
+                        for (j = 0; j < KEY_PTRS(k); j++) {
+                                struct bucket *g = PTR_BUCKET(c, k, j);
+                                atomic_inc(&g->pin);
+
+                                if (g->prio == BTREE_PRIO &&
+                                    !ptr_stale(c, k, j))
+                                        g->prio = INITIAL_PRIO;
+                        }
+
+                        __bch_btree_mark_key(c, 0, k);
+                }
+        }
+}
+
+int bch_journal_replay(struct cache_set *s, struct list_head *list,
+                          struct btree_op *op)
+{
+        int ret = 0, keys = 0, entries = 0;
+        struct bkey *k;
+        struct journal_replay *i =
+                list_entry(list->prev, struct journal_replay, list);
+
+        uint64_t start = i->j.last_seq, end = i->j.seq, n = start;
+
+        list_for_each_entry(i, list, list) {
+                BUG_ON(i->pin && atomic_read(i->pin) != 1);
+
+                if (n != i->j.seq)
+                        pr_err("journal entries %llu-%llu "
+                               "missing! (replaying %llu-%llu)\n",
+                               n, i->j.seq - 1, start, end);
+
+                for (k = i->j.start;
+                     k < end(&i->j);
+                     k = bkey_next(k)) {
+                        pr_debug("%s", pkey(k));
+                        bkey_copy(op->keys.top, k);
+                        bch_keylist_push(&op->keys);
+
+                        op->journal = i->pin;
+                        atomic_inc(op->journal);
+
+                        ret = bch_btree_insert(op, s);
+                        if (ret)
+                                goto err;
+
+                        BUG_ON(!bch_keylist_empty(&op->keys));
+                        keys++;
+
+                        cond_resched();
+                }
+
+                if (i->pin)
+                        atomic_dec(i->pin);
+                n = i->j.seq + 1;
+                entries++;
+        }
+
+        pr_info("journal replay done, %i keys in %i entries, seq %llu",
+                keys, entries, end);
+
+        while (!list_empty(list)) {
+                i = list_first_entry(list, struct journal_replay, list);
+                list_del(&i->list);
+                kfree(i);
+        }
+err:
+        closure_sync(&op->cl);
+        return ret;
+}
+
+/* Journalling */
+
+static void btree_flush_write(struct cache_set *c)
+{
+        /*
+         * Try to find the btree node with that references the oldest journal
+         * entry, best is our current candidate and is locked if non NULL:
+         */
+        struct btree *b, *best = NULL;
+        unsigned iter;
+
+        for_each_cached_btree(b, c, iter) {
+                if (!down_write_trylock(&b->lock))
+                        continue;
+
+                if (!btree_node_dirty(b) ||
+                    !btree_current_write(b)->journal) {
+                        rw_unlock(true, b);
+                        continue;
+                }
+
+                if (!best)
+                        best = b;
+                else if (journal_pin_cmp(c,
+                                         btree_current_write(best),
+                                         btree_current_write(b))) {
+                        rw_unlock(true, best);
+                        best = b;
+                } else
+                        rw_unlock(true, b);
+        }
+
+        if (best)
+                goto out;
+
+        /* We can't find the best btree node, just pick the first */
+        list_for_each_entry(b, &c->btree_cache, list)
+                if (!b->level && btree_node_dirty(b)) {
+                        best = b;
+                        rw_lock(true, best, best->level);
+                        goto found;
+                }
+
+out:
+        if (!best)
+                return;
+found:
+        if (btree_node_dirty(best))
+                bch_btree_write(best, true, NULL);
+        rw_unlock(true, best);
+}
+
+#define last_seq(j)     ((j)->seq - fifo_used(&(j)->pin) + 1)
+
+static void journal_discard_endio(struct bio *bio, int error)
+{
+        struct journal_device *ja =
+                container_of(bio, struct journal_device, discard_bio);
+        struct cache *ca = container_of(ja, struct cache, journal);
+
+        atomic_set(&ja->discard_in_flight, DISCARD_DONE);
+
+        closure_wake_up(&ca->set->journal.wait);
+        closure_put(&ca->set->cl);
+}
+
+static void journal_discard_work(struct work_struct *work)
+{
+        struct journal_device *ja =
+                container_of(work, struct journal_device, discard_work);
+
+        submit_bio(0, &ja->discard_bio);
+}
+
+static void do_journal_discard(struct cache *ca)
+{
+        struct journal_device *ja = &ca->journal;
+        struct bio *bio = &ja->discard_bio;
+
+        if (!ca->discard) {
+                ja->discard_idx = ja->last_idx;
+                return;
+        }
+
+        switch (atomic_read(&ja->discard_in_flight) == DISCARD_IN_FLIGHT) {
+        case DISCARD_IN_FLIGHT:
+                return;
+
+        case DISCARD_DONE:
+                ja->discard_idx = (ja->discard_idx + 1) %
+                        ca->sb.njournal_buckets;
+
+                atomic_set(&ja->discard_in_flight, DISCARD_READY);
+                /* fallthrough */
+
+        case DISCARD_READY:
+                if (ja->discard_idx == ja->last_idx)
+                        return;
+
+                atomic_set(&ja->discard_in_flight, DISCARD_IN_FLIGHT);
+
+                bio_init(bio);
+                bio->bi_sector          = bucket_to_sector(ca->set,
+                                                           ca->sb.d[ja->discard_idx]);
+                bio->bi_bdev            = ca->bdev;
+                bio->bi_rw              = REQ_WRITE|REQ_DISCARD;
+                bio->bi_max_vecs        = 1;
+                bio->bi_io_vec          = bio->bi_inline_vecs;
+                bio->bi_size            = bucket_bytes(ca);
+                bio->bi_end_io          = journal_discard_endio;
+
+                closure_get(&ca->set->cl);
+                INIT_WORK(&ja->discard_work, journal_discard_work);
+                schedule_work(&ja->discard_work);
+        }
+}
+
+static void journal_reclaim(struct cache_set *c)
+{
+        struct bkey *k = &c->journal.key;
+        struct cache *ca;
+        uint64_t last_seq;
+        unsigned iter, n = 0;
+        atomic_t p;
+
+        while (!atomic_read(&fifo_front(&c->journal.pin)))
+                fifo_pop(&c->journal.pin, p);
+
+        last_seq = last_seq(&c->journal);
+
+        /* Update last_idx */
+
+        for_each_cache(ca, c, iter) {
+                struct journal_device *ja = &ca->journal;
+
+                while (ja->last_idx != ja->cur_idx &&
+                       ja->seq[ja->last_idx] < last_seq)
+                        ja->last_idx = (ja->last_idx + 1) %
+                                ca->sb.njournal_buckets;
+        }
+
+        for_each_cache(ca, c, iter)
+                do_journal_discard(ca);
+
+        if (c->journal.blocks_free)
+                return;
+
+        /*
+         * Allocate:
+         * XXX: Sort by free journal space
+         */
+
+        for_each_cache(ca, c, iter) {
+                struct journal_device *ja = &ca->journal;
+                unsigned next = (ja->cur_idx + 1) % ca->sb.njournal_buckets;
+
+                /* No space available on this device */
+                if (next == ja->discard_idx)
+                        continue;
+
+                ja->cur_idx = next;
+                k->ptr[n++] = PTR(0,
+                                  bucket_to_sector(c, ca->sb.d[ja->cur_idx]),
+                                  ca->sb.nr_this_dev);
+        }
+
+        bkey_init(k);
+        SET_KEY_PTRS(k, n);
+
+        if (n)
+                c->journal.blocks_free = c->sb.bucket_size >> c->block_bits;
+
+        if (!journal_full(&c->journal))
+                __closure_wake_up(&c->journal.wait);
+}
+
+void bch_journal_next(struct journal *j)
+{
+        atomic_t p = { 1 };
+
+        j->cur = (j->cur == j->w)
+                ? &j->w[1]
+                : &j->w[0];
+
+        /*
+         * The fifo_push() needs to happen at the same time as j->seq is
+         * incremented for last_seq() to be calculated correctly
+         */
+        BUG_ON(!fifo_push(&j->pin, p));
+        atomic_set(&fifo_back(&j->pin), 1);
+
+        j->cur->data->seq       = ++j->seq;
+        j->cur->need_write      = false;
+        j->cur->data->keys      = 0;
+
+        if (fifo_full(&j->pin))
+                pr_debug("journal_pin full (%zu)", fifo_used(&j->pin));
+}
+
+static void journal_write_endio(struct bio *bio, int error)
+{
+        struct journal_write *w = bio->bi_private;
+
+        cache_set_err_on(error, w->c, "journal io error");
+        closure_put(&w->c->journal.io.cl);
+}
+
+static void journal_write(struct closure *);
+
+static void journal_write_done(struct closure *cl)
+{
+        struct journal *j = container_of(cl, struct journal, io.cl);
+        struct cache_set *c = container_of(j, struct cache_set, journal);
+
+        struct journal_write *w = (j->cur == j->w)
+                ? &j->w[1]
+                : &j->w[0];
+
+        __closure_wake_up(&w->wait);
+
+        if (c->journal_delay_ms)
+                closure_delay(&j->io, msecs_to_jiffies(c->journal_delay_ms));
+
+        continue_at(cl, journal_write, system_wq);
+}
+
+static void journal_write_unlocked(struct closure *cl)
+{
+        struct cache_set *c = container_of(cl, struct cache_set, journal.io.cl);
+        struct cache *ca;
+        struct journal_write *w = c->journal.cur;
+        struct bkey *k = &c->journal.key;
+        unsigned i, sectors = set_blocks(w->data, c) * c->sb.block_size;
+
+        struct bio *bio;
+        struct bio_list list;
+        bio_list_init(&list);
+
+        if (!w->need_write) {
+                /*
+                 * XXX: have to unlock closure before we unlock journal lock,
+                 * else we race with bch_journal(). But this way we race
+                 * against cache set unregister. Doh.
+                 */
+                set_closure_fn(cl, NULL, NULL);
+                closure_sub(cl, CLOSURE_RUNNING + 1);
+                spin_unlock(&c->journal.lock);
+                return;
+        } else if (journal_full(&c->journal)) {
+                journal_reclaim(c);
+                spin_unlock(&c->journal.lock);
+
+                btree_flush_write(c);
+                continue_at(cl, journal_write, system_wq);
+        }
+
+        c->journal.blocks_free -= set_blocks(w->data, c);
+
+        w->data->btree_level = c->root->level;
+
+        bkey_copy(&w->data->btree_root, &c->root->key);
+        bkey_copy(&w->data->uuid_bucket, &c->uuid_bucket);
+
+        for_each_cache(ca, c, i)
+                w->data->prio_bucket[ca->sb.nr_this_dev] = ca->prio_buckets[0];
+
+        w->data->magic          = jset_magic(c);
+        w->data->version        = BCACHE_JSET_VERSION;
+        w->data->last_seq       = last_seq(&c->journal);
+        w->data->csum           = csum_set(w->data);
+
+        for (i = 0; i < KEY_PTRS(k); i++) {
+                ca = PTR_CACHE(c, k, i);
+                bio = &ca->journal.bio;
+
+                atomic_long_add(sectors, &ca->meta_sectors_written);
+
+                bio_reset(bio);
+                bio->bi_sector  = PTR_OFFSET(k, i);
+                bio->bi_bdev    = ca->bdev;
+                bio->bi_rw      = REQ_WRITE|REQ_SYNC|REQ_META|REQ_FLUSH;
+                bio->bi_size    = sectors << 9;
+
+                bio->bi_end_io  = journal_write_endio;
+                bio->bi_private = w;
+                bio_map(bio, w->data);
+
+                trace_bcache_journal_write(bio);
+                bio_list_add(&list, bio);
+
+                SET_PTR_OFFSET(k, i, PTR_OFFSET(k, i) + sectors);
+
+                ca->journal.seq[ca->journal.cur_idx] = w->data->seq;
+        }
+
+        atomic_dec_bug(&fifo_back(&c->journal.pin));
+        bch_journal_next(&c->journal);
+        journal_reclaim(c);
+
+        spin_unlock(&c->journal.lock);
+
+        while ((bio = bio_list_pop(&list)))
+                closure_bio_submit(bio, cl, c->cache[0]);
+
+        continue_at(cl, journal_write_done, NULL);
+}
+
+static void journal_write(struct closure *cl)
+{
+        struct cache_set *c = container_of(cl, struct cache_set, journal.io.cl);
+
+        spin_lock(&c->journal.lock);
+        journal_write_unlocked(cl);
+}
+
+static void __journal_try_write(struct cache_set *c, bool noflush)
+{
+        struct closure *cl = &c->journal.io.cl;
+
+        if (!closure_trylock(cl, &c->cl))
+                spin_unlock(&c->journal.lock);
+        else if (noflush && journal_full(&c->journal)) {
+                spin_unlock(&c->journal.lock);
+                continue_at(cl, journal_write, system_wq);
+        } else
+                journal_write_unlocked(cl);
+}
+
+#define journal_try_write(c)    __journal_try_write(c, false)
+
+void bch_journal_meta(struct cache_set *c, struct closure *cl)
+{
+        struct journal_write *w;
+
+        if (CACHE_SYNC(&c->sb)) {
+                spin_lock(&c->journal.lock);
+
+                w = c->journal.cur;
+                w->need_write = true;
+
+                if (cl)
+                        BUG_ON(!closure_wait(&w->wait, cl));
+
+                __journal_try_write(c, true);
+        }
+}
+
+/*
+ * Entry point to the journalling code - bio_insert() and btree_invalidate()
+ * pass bch_journal() a list of keys to be journalled, and then
+ * bch_journal() hands those same keys off to btree_insert_async()
+ */
+
+void bch_journal(struct closure *cl)
+{
+        struct btree_op *op = container_of(cl, struct btree_op, cl);
+        struct cache_set *c = op->c;
+        struct journal_write *w;
+        size_t b, n = ((uint64_t *) op->keys.top) - op->keys.list;
+
+        if (op->type != BTREE_INSERT ||
+            !CACHE_SYNC(&c->sb))
+                goto out;
+
+        /*
+         * If we're looping because we errored, might already be waiting on
+         * another journal write:
+         */
+        while (atomic_read(&cl->parent->remaining) & CLOSURE_WAITING)
+                closure_sync(cl->parent);
+
+        spin_lock(&c->journal.lock);
+
+        if (journal_full(&c->journal)) {
+                /* XXX: tracepoint */
+                closure_wait(&c->journal.wait, cl);
+
+                journal_reclaim(c);
+                spin_unlock(&c->journal.lock);
+
+                btree_flush_write(c);
+                continue_at(cl, bch_journal, bcache_wq);
+        }
+
+        w = c->journal.cur;
+        w->need_write = true;
+        b = __set_blocks(w->data, w->data->keys + n, c);
+
+        if (b * c->sb.block_size > PAGE_SECTORS << JSET_BITS ||
+            b > c->journal.blocks_free) {
+                /* XXX: If we were inserting so many keys that they won't fit in
+                 * an _empty_ journal write, we'll deadlock. For now, handle
+                 * this in bch_keylist_realloc() - but something to think about.
+                 */
+                BUG_ON(!w->data->keys);
+
+                /* XXX: tracepoint */
+                BUG_ON(!closure_wait(&w->wait, cl));
+
+                closure_flush(&c->journal.io);
+
+                journal_try_write(c);
+                continue_at(cl, bch_journal, bcache_wq);
+        }
+
+        memcpy(end(w->data), op->keys.list, n * sizeof(uint64_t));
+        w->data->keys += n;
+
+        op->journal = &fifo_back(&c->journal.pin);
+        atomic_inc(op->journal);
+
+        if (op->flush_journal) {
+                closure_flush(&c->journal.io);
+                closure_wait(&w->wait, cl->parent);
+        }
+
+        journal_try_write(c);
+out:
+        bch_btree_insert_async(cl);
+}
+
+void bch_journal_free(struct cache_set *c)
+{
+        free_pages((unsigned long) c->journal.w[1].data, JSET_BITS);
+        free_pages((unsigned long) c->journal.w[0].data, JSET_BITS);
+        free_fifo(&c->journal.pin);
+}
+
+int bch_journal_alloc(struct cache_set *c)
+{
+        struct journal *j = &c->journal;
+
+        closure_init_unlocked(&j->io);
+        spin_lock_init(&j->lock);
+
+        c->journal_delay_ms = 100;
+
+        j->w[0].c = c;
+        j->w[1].c = c;
+
+        if (!(init_fifo(&j->pin, JOURNAL_PIN, GFP_KERNEL)) ||
+            !(j->w[0].data = (void *) __get_free_pages(GFP_KERNEL, JSET_BITS)) ||
+            !(j->w[1].data = (void *) __get_free_pages(GFP_KERNEL, JSET_BITS)))
+                return -ENOMEM;
+
+        return 0;
+}
diff --git a/drivers/md/bcache/journal.h b/drivers/md/bcache/journal.h
new file mode 100644
index 000000000000..3d7851274b04
--- /dev/null
+++ b/drivers/md/bcache/journal.h
@@ -0,0 +1,215 @@
+#ifndef _BCACHE_JOURNAL_H
+#define _BCACHE_JOURNAL_H
+
+/*
+ * THE JOURNAL:
+ *
+ * The journal is treated as a circular buffer of buckets - a journal entry
+ * never spans two buckets. This means (not implemented yet) we can resize the
+ * journal at runtime, and will be needed for bcache on raw flash support.
+ *
+ * Journal entries contain a list of keys, ordered by the time they were
+ * inserted; thus journal replay just has to reinsert the keys.
+ *
+ * We also keep some things in the journal header that are logically part of the
+ * superblock - all the things that are frequently updated. This is for future
+ * bcache on raw flash support; the superblock (which will become another
+ * journal) can't be moved or wear leveled, so it contains just enough
+ * information to find the main journal, and the superblock only has to be
+ * rewritten when we want to move/wear level the main journal.
+ *
+ * Currently, we don't journal BTREE_REPLACE operations - this will hopefully be
+ * fixed eventually. This isn't a bug - BTREE_REPLACE is used for insertions
+ * from cache misses, which don't have to be journaled, and for writeback and
+ * moving gc we work around it by flushing the btree to disk before updating the
+ * gc information. But it is a potential issue with incremental garbage
+ * collection, and it's fragile.
+ *
+ * OPEN JOURNAL ENTRIES:
+ *
+ * Each journal entry contains, in the header, the sequence number of the last
+ * journal entry still open - i.e. that has keys that haven't been flushed to
+ * disk in the btree.
+ *
+ * We track this by maintaining a refcount for every open journal entry, in a
+ * fifo; each entry in the fifo corresponds to a particular journal
+ * entry/sequence number. When the refcount at the tail of the fifo goes to
+ * zero, we pop it off - thus, the size of the fifo tells us the number of open
+ * journal entries
+ *
+ * We take a refcount on a journal entry when we add some keys to a journal
+ * entry that we're going to insert (held by struct btree_op), and then when we
+ * insert those keys into the btree the btree write we're setting up takes a
+ * copy of that refcount (held by struct btree_write). That refcount is dropped
+ * when the btree write completes.
+ *
+ * A struct btree_write can only hold a refcount on a single journal entry, but
+ * might contain keys for many journal entries - we handle this by making sure
+ * it always has a refcount on the _oldest_ journal entry of all the journal
+ * entries it has keys for.
+ *
+ * JOURNAL RECLAIM:
+ *
+ * As mentioned previously, our fifo of refcounts tells us the number of open
+ * journal entries; from that and the current journal sequence number we compute
+ * last_seq - the oldest journal entry we still need. We write last_seq in each
+ * journal entry, and we also have to keep track of where it exists on disk so
+ * we don't overwrite it when we loop around the journal.
+ *
+ * To do that we track, for each journal bucket, the sequence number of the
+ * newest journal entry it contains - if we don't need that journal entry we
+ * don't need anything in that bucket anymore. From that we track the last
+ * journal bucket we still need; all this is tracked in struct journal_device
+ * and updated by journal_reclaim().
+ *
+ * JOURNAL FILLING UP:
+ *
+ * There are two ways the journal could fill up; either we could run out of
+ * space to write to, or we could have too many open journal entries and run out
+ * of room in the fifo of refcounts. Since those refcounts are decremented
+ * without any locking we can't safely resize that fifo, so we handle it the
+ * same way.
+ *
+ * If the journal fills up, we start flushing dirty btree nodes until we can
+ * allocate space for a journal write again - preferentially flushing btree
+ * nodes that are pinning the oldest journal entries first.
+ */
+
+#define BCACHE_JSET_VERSION_UUIDv1      1
+/* Always latest UUID format */
+#define BCACHE_JSET_VERSION_UUID        1
+#define BCACHE_JSET_VERSION             1
+
+/*
+ * On disk format for a journal entry:
+ * seq is monotonically increasing; every journal entry has its own unique
+ * sequence number.
+ *
+ * last_seq is the oldest journal entry that still has keys the btree hasn't
+ * flushed to disk yet.
+ *
+ * version is for on disk format changes.
+ */
+struct jset {
+        uint64_t                csum;
+        uint64_t                magic;
+        uint64_t                seq;
+        uint32_t                version;
+        uint32_t                keys;
+
+        uint64_t                last_seq;
+
+        BKEY_PADDED(uuid_bucket);
+        BKEY_PADDED(btree_root);
+        uint16_t                btree_level;
+        uint16_t                pad[3];
+
+        uint64_t                prio_bucket[MAX_CACHES_PER_SET];
+
+        union {
+                struct bkey     start[0];
+                uint64_t        d[0];
+        };
+};
+
+/*
+ * Only used for holding the journal entries we read in btree_journal_read()
+ * during cache_registration
+ */
+struct journal_replay {
+        struct list_head        list;
+        atomic_t                *pin;
+        struct jset             j;
+};
+
+/*
+ * We put two of these in struct journal; we used them for writes to the
+ * journal that are being staged or in flight.
+ */
+struct journal_write {
+        struct jset             *data;
+#define JSET_BITS               3
+
+        struct cache_set        *c;
+        struct closure_waitlist wait;
+        bool                    need_write;
+};
+
+/* Embedded in struct cache_set */
+struct journal {
+        spinlock_t              lock;
+        /* used when waiting because the journal was full */
+        struct closure_waitlist wait;
+        struct closure_with_timer io;
+
+        /* Number of blocks free in the bucket(s) we're currently writing to */
+        unsigned                blocks_free;
+        uint64_t                seq;
+        DECLARE_FIFO(atomic_t, pin);
+
+        BKEY_PADDED(key);
+
+        struct journal_write    w[2], *cur;
+};
+
+/*
+ * Embedded in struct cache. First three fields refer to the array of journal
+ * buckets, in cache_sb.
+ */
+struct journal_device {
+        /*
+         * For each journal bucket, contains the max sequence number of the
+         * journal writes it contains - so we know when a bucket can be reused.
+         */
+        uint64_t                seq[SB_JOURNAL_BUCKETS];
+
+        /* Journal bucket we're currently writing to */
+        unsigned                cur_idx;
+
+        /* Last journal bucket that still contains an open journal entry */
+        unsigned                last_idx;
+
+        /* Next journal bucket to be discarded */
+        unsigned                discard_idx;
+
+#define DISCARD_READY           0
+#define DISCARD_IN_FLIGHT       1
+#define DISCARD_DONE            2
+        /* 1 - discard in flight, -1 - discard completed */
+        atomic_t                discard_in_flight;
+
+        struct work_struct      discard_work;
+        struct bio              discard_bio;
+        struct bio_vec          discard_bv;
+
+        /* Bio for journal reads/writes to this device */
+        struct bio              bio;
+        struct bio_vec          bv[8];
+};
+
+#define journal_pin_cmp(c, l, r)                                \
+        (fifo_idx(&(c)->journal.pin, (l)->journal) >            \
+         fifo_idx(&(c)->journal.pin, (r)->journal))
+
+#define JOURNAL_PIN     20000
+
+#define journal_full(j)                                         \
+        (!(j)->blocks_free || fifo_free(&(j)->pin) <= 1)
+
+struct closure;
+struct cache_set;
+struct btree_op;
+
+void bch_journal(struct closure *);
+void bch_journal_next(struct journal *);
+void bch_journal_mark(struct cache_set *, struct list_head *);
+void bch_journal_meta(struct cache_set *, struct closure *);
+int bch_journal_read(struct cache_set *, struct list_head *,
+                        struct btree_op *);
+int bch_journal_replay(struct cache_set *, struct list_head *,
+                          struct btree_op *);
+
+void bch_journal_free(struct cache_set *);
+int bch_journal_alloc(struct cache_set *);
+
+#endif /* _BCACHE_JOURNAL_H */
diff --git a/drivers/md/bcache/movinggc.c b/drivers/md/bcache/movinggc.c
new file mode 100644
index 000000000000..c69fc92b02cf
--- /dev/null
+++ b/drivers/md/bcache/movinggc.c
@@ -0,0 +1,254 @@
+/*
+ * Moving/copying garbage collector
+ *
+ * Copyright 2012 Google, Inc.
+ */
+
+#include "bcache.h"
+#include "btree.h"
+#include "debug.h"
+#include "request.h"
+
+struct moving_io {
+        struct keybuf_key       *w;
+        struct search           s;
+        struct bbio             bio;
+};
+
+static bool moving_pred(struct keybuf *buf, struct bkey *k)
+{
+        struct cache_set *c = container_of(buf, struct cache_set,
+                                           moving_gc_keys);
+        unsigned i;
+
+        for (i = 0; i < KEY_PTRS(k); i++) {
+                struct cache *ca = PTR_CACHE(c, k, i);
+                struct bucket *g = PTR_BUCKET(c, k, i);
+
+                if (GC_SECTORS_USED(g) < ca->gc_move_threshold)
+                        return true;
+        }
+
+        return false;
+}
+
+/* Moving GC - IO loop */
+
+static void moving_io_destructor(struct closure *cl)
+{
+        struct moving_io *io = container_of(cl, struct moving_io, s.cl);
+        kfree(io);
+}
+
+static void write_moving_finish(struct closure *cl)
+{
+        struct moving_io *io = container_of(cl, struct moving_io, s.cl);
+        struct bio *bio = &io->bio.bio;
+        struct bio_vec *bv = bio_iovec_idx(bio, bio->bi_vcnt);
+
+        while (bv-- != bio->bi_io_vec)
+                __free_page(bv->bv_page);
+
+        pr_debug("%s %s", io->s.op.insert_collision
+                 ? "collision moving" : "moved",
+                 pkey(&io->w->key));
+
+        bch_keybuf_del(&io->s.op.c->moving_gc_keys, io->w);
+
+        atomic_dec_bug(&io->s.op.c->in_flight);
+        closure_wake_up(&io->s.op.c->moving_gc_wait);
+
+        closure_return_with_destructor(cl, moving_io_destructor);
+}
+
+static void read_moving_endio(struct bio *bio, int error)
+{
+        struct moving_io *io = container_of(bio->bi_private,
+                                            struct moving_io, s.cl);
+
+        if (error)
+                io->s.error = error;
+
+        bch_bbio_endio(io->s.op.c, bio, error, "reading data to move");
+}
+
+static void moving_init(struct moving_io *io)
+{
+        struct bio *bio = &io->bio.bio;
+
+        bio_init(bio);
+        bio_get(bio);
+        bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
+
+        bio->bi_size            = KEY_SIZE(&io->w->key) << 9;
+        bio->bi_max_vecs        = DIV_ROUND_UP(KEY_SIZE(&io->w->key),
+                                               PAGE_SECTORS);
+        bio->bi_private         = &io->s.cl;
+        bio->bi_io_vec          = bio->bi_inline_vecs;
+        bio_map(bio, NULL);
+}
+
+static void write_moving(struct closure *cl)
+{
+        struct search *s = container_of(cl, struct search, cl);
+        struct moving_io *io = container_of(s, struct moving_io, s);
+
+        if (!s->error) {
+                trace_bcache_write_moving(&io->bio.bio);
+
+                moving_init(io);
+
+                io->bio.bio.bi_sector   = KEY_START(&io->w->key);
+                s->op.lock              = -1;
+                s->op.write_prio        = 1;
+                s->op.cache_bio         = &io->bio.bio;
+
+                s->writeback            = KEY_DIRTY(&io->w->key);
+                s->op.csum              = KEY_CSUM(&io->w->key);
+
+                s->op.type = BTREE_REPLACE;
+                bkey_copy(&s->op.replace, &io->w->key);
+
+                closure_init(&s->op.cl, cl);
+                bch_insert_data(&s->op.cl);
+        }
+
+        continue_at(cl, write_moving_finish, NULL);
+}
+
+static void read_moving_submit(struct closure *cl)
+{
+        struct search *s = container_of(cl, struct search, cl);
+        struct moving_io *io = container_of(s, struct moving_io, s);
+        struct bio *bio = &io->bio.bio;
+
+        trace_bcache_read_moving(bio);
+        bch_submit_bbio(bio, s->op.c, &io->w->key, 0);
+
+        continue_at(cl, write_moving, bch_gc_wq);
+}
+
+static void read_moving(struct closure *cl)
+{
+        struct cache_set *c = container_of(cl, struct cache_set, moving_gc);
+        struct keybuf_key *w;
+        struct moving_io *io;
+        struct bio *bio;
+
+        /* XXX: if we error, background writeback could stall indefinitely */
+
+        while (!test_bit(CACHE_SET_STOPPING, &c->flags)) {
+                w = bch_keybuf_next_rescan(c, &c->moving_gc_keys, &MAX_KEY);
+                if (!w)
+                        break;
+
+                io = kzalloc(sizeof(struct moving_io) + sizeof(struct bio_vec)
+                             * DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS),
+                             GFP_KERNEL);
+                if (!io)
+                        goto err;
+
+                w->private      = io;
+                io->w           = w;
+                io->s.op.inode  = KEY_INODE(&w->key);
+                io->s.op.c      = c;
+
+                moving_init(io);
+                bio = &io->bio.bio;
+
+                bio->bi_rw      = READ;
+                bio->bi_end_io  = read_moving_endio;
+
+                if (bio_alloc_pages(bio, GFP_KERNEL))
+                        goto err;
+
+                pr_debug("%s", pkey(&w->key));
+
+                closure_call(&io->s.cl, read_moving_submit, NULL, &c->gc.cl);
+
+                if (atomic_inc_return(&c->in_flight) >= 64) {
+                        closure_wait_event(&c->moving_gc_wait, cl,
+                                           atomic_read(&c->in_flight) < 64);
+                        continue_at(cl, read_moving, bch_gc_wq);
+                }
+        }
+
+        if (0) {
+err:            if (!IS_ERR_OR_NULL(w->private))
+                        kfree(w->private);
+
+                bch_keybuf_del(&c->moving_gc_keys, w);
+        }
+
+        closure_return(cl);
+}
+
+void bch_moving_gc(struct closure *cl)
+{
+        struct cache_set *c = container_of(cl, struct cache_set, gc.cl);
+        struct cache *ca;
+        struct bucket *b;
+        unsigned i;
+
+        bool bucket_cmp(struct bucket *l, struct bucket *r)
+        {
+                return GC_SECTORS_USED(l) < GC_SECTORS_USED(r);
+        }
+
+        unsigned top(struct cache *ca)
+        {
+                return GC_SECTORS_USED(heap_peek(&ca->heap));
+        }
+
+        if (!c->copy_gc_enabled)
+                closure_return(cl);
+
+        mutex_lock(&c->bucket_lock);
+
+        for_each_cache(ca, c, i) {
+                unsigned sectors_to_move = 0;
+                unsigned reserve_sectors = ca->sb.bucket_size *
+                        min(fifo_used(&ca->free), ca->free.size / 2);
+
+                ca->heap.used = 0;
+
+                for_each_bucket(b, ca) {
+                        if (!GC_SECTORS_USED(b))
+                                continue;
+
+                        if (!heap_full(&ca->heap)) {
+                                sectors_to_move += GC_SECTORS_USED(b);
+                                heap_add(&ca->heap, b, bucket_cmp);
+                        } else if (bucket_cmp(b, heap_peek(&ca->heap))) {
+                                sectors_to_move -= top(ca);
+                                sectors_to_move += GC_SECTORS_USED(b);
+
+                                ca->heap.data[0] = b;
+                                heap_sift(&ca->heap, 0, bucket_cmp);
+                        }
+                }
+
+                while (sectors_to_move > reserve_sectors) {
+                        heap_pop(&ca->heap, b, bucket_cmp);
+                        sectors_to_move -= GC_SECTORS_USED(b);
+                }
+
+                ca->gc_move_threshold = top(ca);
+
+                pr_debug("threshold %u", ca->gc_move_threshold);
+        }
+
+        mutex_unlock(&c->bucket_lock);
+
+        c->moving_gc_keys.last_scanned = ZERO_KEY;
+
+        closure_init(&c->moving_gc, cl);
+        read_moving(&c->moving_gc);
+
+        closure_return(cl);
+}
+
+void bch_moving_init_cache_set(struct cache_set *c)
+{
+        bch_keybuf_init(&c->moving_gc_keys, moving_pred);
+}
diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
new file mode 100644
index 000000000000..4f552de49aaa
--- /dev/null
+++ b/drivers/md/bcache/request.c
@@ -0,0 +1,1409 @@
+/*
+ * Main bcache entry point - handle a read or a write request and decide what to
+ * do with it; the make_request functions are called by the block layer.
+ *
+ * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
+ * Copyright 2012 Google, Inc.
+ */
+
+#include "bcache.h"
+#include "btree.h"
+#include "debug.h"
+#include "request.h"
+
+#include <linux/cgroup.h>
+#include <linux/module.h>
+#include <linux/hash.h>
+#include <linux/random.h>
+#include "blk-cgroup.h"
+
+#include <trace/events/bcache.h>
+
+#define CUTOFF_CACHE_ADD        95
+#define CUTOFF_CACHE_READA      90
+#define CUTOFF_WRITEBACK        50
+#define CUTOFF_WRITEBACK_SYNC   75
+
+struct kmem_cache *bch_search_cache;
+
+static void check_should_skip(struct cached_dev *, struct search *);
+
+/* Cgroup interface */
+
+#ifdef CONFIG_CGROUP_BCACHE
+static struct bch_cgroup bcache_default_cgroup = { .cache_mode = -1 };
+
+static struct bch_cgroup *cgroup_to_bcache(struct cgroup *cgroup)
+{
+        struct cgroup_subsys_state *css;
+        return cgroup &&
+                (css = cgroup_subsys_state(cgroup, bcache_subsys_id))
+                ? container_of(css, struct bch_cgroup, css)
+                : &bcache_default_cgroup;
+}
+
+struct bch_cgroup *bch_bio_to_cgroup(struct bio *bio)
+{
+        struct cgroup_subsys_state *css = bio->bi_css
+                ? cgroup_subsys_state(bio->bi_css->cgroup, bcache_subsys_id)
+                : task_subsys_state(current, bcache_subsys_id);
+
+        return css
+                ? container_of(css, struct bch_cgroup, css)
+                : &bcache_default_cgroup;
+}
+
+static ssize_t cache_mode_read(struct cgroup *cgrp, struct cftype *cft,
+                        struct file *file,
+                        char __user *buf, size_t nbytes, loff_t *ppos)
+{
+        char tmp[1024];
+        int len = snprint_string_list(tmp, PAGE_SIZE, bch_cache_modes,
+                                      cgroup_to_bcache(cgrp)->cache_mode + 1);
+
+        if (len < 0)
+                return len;
+
+        return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
+}
+
+static int cache_mode_write(struct cgroup *cgrp, struct cftype *cft,
+                            const char *buf)
+{
+        int v = read_string_list(buf, bch_cache_modes);
+        if (v < 0)
+                return v;
+
+        cgroup_to_bcache(cgrp)->cache_mode = v - 1;
+        return 0;
+}
+
+static u64 bch_verify_read(struct cgroup *cgrp, struct cftype *cft)
+{
+        return cgroup_to_bcache(cgrp)->verify;
+}
+
+static int bch_verify_write(struct cgroup *cgrp, struct cftype *cft, u64 val)
+{
+        cgroup_to_bcache(cgrp)->verify = val;
+        return 0;
+}
+
+static u64 bch_cache_hits_read(struct cgroup *cgrp, struct cftype *cft)
+{
+        struct bch_cgroup *bcachecg = cgroup_to_bcache(cgrp);
+        return atomic_read(&bcachecg->stats.cache_hits);
+}
+
+static u64 bch_cache_misses_read(struct cgroup *cgrp, struct cftype *cft)
+{
+        struct bch_cgroup *bcachecg = cgroup_to_bcache(cgrp);
+        return atomic_read(&bcachecg->stats.cache_misses);
+}
+
+static u64 bch_cache_bypass_hits_read(struct cgroup *cgrp,
+                                         struct cftype *cft)
+{
+        struct bch_cgroup *bcachecg = cgroup_to_bcache(cgrp);
+        return atomic_read(&bcachecg->stats.cache_bypass_hits);
+}
+
+static u64 bch_cache_bypass_misses_read(struct cgroup *cgrp,
+                                           struct cftype *cft)
+{
+        struct bch_cgroup *bcachecg = cgroup_to_bcache(cgrp);
+        return atomic_read(&bcachecg->stats.cache_bypass_misses);
+}
+
+static struct cftype bch_files[] = {
+        {
+                .name           = "cache_mode",
+                .read           = cache_mode_read,
+                .write_string   = cache_mode_write,
+        },
+        {
+                .name           = "verify",
+                .read_u64       = bch_verify_read,
+                .write_u64      = bch_verify_write,
+        },
+        {
+                .name           = "cache_hits",
+                .read_u64       = bch_cache_hits_read,
+        },
+        {
+                .name           = "cache_misses",
+                .read_u64       = bch_cache_misses_read,
+        },
+        {
+                .name           = "cache_bypass_hits",
+                .read_u64       = bch_cache_bypass_hits_read,
+        },
+        {
+                .name           = "cache_bypass_misses",
+                .read_u64       = bch_cache_bypass_misses_read,
+        },
+        { }     /* terminate */
+};
+
+static void init_bch_cgroup(struct bch_cgroup *cg)
+{
+        cg->cache_mode = -1;
+}
+
+static struct cgroup_subsys_state *bcachecg_create(struct cgroup *cgroup)
+{
+        struct bch_cgroup *cg;
+
+        cg = kzalloc(sizeof(*cg), GFP_KERNEL);
+        if (!cg)
+                return ERR_PTR(-ENOMEM);
+        init_bch_cgroup(cg);
+        return &cg->css;
+}
+
+static void bcachecg_destroy(struct cgroup *cgroup)
+{
+        struct bch_cgroup *cg = cgroup_to_bcache(cgroup);
+        free_css_id(&bcache_subsys, &cg->css);
+        kfree(cg);
+}
+
+struct cgroup_subsys bcache_subsys = {
+        .create         = bcachecg_create,
+        .destroy        = bcachecg_destroy,
+        .subsys_id      = bcache_subsys_id,
+        .name           = "bcache",
+        .module         = THIS_MODULE,
+};
+EXPORT_SYMBOL_GPL(bcache_subsys);
+#endif
+
+static unsigned cache_mode(struct cached_dev *dc, struct bio *bio)
+{
+#ifdef CONFIG_CGROUP_BCACHE
+        int r = bch_bio_to_cgroup(bio)->cache_mode;
+        if (r >= 0)
+                return r;
+#endif
+        return BDEV_CACHE_MODE(&dc->sb);
+}
+
+static bool verify(struct cached_dev *dc, struct bio *bio)
+{
+#ifdef CONFIG_CGROUP_BCACHE
+        if (bch_bio_to_cgroup(bio)->verify)
+                return true;
+#endif
+        return dc->verify;
+}
+
+static void bio_csum(struct bio *bio, struct bkey *k)
+{
+        struct bio_vec *bv;
+        uint64_t csum = 0;
+        int i;
+
+        bio_for_each_segment(bv, bio, i) {
+                void *d = kmap(bv->bv_page) + bv->bv_offset;
+                csum = crc64_update(csum, d, bv->bv_len);
+                kunmap(bv->bv_page);
+        }
+
+        k->ptr[KEY_PTRS(k)] = csum & (~0ULL >> 1);
+}
+
+/* Insert data into cache */
+
+static void bio_invalidate(struct closure *cl)
+{
+        struct btree_op *op = container_of(cl, struct btree_op, cl);
+        struct bio *bio = op->cache_bio;
+
+        pr_debug("invalidating %i sectors from %llu",
+                 bio_sectors(bio), (uint64_t) bio->bi_sector);
+
+        while (bio_sectors(bio)) {
+                unsigned len = min(bio_sectors(bio), 1U << 14);
+
+                if (bch_keylist_realloc(&op->keys, 0, op->c))
+                        goto out;
+
+                bio->bi_sector  += len;
+                bio->bi_size    -= len << 9;
+
+                bch_keylist_add(&op->keys,
+                                &KEY(op->inode, bio->bi_sector, len));
+        }
+
+        op->insert_data_done = true;
+        bio_put(bio);
+out:
+        continue_at(cl, bch_journal, bcache_wq);
+}
+
+struct open_bucket {
+        struct list_head        list;
+        struct task_struct      *last;
+        unsigned                sectors_free;
+        BKEY_PADDED(key);
+};
+
+void bch_open_buckets_free(struct cache_set *c)
+{
+        struct open_bucket *b;
+
+        while (!list_empty(&c->data_buckets)) {
+                b = list_first_entry(&c->data_buckets,
+                                     struct open_bucket, list);
+                list_del(&b->list);
+                kfree(b);
+        }
+}
+
+int bch_open_buckets_alloc(struct cache_set *c)
+{
+        int i;
+
+        spin_lock_init(&c->data_bucket_lock);
+
+        for (i = 0; i < 6; i++) {
+                struct open_bucket *b = kzalloc(sizeof(*b), GFP_KERNEL);
+                if (!b)
+                        return -ENOMEM;
+
+                list_add(&b->list, &c->data_buckets);
+        }
+
+        return 0;
+}
+
+/*
+ * We keep multiple buckets open for writes, and try to segregate different
+ * write streams for better cache utilization: first we look for a bucket where
+ * the last write to it was sequential with the current write, and failing that
+ * we look for a bucket that was last used by the same task.
+ *
+ * The ideas is if you've got multiple tasks pulling data into the cache at the
+ * same time, you'll get better cache utilization if you try to segregate their
+ * data and preserve locality.
+ *
+ * For example, say you've starting Firefox at the same time you're copying a
+ * bunch of files. Firefox will likely end up being fairly hot and stay in the
+ * cache awhile, but the data you copied might not be; if you wrote all that
+ * data to the same buckets it'd get invalidated at the same time.
+ *
+ * Both of those tasks will be doing fairly random IO so we can't rely on
+ * detecting sequential IO to segregate their data, but going off of the task
+ * should be a sane heuristic.
+ */
+static struct open_bucket *pick_data_bucket(struct cache_set *c,
+                                            const struct bkey *search,
+                                            struct task_struct *task,
+                                            struct bkey *alloc)
+{
+        struct open_bucket *ret, *ret_task = NULL;
+
+        list_for_each_entry_reverse(ret, &c->data_buckets, list)
+                if (!bkey_cmp(&ret->key, search))
+                        goto found;
+                else if (ret->last == task)
+                        ret_task = ret;
+
+        ret = ret_task ?: list_first_entry(&c->data_buckets,
+                                           struct open_bucket, list);
+found:
+        if (!ret->sectors_free && KEY_PTRS(alloc)) {
+                ret->sectors_free = c->sb.bucket_size;
+                bkey_copy(&ret->key, alloc);
+                bkey_init(alloc);
+        }
+
+        if (!ret->sectors_free)
+                ret = NULL;
+
+        return ret;
+}
+
+/*
+ * Allocates some space in the cache to write to, and k to point to the newly
+ * allocated space, and updates KEY_SIZE(k) and KEY_OFFSET(k) (to point to the
+ * end of the newly allocated space).
+ *
+ * May allocate fewer sectors than @sectors, KEY_SIZE(k) indicates how many
+ * sectors were actually allocated.
+ *
+ * If s->writeback is true, will not fail.
+ */
+static bool bch_alloc_sectors(struct bkey *k, unsigned sectors,
+                              struct search *s)
+{
+        struct cache_set *c = s->op.c;
+        struct open_bucket *b;
+        BKEY_PADDED(key) alloc;
+        struct closure cl, *w = NULL;
+        unsigned i;
+
+        if (s->writeback) {
+                closure_init_stack(&cl);
+                w = &cl;
+        }
+
+        /*
+         * We might have to allocate a new bucket, which we can't do with a
+         * spinlock held. So if we have to allocate, we drop the lock, allocate
+         * and then retry. KEY_PTRS() indicates whether alloc points to
+         * allocated bucket(s).
+         */
+
+        bkey_init(&alloc.key);
+        spin_lock(&c->data_bucket_lock);
+
+        while (!(b = pick_data_bucket(c, k, s->task, &alloc.key))) {
+                unsigned watermark = s->op.write_prio
+                        ? WATERMARK_MOVINGGC
+                        : WATERMARK_NONE;
+
+                spin_unlock(&c->data_bucket_lock);
+
+                if (bch_bucket_alloc_set(c, watermark, &alloc.key, 1, w))
+                        return false;
+
+                spin_lock(&c->data_bucket_lock);
+        }
+
+        /*
+         * If we had to allocate, we might race and not need to allocate the
+         * second time we call find_data_bucket(). If we allocated a bucket but
+         * didn't use it, drop the refcount bch_bucket_alloc_set() took:
+         */
+        if (KEY_PTRS(&alloc.key))
+                __bkey_put(c, &alloc.key);
+
+        for (i = 0; i < KEY_PTRS(&b->key); i++)
+                EBUG_ON(ptr_stale(c, &b->key, i));
+
+        /* Set up the pointer to the space we're allocating: */
+
+        for (i = 0; i < KEY_PTRS(&b->key); i++)
+                k->ptr[i] = b->key.ptr[i];
+
+        sectors = min(sectors, b->sectors_free);
+
+        SET_KEY_OFFSET(k, KEY_OFFSET(k) + sectors);
+        SET_KEY_SIZE(k, sectors);
+        SET_KEY_PTRS(k, KEY_PTRS(&b->key));
+
+        /*
+         * Move b to the end of the lru, and keep track of what this bucket was
+         * last used for:
+         */
+        list_move_tail(&b->list, &c->data_buckets);
+        bkey_copy_key(&b->key, k);
+        b->last = s->task;
+
+        b->sectors_free -= sectors;
+
+        for (i = 0; i < KEY_PTRS(&b->key); i++) {
+                SET_PTR_OFFSET(&b->key, i, PTR_OFFSET(&b->key, i) + sectors);
+
+                atomic_long_add(sectors,
+                                &PTR_CACHE(c, &b->key, i)->sectors_written);
+        }
+
+        if (b->sectors_free < c->sb.block_size)
+                b->sectors_free = 0;
+
+        /*
+         * k takes refcounts on the buckets it points to until it's inserted
+         * into the btree, but if we're done with this bucket we just transfer
+         * get_data_bucket()'s refcount.
+         */
+        if (b->sectors_free)
+                for (i = 0; i < KEY_PTRS(&b->key); i++)
+                        atomic_inc(&PTR_BUCKET(c, &b->key, i)->pin);
+
+        spin_unlock(&c->data_bucket_lock);
+        return true;
+}
+
+static void bch_insert_data_error(struct closure *cl)
+{
+        struct btree_op *op = container_of(cl, struct btree_op, cl);
+
+        /*
+         * Our data write just errored, which means we've got a bunch of keys to
+         * insert that point to data that wasn't succesfully written.
+         *
+         * We don't have to insert those keys but we still have to invalidate
+         * that region of the cache - so, if we just strip off all the pointers
+         * from the keys we'll accomplish just that.
+         */
+
+        struct bkey *src = op->keys.bottom, *dst = op->keys.bottom;
+
+        while (src != op->keys.top) {
+                struct bkey *n = bkey_next(src);
+
+                SET_KEY_PTRS(src, 0);
+                bkey_copy(dst, src);
+
+                dst = bkey_next(dst);
+                src = n;
+        }
+
+        op->keys.top = dst;
+
+        bch_journal(cl);
+}
+
+static void bch_insert_data_endio(struct bio *bio, int error)
+{
+        struct closure *cl = bio->bi_private;
+        struct btree_op *op = container_of(cl, struct btree_op, cl);
+        struct search *s = container_of(op, struct search, op);
+
+        if (error) {
+                /* TODO: We could try to recover from this. */
+                if (s->writeback)
+                        s->error = error;
+                else if (s->write)
+                        set_closure_fn(cl, bch_insert_data_error, bcache_wq);
+                else
+                        set_closure_fn(cl, NULL, NULL);
+        }
+
+        bch_bbio_endio(op->c, bio, error, "writing data to cache");
+}
+
+static void bch_insert_data_loop(struct closure *cl)
+{
+        struct btree_op *op = container_of(cl, struct btree_op, cl);
+        struct search *s = container_of(op, struct search, op);
+        struct bio *bio = op->cache_bio, *n;
+
+        if (op->skip)
+                return bio_invalidate(cl);
+
+        if (atomic_sub_return(bio_sectors(bio), &op->c->sectors_to_gc) < 0) {
+                set_gc_sectors(op->c);
+                bch_queue_gc(op->c);
+        }
+
+        do {
+                unsigned i;
+                struct bkey *k;
+                struct bio_set *split = s->d
+                        ? s->d->bio_split : op->c->bio_split;
+
+                /* 1 for the device pointer and 1 for the chksum */
+                if (bch_keylist_realloc(&op->keys,
+                                        1 + (op->csum ? 1 : 0),
+                                        op->c))
+                        continue_at(cl, bch_journal, bcache_wq);
+
+                k = op->keys.top;
+                bkey_init(k);
+                SET_KEY_INODE(k, op->inode);
+                SET_KEY_OFFSET(k, bio->bi_sector);
+
+                if (!bch_alloc_sectors(k, bio_sectors(bio), s))
+                        goto err;
+
+                n = bch_bio_split(bio, KEY_SIZE(k), GFP_NOIO, split);
+                if (!n) {
+                        __bkey_put(op->c, k);
+                        continue_at(cl, bch_insert_data_loop, bcache_wq);
+                }
+
+                n->bi_end_io    = bch_insert_data_endio;
+                n->bi_private   = cl;
+
+                if (s->writeback) {
+                        SET_KEY_DIRTY(k, true);
+
+                        for (i = 0; i < KEY_PTRS(k); i++)
+                                SET_GC_MARK(PTR_BUCKET(op->c, k, i),
+                                            GC_MARK_DIRTY);
+                }
+
+                SET_KEY_CSUM(k, op->csum);
+                if (KEY_CSUM(k))
+                        bio_csum(n, k);
+
+                pr_debug("%s", pkey(k));
+                bch_keylist_push(&op->keys);
+
+                trace_bcache_cache_insert(n, n->bi_sector, n->bi_bdev);
+                n->bi_rw |= REQ_WRITE;
+                bch_submit_bbio(n, op->c, k, 0);
+        } while (n != bio);
+
+        op->insert_data_done = true;
+        continue_at(cl, bch_journal, bcache_wq);
+err:
+        /* bch_alloc_sectors() blocks if s->writeback = true */
+        BUG_ON(s->writeback);
+
+        /*
+         * But if it's not a writeback write we'd rather just bail out if
+         * there aren't any buckets ready to write to - it might take awhile and
+         * we might be starving btree writes for gc or something.
+         */
+
+        if (s->write) {
+                /*
+                 * Writethrough write: We can't complete the write until we've
+                 * updated the index. But we don't want to delay the write while
+                 * we wait for buckets to be freed up, so just invalidate the
+                 * rest of the write.
+                 */
+                op->skip = true;
+                return bio_invalidate(cl);
+        } else {
+                /*
+                 * From a cache miss, we can just insert the keys for the data
+                 * we have written or bail out if we didn't do anything.
+                 */
+                op->insert_data_done = true;
+                bio_put(bio);
+
+                if (!bch_keylist_empty(&op->keys))
+                        continue_at(cl, bch_journal, bcache_wq);
+                else
+                        closure_return(cl);
+        }
+}
+
+/**
+ * bch_insert_data - stick some data in the cache
+ *
+ * This is the starting point for any data to end up in a cache device; it could
+ * be from a normal write, or a writeback write, or a write to a flash only
+ * volume - it's also used by the moving garbage collector to compact data in
+ * mostly empty buckets.
+ *
+ * It first writes the data to the cache, creating a list of keys to be inserted
+ * (if the data had to be fragmented there will be multiple keys); after the
+ * data is written it calls bch_journal, and after the keys have been added to
+ * the next journal write they're inserted into the btree.
+ *
+ * It inserts the data in op->cache_bio; bi_sector is used for the key offset,
+ * and op->inode is used for the key inode.
+ *
+ * If op->skip is true, instead of inserting the data it invalidates the region
+ * of the cache represented by op->cache_bio and op->inode.
+ */
+void bch_insert_data(struct closure *cl)
+{
+        struct btree_op *op = container_of(cl, struct btree_op, cl);
+
+        bch_keylist_init(&op->keys);
+        bio_get(op->cache_bio);
+        bch_insert_data_loop(cl);
+}
+
+void bch_btree_insert_async(struct closure *cl)
+{
+        struct btree_op *op = container_of(cl, struct btree_op, cl);
+        struct search *s = container_of(op, struct search, op);
+
+        if (bch_btree_insert(op, op->c)) {
+                s->error                = -ENOMEM;
+                op->insert_data_done    = true;
+        }
+
+        if (op->insert_data_done) {
+                bch_keylist_free(&op->keys);
+                closure_return(cl);
+        } else
+                continue_at(cl, bch_insert_data_loop, bcache_wq);
+}
+
+/* Common code for the make_request functions */
+
+static void request_endio(struct bio *bio, int error)
+{
+        struct closure *cl = bio->bi_private;
+
+        if (error) {
+                struct search *s = container_of(cl, struct search, cl);
+                s->error = error;
+                /* Only cache read errors are recoverable */
+                s->recoverable = false;
+        }
+
+        bio_put(bio);
+        closure_put(cl);
+}
+
+void bch_cache_read_endio(struct bio *bio, int error)
+{
+        struct bbio *b = container_of(bio, struct bbio, bio);
+        struct closure *cl = bio->bi_private;
+        struct search *s = container_of(cl, struct search, cl);
+
+        /*
+         * If the bucket was reused while our bio was in flight, we might have
+         * read the wrong data. Set s->error but not error so it doesn't get
+         * counted against the cache device, but we'll still reread the data
+         * from the backing device.
+         */
+
+        if (error)
+                s->error = error;
+        else if (ptr_stale(s->op.c, &b->key, 0)) {
+                atomic_long_inc(&s->op.c->cache_read_races);
+                s->error = -EINTR;
+        }
+
+        bch_bbio_endio(s->op.c, bio, error, "reading from cache");
+}
+
+static void bio_complete(struct search *s)
+{
+        if (s->orig_bio) {
+                int cpu, rw = bio_data_dir(s->orig_bio);
+                unsigned long duration = jiffies - s->start_time;
+
+                cpu = part_stat_lock();
+                part_round_stats(cpu, &s->d->disk->part0);
+                part_stat_add(cpu, &s->d->disk->part0, ticks[rw], duration);
+                part_stat_unlock();
+
+                trace_bcache_request_end(s, s->orig_bio);
+                bio_endio(s->orig_bio, s->error);
+                s->orig_bio = NULL;
+        }
+}
+
+static void do_bio_hook(struct search *s)
+{
+        struct bio *bio = &s->bio.bio;
+        memcpy(bio, s->orig_bio, sizeof(struct bio));
+
+        bio->bi_end_io          = request_endio;
+        bio->bi_private         = &s->cl;
+        atomic_set(&bio->bi_cnt, 3);
+}
+
+static void search_free(struct closure *cl)
+{
+        struct search *s = container_of(cl, struct search, cl);
+        bio_complete(s);
+
+        if (s->op.cache_bio)
+                bio_put(s->op.cache_bio);
+
+        if (s->unaligned_bvec)
+                mempool_free(s->bio.bio.bi_io_vec, s->d->unaligned_bvec);
+
+        closure_debug_destroy(cl);
+        mempool_free(s, s->d->c->search);
+}
+
+static struct search *search_alloc(struct bio *bio, struct bcache_device *d)
+{
+        struct bio_vec *bv;
+        struct search *s = mempool_alloc(d->c->search, GFP_NOIO);
+        memset(s, 0, offsetof(struct search, op.keys));
+
+        __closure_init(&s->cl, NULL);
+
+        s->op.inode             = d->id;
+        s->op.c                 = d->c;
+        s->d                    = d;
+        s->op.lock              = -1;
+        s->task                 = current;
+        s->orig_bio             = bio;
+        s->write                = (bio->bi_rw & REQ_WRITE) != 0;
+        s->op.flush_journal     = (bio->bi_rw & REQ_FLUSH) != 0;
+        s->op.skip              = (bio->bi_rw & REQ_DISCARD) != 0;
+        s->recoverable          = 1;
+        s->start_time           = jiffies;
+        do_bio_hook(s);
+
+        if (bio->bi_size != bio_segments(bio) * PAGE_SIZE) {
+                bv = mempool_alloc(d->unaligned_bvec, GFP_NOIO);
+                memcpy(bv, bio_iovec(bio),
+                       sizeof(struct bio_vec) * bio_segments(bio));
+
+                s->bio.bio.bi_io_vec    = bv;
+                s->unaligned_bvec       = 1;
+        }
+
+        return s;
+}
+
+static void btree_read_async(struct closure *cl)
+{
+        struct btree_op *op = container_of(cl, struct btree_op, cl);
+
+        int ret = btree_root(search_recurse, op->c, op);
+
+        if (ret == -EAGAIN)
+                continue_at(cl, btree_read_async, bcache_wq);
+
+        closure_return(cl);
+}
+
+/* Cached devices */
+
+static void cached_dev_bio_complete(struct closure *cl)
+{
+        struct search *s = container_of(cl, struct search, cl);
+        struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
+
+        search_free(cl);
+        cached_dev_put(dc);
+}
+
+/* Process reads */
+
+static void cached_dev_read_complete(struct closure *cl)
+{
+        struct search *s = container_of(cl, struct search, cl);
+
+        if (s->op.insert_collision)
+                bch_mark_cache_miss_collision(s);
+
+        if (s->op.cache_bio) {
+                int i;
+                struct bio_vec *bv;
+
+                __bio_for_each_segment(bv, s->op.cache_bio, i, 0)
+                        __free_page(bv->bv_page);
+        }
+
+        cached_dev_bio_complete(cl);
+}
+
+static void request_read_error(struct closure *cl)
+{
+        struct search *s = container_of(cl, struct search, cl);
+        struct bio_vec *bv;
+        int i;
+
+        if (s->recoverable) {
+                /* The cache read failed, but we can retry from the backing
+                 * device.
+                 */
+                pr_debug("recovering at sector %llu",
+                         (uint64_t) s->orig_bio->bi_sector);
+
+                s->error = 0;
+                bv = s->bio.bio.bi_io_vec;
+                do_bio_hook(s);
+                s->bio.bio.bi_io_vec = bv;
+
+                if (!s->unaligned_bvec)
+                        bio_for_each_segment(bv, s->orig_bio, i)
+                                bv->bv_offset = 0, bv->bv_len = PAGE_SIZE;
+                else
+                        memcpy(s->bio.bio.bi_io_vec,
+                               bio_iovec(s->orig_bio),
+                               sizeof(struct bio_vec) *
+                               bio_segments(s->orig_bio));
+
+                /* XXX: invalidate cache */
+
+                trace_bcache_read_retry(&s->bio.bio);
+                closure_bio_submit(&s->bio.bio, &s->cl, s->d);
+        }
+
+        continue_at(cl, cached_dev_read_complete, NULL);
+}
+
+static void request_read_done(struct closure *cl)
+{
+        struct search *s = container_of(cl, struct search, cl);
+        struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
+
+        /*
+         * s->cache_bio != NULL implies that we had a cache miss; cache_bio now
+         * contains data ready to be inserted into the cache.
+         *
+         * First, we copy the data we just read from cache_bio's bounce buffers
+         * to the buffers the original bio pointed to:
+         */
+
+        if (s->op.cache_bio) {
+                struct bio_vec *src, *dst;
+                unsigned src_offset, dst_offset, bytes;
+                void *dst_ptr;
+
+                bio_reset(s->op.cache_bio);
+                s->op.cache_bio->bi_sector      = s->cache_miss->bi_sector;
+                s->op.cache_bio->bi_bdev        = s->cache_miss->bi_bdev;
+                s->op.cache_bio->bi_size        = s->cache_bio_sectors << 9;
+                bio_map(s->op.cache_bio, NULL);
+
+                src = bio_iovec(s->op.cache_bio);
+                dst = bio_iovec(s->cache_miss);
+                src_offset = src->bv_offset;
+                dst_offset = dst->bv_offset;
+                dst_ptr = kmap(dst->bv_page);
+
+                while (1) {
+                        if (dst_offset == dst->bv_offset + dst->bv_len) {
+                                kunmap(dst->bv_page);
+                                dst++;
+                                if (dst == bio_iovec_idx(s->cache_miss,
+                                                s->cache_miss->bi_vcnt))
+                                        break;
+
+                                dst_offset = dst->bv_offset;
+                                dst_ptr = kmap(dst->bv_page);
+                        }
+
+                        if (src_offset == src->bv_offset + src->bv_len) {
+                                src++;
+                                if (src == bio_iovec_idx(s->op.cache_bio,
+                                                 s->op.cache_bio->bi_vcnt))
+                                        BUG();
+
+                                src_offset = src->bv_offset;
+                        }
+
+                        bytes = min(dst->bv_offset + dst->bv_len - dst_offset,
+                                    src->bv_offset + src->bv_len - src_offset);
+
+                        memcpy(dst_ptr + dst_offset,
+                               page_address(src->bv_page) + src_offset,
+                               bytes);
+
+                        src_offset      += bytes;
+                        dst_offset      += bytes;
+                }
+
+                bio_put(s->cache_miss);
+                s->cache_miss = NULL;
+        }
+
+        if (verify(dc, &s->bio.bio) && s->recoverable)
+                bch_data_verify(s);
+
+        bio_complete(s);
+
+        if (s->op.cache_bio &&
+            !test_bit(CACHE_SET_STOPPING, &s->op.c->flags)) {
+                s->op.type = BTREE_REPLACE;
+                closure_call(&s->op.cl, bch_insert_data, NULL, cl);
+        }
+
+        continue_at(cl, cached_dev_read_complete, NULL);
+}
+
+static void request_read_done_bh(struct closure *cl)
+{
+        struct search *s = container_of(cl, struct search, cl);
+        struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
+
+        bch_mark_cache_accounting(s, !s->cache_miss, s->op.skip);
+
+        if (s->error)
+                continue_at_nobarrier(cl, request_read_error, bcache_wq);
+        else if (s->op.cache_bio || verify(dc, &s->bio.bio))
+                continue_at_nobarrier(cl, request_read_done, bcache_wq);
+        else
+                continue_at_nobarrier(cl, cached_dev_read_complete, NULL);
+}
+
+static int cached_dev_cache_miss(struct btree *b, struct search *s,
+                                 struct bio *bio, unsigned sectors)
+{
+        int ret = 0;
+        unsigned reada;
+        struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
+        struct bio *miss;
+
+        miss = bch_bio_split(bio, sectors, GFP_NOIO, s->d->bio_split);
+        if (!miss)
+                return -EAGAIN;
+
+        if (miss == bio)
+                s->op.lookup_done = true;
+
+        miss->bi_end_io         = request_endio;
+        miss->bi_private        = &s->cl;
+
+        if (s->cache_miss || s->op.skip)
+                goto out_submit;
+
+        if (miss != bio ||
+            (bio->bi_rw & REQ_RAHEAD) ||
+            (bio->bi_rw & REQ_META) ||
+            s->op.c->gc_stats.in_use >= CUTOFF_CACHE_READA)
+                reada = 0;
+        else {
+                reada = min(dc->readahead >> 9,
+                            sectors - bio_sectors(miss));
+
+                if (bio_end(miss) + reada > bdev_sectors(miss->bi_bdev))
+                        reada = bdev_sectors(miss->bi_bdev) - bio_end(miss);
+        }
+
+        s->cache_bio_sectors = bio_sectors(miss) + reada;
+        s->op.cache_bio = bio_alloc_bioset(GFP_NOWAIT,
+                        DIV_ROUND_UP(s->cache_bio_sectors, PAGE_SECTORS),
+                        dc->disk.bio_split);
+
+        if (!s->op.cache_bio)
+                goto out_submit;
+
+        s->op.cache_bio->bi_sector      = miss->bi_sector;
+        s->op.cache_bio->bi_bdev        = miss->bi_bdev;
+        s->op.cache_bio->bi_size        = s->cache_bio_sectors << 9;
+
+        s->op.cache_bio->bi_end_io      = request_endio;
+        s->op.cache_bio->bi_private     = &s->cl;
+
+        /* btree_search_recurse()'s btree iterator is no good anymore */
+        ret = -EINTR;
+        if (!bch_btree_insert_check_key(b, &s->op, s->op.cache_bio))
+                goto out_put;
+
+        bio_map(s->op.cache_bio, NULL);
+        if (bio_alloc_pages(s->op.cache_bio, __GFP_NOWARN|GFP_NOIO))
+                goto out_put;
+
+        s->cache_miss = miss;
+        bio_get(s->op.cache_bio);
+
+        trace_bcache_cache_miss(s->orig_bio);
+        closure_bio_submit(s->op.cache_bio, &s->cl, s->d);
+
+        return ret;
+out_put:
+        bio_put(s->op.cache_bio);
+        s->op.cache_bio = NULL;
+out_submit:
+        closure_bio_submit(miss, &s->cl, s->d);
+        return ret;
+}
+
+static void request_read(struct cached_dev *dc, struct search *s)
+{
+        struct closure *cl = &s->cl;
+
+        check_should_skip(dc, s);
+        closure_call(&s->op.cl, btree_read_async, NULL, cl);
+
+        continue_at(cl, request_read_done_bh, NULL);
+}
+
+/* Process writes */
+
+static void cached_dev_write_complete(struct closure *cl)
+{
+        struct search *s = container_of(cl, struct search, cl);
+        struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
+
+        up_read_non_owner(&dc->writeback_lock);
+        cached_dev_bio_complete(cl);
+}
+
+static bool should_writeback(struct cached_dev *dc, struct bio *bio)
+{
+        unsigned threshold = (bio->bi_rw & REQ_SYNC)
+                ? CUTOFF_WRITEBACK_SYNC
+                : CUTOFF_WRITEBACK;
+
+        return !atomic_read(&dc->disk.detaching) &&
+                cache_mode(dc, bio) == CACHE_MODE_WRITEBACK &&
+                dc->disk.c->gc_stats.in_use < threshold;
+}
+
+static void request_write(struct cached_dev *dc, struct search *s)
+{
+        struct closure *cl = &s->cl;
+        struct bio *bio = &s->bio.bio;
+        struct bkey start, end;
+        start = KEY(dc->disk.id, bio->bi_sector, 0);
+        end = KEY(dc->disk.id, bio_end(bio), 0);
+
+        bch_keybuf_check_overlapping(&s->op.c->moving_gc_keys, &start, &end);
+
+        check_should_skip(dc, s);
+        down_read_non_owner(&dc->writeback_lock);
+
+        if (bch_keybuf_check_overlapping(&dc->writeback_keys, &start, &end)) {
+                s->op.skip      = false;
+                s->writeback    = true;
+        }
+
+        if (bio->bi_rw & REQ_DISCARD)
+                goto skip;
+
+        if (s->op.skip)
+                goto skip;
+
+        if (should_writeback(dc, s->orig_bio))
+                s->writeback = true;
+
+        if (!s->writeback) {
+                s->op.cache_bio = bio_clone_bioset(bio, GFP_NOIO,
+                                                   dc->disk.bio_split);
+
+                trace_bcache_writethrough(s->orig_bio);
+                closure_bio_submit(bio, cl, s->d);
+        } else {
+                s->op.cache_bio = bio;
+                trace_bcache_writeback(s->orig_bio);
+                bch_writeback_add(dc, bio_sectors(bio));
+        }
+out:
+        closure_call(&s->op.cl, bch_insert_data, NULL, cl);
+        continue_at(cl, cached_dev_write_complete, NULL);
+skip:
+        s->op.skip = true;
+        s->op.cache_bio = s->orig_bio;
+        bio_get(s->op.cache_bio);
+        trace_bcache_write_skip(s->orig_bio);
+
+        if ((bio->bi_rw & REQ_DISCARD) &&
+            !blk_queue_discard(bdev_get_queue(dc->bdev)))
+                goto out;
+
+        closure_bio_submit(bio, cl, s->d);
+        goto out;
+}
+
+static void request_nodata(struct cached_dev *dc, struct search *s)
+{
+        struct closure *cl = &s->cl;
+        struct bio *bio = &s->bio.bio;
+
+        if (bio->bi_rw & REQ_DISCARD) {
+                request_write(dc, s);
+                return;
+        }
+
+        if (s->op.flush_journal)
+                bch_journal_meta(s->op.c, cl);
+
+        closure_bio_submit(bio, cl, s->d);
+
+        continue_at(cl, cached_dev_bio_complete, NULL);
+}
+
+/* Cached devices - read & write stuff */
+
+int bch_get_congested(struct cache_set *c)
+{
+        int i;
+
+        if (!c->congested_read_threshold_us &&
+            !c->congested_write_threshold_us)
+                return 0;
+
+        i = (local_clock_us() - c->congested_last_us) / 1024;
+        if (i < 0)
+                return 0;
+
+        i += atomic_read(&c->congested);
+        if (i >= 0)
+                return 0;
+
+        i += CONGESTED_MAX;
+
+        return i <= 0 ? 1 : fract_exp_two(i, 6);
+}
+
+static void add_sequential(struct task_struct *t)
+{
+        ewma_add(t->sequential_io_avg,
+                 t->sequential_io, 8, 0);
+
+        t->sequential_io = 0;
+}
+
+static void check_should_skip(struct cached_dev *dc, struct search *s)
+{
+        struct hlist_head *iohash(uint64_t k)
+        { return &dc->io_hash[hash_64(k, RECENT_IO_BITS)]; }
+
+        struct cache_set *c = s->op.c;
+        struct bio *bio = &s->bio.bio;
+
+        long rand;
+        int cutoff = bch_get_congested(c);
+        unsigned mode = cache_mode(dc, bio);
+
+        if (atomic_read(&dc->disk.detaching) ||
+            c->gc_stats.in_use > CUTOFF_CACHE_ADD ||
+            (bio->bi_rw & REQ_DISCARD))
+                goto skip;
+
+        if (mode == CACHE_MODE_NONE ||
+            (mode == CACHE_MODE_WRITEAROUND &&
+             (bio->bi_rw & REQ_WRITE)))
+                goto skip;
+
+        if (bio->bi_sector   & (c->sb.block_size - 1) ||
+            bio_sectors(bio) & (c->sb.block_size - 1)) {
+                pr_debug("skipping unaligned io");
+                goto skip;
+        }
+
+        if (!cutoff) {
+                cutoff = dc->sequential_cutoff >> 9;
+
+                if (!cutoff)
+                        goto rescale;
+
+                if (mode == CACHE_MODE_WRITEBACK &&
+                    (bio->bi_rw & REQ_WRITE) &&
+                    (bio->bi_rw & REQ_SYNC))
+                        goto rescale;
+        }
+
+        if (dc->sequential_merge) {
+                struct io *i;
+
+                spin_lock(&dc->io_lock);
+
+                hlist_for_each_entry(i, iohash(bio->bi_sector), hash)
+                        if (i->last == bio->bi_sector &&
+                            time_before(jiffies, i->jiffies))
+                                goto found;
+
+                i = list_first_entry(&dc->io_lru, struct io, lru);
+
+                add_sequential(s->task);
+                i->sequential = 0;
+found:
+                if (i->sequential + bio->bi_size > i->sequential)
+                        i->sequential   += bio->bi_size;
+
+                i->last                  = bio_end(bio);
+                i->jiffies               = jiffies + msecs_to_jiffies(5000);
+                s->task->sequential_io   = i->sequential;
+
+                hlist_del(&i->hash);
+                hlist_add_head(&i->hash, iohash(i->last));
+                list_move_tail(&i->lru, &dc->io_lru);
+
+                spin_unlock(&dc->io_lock);
+        } else {
+                s->task->sequential_io = bio->bi_size;
+
+                add_sequential(s->task);
+        }
+
+        rand = get_random_int();
+        cutoff -= bitmap_weight(&rand, BITS_PER_LONG);
+
+        if (cutoff <= (int) (max(s->task->sequential_io,
+                                 s->task->sequential_io_avg) >> 9))
+                goto skip;
+
+rescale:
+        bch_rescale_priorities(c, bio_sectors(bio));
+        return;
+skip:
+        bch_mark_sectors_bypassed(s, bio_sectors(bio));
+        s->op.skip = true;
+}
+
+static void cached_dev_make_request(struct request_queue *q, struct bio *bio)
+{
+        struct search *s;
+        struct bcache_device *d = bio->bi_bdev->bd_disk->private_data;
+        struct cached_dev *dc = container_of(d, struct cached_dev, disk);
+        int cpu, rw = bio_data_dir(bio);
+
+        cpu = part_stat_lock();
+        part_stat_inc(cpu, &d->disk->part0, ios[rw]);
+        part_stat_add(cpu, &d->disk->part0, sectors[rw], bio_sectors(bio));
+        part_stat_unlock();
+
+        bio->bi_bdev = dc->bdev;
+        bio->bi_sector += BDEV_DATA_START;
+
+        if (cached_dev_get(dc)) {
+                s = search_alloc(bio, d);
+                trace_bcache_request_start(s, bio);
+
+                if (!bio_has_data(bio))
+                        request_nodata(dc, s);
+                else if (rw)
+                        request_write(dc, s);
+                else
+                        request_read(dc, s);
+        } else {
+                if ((bio->bi_rw & REQ_DISCARD) &&
+                    !blk_queue_discard(bdev_get_queue(dc->bdev)))
+                        bio_endio(bio, 0);
+                else
+                        bch_generic_make_request(bio, &d->bio_split_hook);
+        }
+}
+
+static int cached_dev_ioctl(struct bcache_device *d, fmode_t mode,
+                            unsigned int cmd, unsigned long arg)
+{
+        struct cached_dev *dc = container_of(d, struct cached_dev, disk);
+        return __blkdev_driver_ioctl(dc->bdev, mode, cmd, arg);
+}
+
+static int cached_dev_congested(void *data, int bits)
+{
+        struct bcache_device *d = data;
+        struct cached_dev *dc = container_of(d, struct cached_dev, disk);
+        struct request_queue *q = bdev_get_queue(dc->bdev);
+        int ret = 0;
+
+        if (bdi_congested(&q->backing_dev_info, bits))
+                return 1;
+
+        if (cached_dev_get(dc)) {
+                unsigned i;
+                struct cache *ca;
+
+                for_each_cache(ca, d->c, i) {
+                        q = bdev_get_queue(ca->bdev);
+                        ret |= bdi_congested(&q->backing_dev_info, bits);
+                }
+
+                cached_dev_put(dc);
+        }
+
+        return ret;
+}
+
+void bch_cached_dev_request_init(struct cached_dev *dc)
+{
+        struct gendisk *g = dc->disk.disk;
+
+        g->queue->make_request_fn               = cached_dev_make_request;
+        g->queue->backing_dev_info.congested_fn = cached_dev_congested;
+        dc->disk.cache_miss                     = cached_dev_cache_miss;
+        dc->disk.ioctl                          = cached_dev_ioctl;
+}
+
+/* Flash backed devices */
+
+static int flash_dev_cache_miss(struct btree *b, struct search *s,
+                                struct bio *bio, unsigned sectors)
+{
+        /* Zero fill bio */
+
+        while (bio->bi_idx != bio->bi_vcnt) {
+                struct bio_vec *bv = bio_iovec(bio);
+                unsigned j = min(bv->bv_len >> 9, sectors);
+
+                void *p = kmap(bv->bv_page);
+                memset(p + bv->bv_offset, 0, j << 9);
+                kunmap(bv->bv_page);
+
+                bv->bv_len      -= j << 9;
+                bv->bv_offset   += j << 9;
+
+                if (bv->bv_len)
+                        return 0;
+
+                bio->bi_sector  += j;
+                bio->bi_size    -= j << 9;
+
+                bio->bi_idx++;
+                sectors         -= j;
+        }
+
+        s->op.lookup_done = true;
+
+        return 0;
+}
+
+static void flash_dev_make_request(struct request_queue *q, struct bio *bio)
+{
+        struct search *s;
+        struct closure *cl;
+        struct bcache_device *d = bio->bi_bdev->bd_disk->private_data;
+        int cpu, rw = bio_data_dir(bio);
+
+        cpu = part_stat_lock();
+        part_stat_inc(cpu, &d->disk->part0, ios[rw]);
+        part_stat_add(cpu, &d->disk->part0, sectors[rw], bio_sectors(bio));
+        part_stat_unlock();
+
+        s = search_alloc(bio, d);
+        cl = &s->cl;
+        bio = &s->bio.bio;
+
+        trace_bcache_request_start(s, bio);
+
+        if (bio_has_data(bio) && !rw) {
+                closure_call(&s->op.cl, btree_read_async, NULL, cl);
+        } else if (bio_has_data(bio) || s->op.skip) {
+                bch_keybuf_check_overlapping(&s->op.c->moving_gc_keys,
+                                             &KEY(d->id, bio->bi_sector, 0),
+                                             &KEY(d->id, bio_end(bio), 0));
+
+                s->writeback    = true;
+                s->op.cache_bio = bio;
+
+                closure_call(&s->op.cl, bch_insert_data, NULL, cl);
+        } else {
+                /* No data - probably a cache flush */
+                if (s->op.flush_journal)
+                        bch_journal_meta(s->op.c, cl);
+        }
+
+        continue_at(cl, search_free, NULL);
+}
+
+static int flash_dev_ioctl(struct bcache_device *d, fmode_t mode,
+                           unsigned int cmd, unsigned long arg)
+{
+        return -ENOTTY;
+}
+
+static int flash_dev_congested(void *data, int bits)
+{
+        struct bcache_device *d = data;
+        struct request_queue *q;
+        struct cache *ca;
+        unsigned i;
+        int ret = 0;
+
+        for_each_cache(ca, d->c, i) {
+                q = bdev_get_queue(ca->bdev);
+                ret |= bdi_congested(&q->backing_dev_info, bits);
+        }
+
+        return ret;
+}
+
+void bch_flash_dev_request_init(struct bcache_device *d)
+{
+        struct gendisk *g = d->disk;
+
+        g->queue->make_request_fn               = flash_dev_make_request;
+        g->queue->backing_dev_info.congested_fn = flash_dev_congested;
+        d->cache_miss                           = flash_dev_cache_miss;
+        d->ioctl                                = flash_dev_ioctl;
+}
+
+void bch_request_exit(void)
+{
+#ifdef CONFIG_CGROUP_BCACHE
+        cgroup_unload_subsys(&bcache_subsys);
+#endif
+        if (bch_search_cache)
+                kmem_cache_destroy(bch_search_cache);
+}
+
+int __init bch_request_init(void)
+{
+        bch_search_cache = KMEM_CACHE(search, 0);
+        if (!bch_search_cache)
+                return -ENOMEM;
+
+#ifdef CONFIG_CGROUP_BCACHE
+        cgroup_load_subsys(&bcache_subsys);
+        init_bch_cgroup(&bcache_default_cgroup);
+
+        cgroup_add_cftypes(&bcache_subsys, bch_files);
+#endif
+        return 0;
+}
diff --git a/drivers/md/bcache/request.h b/drivers/md/bcache/request.h
new file mode 100644
index 000000000000..254d9ab5707c
--- /dev/null
+++ b/drivers/md/bcache/request.h
@@ -0,0 +1,62 @@
+#ifndef _BCACHE_REQUEST_H_
+#define _BCACHE_REQUEST_H_
+
+#include <linux/cgroup.h>
+
+struct search {
+        /* Stack frame for bio_complete */
+        struct closure          cl;
+
+        struct bcache_device    *d;
+        struct task_struct      *task;
+
+        struct bbio             bio;
+        struct bio              *orig_bio;
+        struct bio              *cache_miss;
+        unsigned                cache_bio_sectors;
+
+        unsigned                recoverable:1;
+        unsigned                unaligned_bvec:1;
+
+        unsigned                write:1;
+        unsigned                writeback:1;
+
+        /* IO error returned to s->bio */
+        short                   error;
+        unsigned long           start_time;
+
+        /* Anything past op->keys won't get zeroed in do_bio_hook */
+        struct btree_op         op;
+};
+
+void bch_cache_read_endio(struct bio *, int);
+int bch_get_congested(struct cache_set *);
+void bch_insert_data(struct closure *cl);
+void bch_btree_insert_async(struct closure *);
+void bch_cache_read_endio(struct bio *, int);
+
+void bch_open_buckets_free(struct cache_set *);
+int bch_open_buckets_alloc(struct cache_set *);
+
+void bch_cached_dev_request_init(struct cached_dev *dc);
+void bch_flash_dev_request_init(struct bcache_device *d);
+
+extern struct kmem_cache *bch_search_cache, *bch_passthrough_cache;
+
+struct bch_cgroup {
+#ifdef CONFIG_CGROUP_BCACHE
+        struct cgroup_subsys_state      css;
+#endif
+        /*
+         * We subtract one from the index into bch_cache_modes[], so that
+         * default == -1; this makes it so the rest match up with d->cache_mode,
+         * and we use d->cache_mode if cgrp->cache_mode < 0
+         */
+        short                           cache_mode;
+        bool                            verify;
+        struct cache_stat_collector     stats;
+};
+
+struct bch_cgroup *bch_bio_to_cgroup(struct bio *bio);
+
+#endif /* _BCACHE_REQUEST_H_ */
diff --git a/drivers/md/bcache/stats.c b/drivers/md/bcache/stats.c
new file mode 100644
index 000000000000..bf6cf9518c89
--- /dev/null
+++ b/drivers/md/bcache/stats.c
@@ -0,0 +1,245 @@
+/*
+ * bcache stats code
+ *
+ * Copyright 2012 Google, Inc.
+ */
+
+#include "bcache.h"
+#include "stats.h"
+#include "btree.h"
+#include "request.h"
+#include "sysfs.h"
+
+/*
+ * We keep absolute totals of various statistics, and addionally a set of three
+ * rolling averages.
+ *
+ * Every so often, a timer goes off and rescales the rolling averages.
+ * accounting_rescale[] is how many times the timer has to go off before we
+ * rescale each set of numbers; that gets us half lives of 5 minutes, one hour,
+ * and one day.
+ *
+ * accounting_delay is how often the timer goes off - 22 times in 5 minutes,
+ * and accounting_weight is what we use to rescale:
+ *
+ * pow(31 / 32, 22) ~= 1/2
+ *
+ * So that we don't have to increment each set of numbers every time we (say)
+ * get a cache hit, we increment a single atomic_t in acc->collector, and when
+ * the rescale function runs it resets the atomic counter to 0 and adds its
+ * old value to each of the exported numbers.
+ *
+ * To reduce rounding error, the numbers in struct cache_stats are all
+ * stored left shifted by 16, and scaled back in the sysfs show() function.
+ */
+
+static const unsigned DAY_RESCALE               = 288;
+static const unsigned HOUR_RESCALE              = 12;
+static const unsigned FIVE_MINUTE_RESCALE       = 1;
+static const unsigned accounting_delay          = (HZ * 300) / 22;
+static const unsigned accounting_weight         = 32;
+
+/* sysfs reading/writing */
+
+read_attribute(cache_hits);
+read_attribute(cache_misses);
+read_attribute(cache_bypass_hits);
+read_attribute(cache_bypass_misses);
+read_attribute(cache_hit_ratio);
+read_attribute(cache_readaheads);
+read_attribute(cache_miss_collisions);
+read_attribute(bypassed);
+
+SHOW(bch_stats)
+{
+        struct cache_stats *s =
+                container_of(kobj, struct cache_stats, kobj);
+#define var(stat)               (s->stat >> 16)
+        var_print(cache_hits);
+        var_print(cache_misses);
+        var_print(cache_bypass_hits);
+        var_print(cache_bypass_misses);
+
+        sysfs_print(cache_hit_ratio,
+                    DIV_SAFE(var(cache_hits) * 100,
+                             var(cache_hits) + var(cache_misses)));
+
+        var_print(cache_readaheads);
+        var_print(cache_miss_collisions);
+        sysfs_hprint(bypassed,  var(sectors_bypassed) << 9);
+#undef var
+        return 0;
+}
+
+STORE(bch_stats)
+{
+        return size;
+}
+
+static void bch_stats_release(struct kobject *k)
+{
+}
+
+static struct attribute *bch_stats_files[] = {
+        &sysfs_cache_hits,
+        &sysfs_cache_misses,
+        &sysfs_cache_bypass_hits,
+        &sysfs_cache_bypass_misses,
+        &sysfs_cache_hit_ratio,
+        &sysfs_cache_readaheads,
+        &sysfs_cache_miss_collisions,
+        &sysfs_bypassed,
+        NULL
+};
+static KTYPE(bch_stats);
+
+static void scale_accounting(unsigned long data);
+
+void bch_cache_accounting_init(struct cache_accounting *acc, struct closure *parent)
+{
+        kobject_init(&acc->total.kobj,          &bch_stats_ktype);
+        kobject_init(&acc->five_minute.kobj,    &bch_stats_ktype);
+        kobject_init(&acc->hour.kobj,           &bch_stats_ktype);
+        kobject_init(&acc->day.kobj,            &bch_stats_ktype);
+
+        closure_init(&acc->cl, parent);
+        init_timer(&acc->timer);
+        acc->timer.expires      = jiffies + accounting_delay;
+        acc->timer.data         = (unsigned long) acc;
+        acc->timer.function     = scale_accounting;
+        add_timer(&acc->timer);
+}
+
+int bch_cache_accounting_add_kobjs(struct cache_accounting *acc,
+                                   struct kobject *parent)
+{
+        int ret = kobject_add(&acc->total.kobj, parent,
+                              "stats_total");
+        ret = ret ?: kobject_add(&acc->five_minute.kobj, parent,
+                                 "stats_five_minute");
+        ret = ret ?: kobject_add(&acc->hour.kobj, parent,
+                                 "stats_hour");
+        ret = ret ?: kobject_add(&acc->day.kobj, parent,
+                                 "stats_day");
+        return ret;
+}
+
+void bch_cache_accounting_clear(struct cache_accounting *acc)
+{
+        memset(&acc->total.cache_hits,
+               0,
+               sizeof(unsigned long) * 7);
+}
+
+void bch_cache_accounting_destroy(struct cache_accounting *acc)
+{
+        kobject_put(&acc->total.kobj);
+        kobject_put(&acc->five_minute.kobj);
+        kobject_put(&acc->hour.kobj);
+        kobject_put(&acc->day.kobj);
+
+        atomic_set(&acc->closing, 1);
+        if (del_timer_sync(&acc->timer))
+                closure_return(&acc->cl);
+}
+
+/* EWMA scaling */
+
+static void scale_stat(unsigned long *stat)
+{
+        *stat =  ewma_add(*stat, 0, accounting_weight, 0);
+}
+
+static void scale_stats(struct cache_stats *stats, unsigned long rescale_at)
+{
+        if (++stats->rescale == rescale_at) {
+                stats->rescale = 0;
+                scale_stat(&stats->cache_hits);
+                scale_stat(&stats->cache_misses);
+                scale_stat(&stats->cache_bypass_hits);
+                scale_stat(&stats->cache_bypass_misses);
+                scale_stat(&stats->cache_readaheads);
+                scale_stat(&stats->cache_miss_collisions);
+                scale_stat(&stats->sectors_bypassed);
+        }
+}
+
+static void scale_accounting(unsigned long data)
+{
+        struct cache_accounting *acc = (struct cache_accounting *) data;
+
+#define move_stat(name) do {                                            \
+        unsigned t = atomic_xchg(&acc->collector.name, 0);              \
+        t <<= 16;                                                       \
+        acc->five_minute.name += t;                                     \
+        acc->hour.name += t;                                            \
+        acc->day.name += t;                                             \
+        acc->total.name += t;                                           \
+} while (0)
+
+        move_stat(cache_hits);
+        move_stat(cache_misses);
+        move_stat(cache_bypass_hits);
+        move_stat(cache_bypass_misses);
+        move_stat(cache_readaheads);
+        move_stat(cache_miss_collisions);
+        move_stat(sectors_bypassed);
+
+        scale_stats(&acc->total, 0);
+        scale_stats(&acc->day, DAY_RESCALE);
+        scale_stats(&acc->hour, HOUR_RESCALE);
+        scale_stats(&acc->five_minute, FIVE_MINUTE_RESCALE);
+
+        acc->timer.expires += accounting_delay;
+
+        if (!atomic_read(&acc->closing))
+                add_timer(&acc->timer);
+        else
+                closure_return(&acc->cl);
+}
+
+static void mark_cache_stats(struct cache_stat_collector *stats,
+                             bool hit, bool bypass)
+{
+        if (!bypass)
+                if (hit)
+                        atomic_inc(&stats->cache_hits);
+                else
+                        atomic_inc(&stats->cache_misses);
+        else
+                if (hit)
+                        atomic_inc(&stats->cache_bypass_hits);
+                else
+                        atomic_inc(&stats->cache_bypass_misses);
+}
+
+void bch_mark_cache_accounting(struct search *s, bool hit, bool bypass)
+{
+        struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
+        mark_cache_stats(&dc->accounting.collector, hit, bypass);
+        mark_cache_stats(&s->op.c->accounting.collector, hit, bypass);
+#ifdef CONFIG_CGROUP_BCACHE
+        mark_cache_stats(&(bch_bio_to_cgroup(s->orig_bio)->stats), hit, bypass);
+#endif
+}
+
+void bch_mark_cache_readahead(struct search *s)
+{
+        struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
+        atomic_inc(&dc->accounting.collector.cache_readaheads);
+        atomic_inc(&s->op.c->accounting.collector.cache_readaheads);
+}
+
+void bch_mark_cache_miss_collision(struct search *s)
+{
+        struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
+        atomic_inc(&dc->accounting.collector.cache_miss_collisions);
+        atomic_inc(&s->op.c->accounting.collector.cache_miss_collisions);
+}
+
+void bch_mark_sectors_bypassed(struct search *s, int sectors)
+{
+        struct cached_dev *dc = container_of(s->d, struct cached_dev, disk);
+        atomic_add(sectors, &dc->accounting.collector.sectors_bypassed);
+        atomic_add(sectors, &s->op.c->accounting.collector.sectors_bypassed);
+}
diff --git a/drivers/md/bcache/stats.h b/drivers/md/bcache/stats.h
new file mode 100644
index 000000000000..c7c7a8fd29fe
--- /dev/null
+++ b/drivers/md/bcache/stats.h
@@ -0,0 +1,58 @@
+#ifndef _BCACHE_STATS_H_
+#define _BCACHE_STATS_H_
+
+struct cache_stat_collector {
+        atomic_t cache_hits;
+        atomic_t cache_misses;
+        atomic_t cache_bypass_hits;
+        atomic_t cache_bypass_misses;
+        atomic_t cache_readaheads;
+        atomic_t cache_miss_collisions;
+        atomic_t sectors_bypassed;
+};
+
+struct cache_stats {
+        struct kobject          kobj;
+
+        unsigned long cache_hits;
+        unsigned long cache_misses;
+        unsigned long cache_bypass_hits;
+        unsigned long cache_bypass_misses;
+        unsigned long cache_readaheads;
+        unsigned long cache_miss_collisions;
+        unsigned long sectors_bypassed;
+
+        unsigned                rescale;
+};
+
+struct cache_accounting {
+        struct closure          cl;
+        struct timer_list       timer;
+        atomic_t                closing;
+
+        struct cache_stat_collector collector;
+
+        struct cache_stats total;
+        struct cache_stats five_minute;
+        struct cache_stats hour;
+        struct cache_stats day;
+};
+
+struct search;
+
+void bch_cache_accounting_init(struct cache_accounting *acc,
+                               struct closure *parent);
+
+int bch_cache_accounting_add_kobjs(struct cache_accounting *acc,
+                                   struct kobject *parent);
+
+void bch_cache_accounting_clear(struct cache_accounting *acc);
+
+void bch_cache_accounting_destroy(struct cache_accounting *acc);
+
+void bch_mark_cache_accounting(struct search *s, bool hit, bool bypass);
+void bch_mark_cache_readahead(struct search *s);
+void bch_mark_cache_miss_collision(struct search *s);
+void bch_mark_sectors_bypassed(struct search *s, int sectors);
+
+#endif /* _BCACHE_STATS_H_ */
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
new file mode 100644
index 000000000000..31ef47f1f3b6
--- /dev/null
+++ b/drivers/md/bcache/super.c
@@ -0,0 +1,1941 @@
+/*
+ * bcache setup/teardown code, and some metadata io - read a superblock and
+ * figure out what to do with it.
+ *
+ * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
+ * Copyright 2012 Google, Inc.
+ */
+
+#include "bcache.h"
+#include "btree.h"
+#include "debug.h"
+#include "request.h"
+
+#include <linux/buffer_head.h>
+#include <linux/debugfs.h>
+#include <linux/genhd.h>
+#include <linux/module.h>
+#include <linux/random.h>
+#include <linux/reboot.h>
+#include <linux/sysfs.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Kent Overstreet <kent.overstreet@gmail.com>");
+
+static const char bcache_magic[] = {
+        0xc6, 0x85, 0x73, 0xf6, 0x4e, 0x1a, 0x45, 0xca,
+        0x82, 0x65, 0xf5, 0x7f, 0x48, 0xba, 0x6d, 0x81
+};
+
+static const char invalid_uuid[] = {
+        0xa0, 0x3e, 0xf8, 0xed, 0x3e, 0xe1, 0xb8, 0x78,
+        0xc8, 0x50, 0xfc, 0x5e, 0xcb, 0x16, 0xcd, 0x99
+};
+
+/* Default is -1; we skip past it for struct cached_dev's cache mode */
+const char * const bch_cache_modes[] = {
+        "default",
+        "writethrough",
+        "writeback",
+        "writearound",
+        "none",
+        NULL
+};
+
+struct uuid_entry_v0 {
+        uint8_t         uuid[16];
+        uint8_t         label[32];
+        uint32_t        first_reg;
+        uint32_t        last_reg;
+        uint32_t        invalidated;
+        uint32_t        pad;
+};
+
+static struct kobject *bcache_kobj;
+struct mutex bch_register_lock;
+LIST_HEAD(bch_cache_sets);
+static LIST_HEAD(uncached_devices);
+
+static int bcache_major, bcache_minor;
+static wait_queue_head_t unregister_wait;
+struct workqueue_struct *bcache_wq;
+
+#define BTREE_MAX_PAGES         (256 * 1024 / PAGE_SIZE)
+
+static void bio_split_pool_free(struct bio_split_pool *p)
+{
+        if (p->bio_split)
+                bioset_free(p->bio_split);
+
+}
+
+static int bio_split_pool_init(struct bio_split_pool *p)
+{
+        p->bio_split = bioset_create(4, 0);
+        if (!p->bio_split)
+                return -ENOMEM;
+
+        p->bio_split_hook = mempool_create_kmalloc_pool(4,
+                                sizeof(struct bio_split_hook));
+        if (!p->bio_split_hook)
+                return -ENOMEM;
+
+        return 0;
+}
+
+/* Superblock */
+
+static const char *read_super(struct cache_sb *sb, struct block_device *bdev,
+                              struct page **res)
+{
+        const char *err;
+        struct cache_sb *s;
+        struct buffer_head *bh = __bread(bdev, 1, SB_SIZE);
+        unsigned i;
+
+        if (!bh)
+                return "IO error";
+
+        s = (struct cache_sb *) bh->b_data;
+
+        sb->offset              = le64_to_cpu(s->offset);
+        sb->version             = le64_to_cpu(s->version);
+
+        memcpy(sb->magic,       s->magic, 16);
+        memcpy(sb->uuid,        s->uuid, 16);
+        memcpy(sb->set_uuid,    s->set_uuid, 16);
+        memcpy(sb->label,       s->label, SB_LABEL_SIZE);
+
+        sb->flags               = le64_to_cpu(s->flags);
+        sb->seq                 = le64_to_cpu(s->seq);
+
+        sb->nbuckets            = le64_to_cpu(s->nbuckets);
+        sb->block_size          = le16_to_cpu(s->block_size);
+        sb->bucket_size         = le16_to_cpu(s->bucket_size);
+
+        sb->nr_in_set           = le16_to_cpu(s->nr_in_set);
+        sb->nr_this_dev         = le16_to_cpu(s->nr_this_dev);
+        sb->last_mount          = le32_to_cpu(s->last_mount);
+
+        sb->first_bucket        = le16_to_cpu(s->first_bucket);
+        sb->keys                = le16_to_cpu(s->keys);
+
+        for (i = 0; i < SB_JOURNAL_BUCKETS; i++)
+                sb->d[i] = le64_to_cpu(s->d[i]);
+
+        pr_debug("read sb version %llu, flags %llu, seq %llu, journal size %u",
+                 sb->version, sb->flags, sb->seq, sb->keys);
+
+        err = "Not a bcache superblock";
+        if (sb->offset != SB_SECTOR)
+                goto err;
+
+        if (memcmp(sb->magic, bcache_magic, 16))
+                goto err;
+
+        err = "Too many journal buckets";
+        if (sb->keys > SB_JOURNAL_BUCKETS)
+                goto err;
+
+        err = "Bad checksum";
+        if (s->csum != csum_set(s))
+                goto err;
+
+        err = "Bad UUID";
+        if (is_zero(sb->uuid, 16))
+                goto err;
+
+        err = "Unsupported superblock version";
+        if (sb->version > BCACHE_SB_VERSION)
+                goto err;
+
+        err = "Bad block/bucket size";
+        if (!is_power_of_2(sb->block_size) || sb->block_size > PAGE_SECTORS ||
+            !is_power_of_2(sb->bucket_size) || sb->bucket_size < PAGE_SECTORS)
+                goto err;
+
+        err = "Too many buckets";
+        if (sb->nbuckets > LONG_MAX)
+                goto err;
+
+        err = "Not enough buckets";
+        if (sb->nbuckets < 1 << 7)
+                goto err;
+
+        err = "Invalid superblock: device too small";
+        if (get_capacity(bdev->bd_disk) < sb->bucket_size * sb->nbuckets)
+                goto err;
+
+        if (sb->version == CACHE_BACKING_DEV)
+                goto out;
+
+        err = "Bad UUID";
+        if (is_zero(sb->set_uuid, 16))
+                goto err;
+
+        err = "Bad cache device number in set";
+        if (!sb->nr_in_set ||
+            sb->nr_in_set <= sb->nr_this_dev ||
+            sb->nr_in_set > MAX_CACHES_PER_SET)
+                goto err;
+
+        err = "Journal buckets not sequential";
+        for (i = 0; i < sb->keys; i++)
+                if (sb->d[i] != sb->first_bucket + i)
+                        goto err;
+
+        err = "Too many journal buckets";
+        if (sb->first_bucket + sb->keys > sb->nbuckets)
+                goto err;
+
+        err = "Invalid superblock: first bucket comes before end of super";
+        if (sb->first_bucket * sb->bucket_size < 16)
+                goto err;
+out:
+        sb->last_mount = get_seconds();
+        err = NULL;
+
+        get_page(bh->b_page);
+        *res = bh->b_page;
+err:
+        put_bh(bh);
+        return err;
+}
+
+static void write_bdev_super_endio(struct bio *bio, int error)
+{
+        struct cached_dev *dc = bio->bi_private;
+        /* XXX: error checking */
+
+        closure_put(&dc->sb_write.cl);
+}
+
+static void __write_super(struct cache_sb *sb, struct bio *bio)
+{
+        struct cache_sb *out = page_address(bio->bi_io_vec[0].bv_page);
+        unsigned i;
+
+        bio->bi_sector  = SB_SECTOR;
+        bio->bi_rw      = REQ_SYNC|REQ_META;
+        bio->bi_size    = SB_SIZE;
+        bio_map(bio, NULL);
+
+        out->offset             = cpu_to_le64(sb->offset);
+        out->version            = cpu_to_le64(sb->version);
+
+        memcpy(out->uuid,       sb->uuid, 16);
+        memcpy(out->set_uuid,   sb->set_uuid, 16);
+        memcpy(out->label,      sb->label, SB_LABEL_SIZE);
+
+        out->flags              = cpu_to_le64(sb->flags);
+        out->seq                = cpu_to_le64(sb->seq);
+
+        out->last_mount         = cpu_to_le32(sb->last_mount);
+        out->first_bucket       = cpu_to_le16(sb->first_bucket);
+        out->keys               = cpu_to_le16(sb->keys);
+
+        for (i = 0; i < sb->keys; i++)
+                out->d[i] = cpu_to_le64(sb->d[i]);
+
+        out->csum = csum_set(out);
+
+        pr_debug("ver %llu, flags %llu, seq %llu",
+                 sb->version, sb->flags, sb->seq);
+
+        submit_bio(REQ_WRITE, bio);
+}
+
+void bch_write_bdev_super(struct cached_dev *dc, struct closure *parent)
+{
+        struct closure *cl = &dc->sb_write.cl;
+        struct bio *bio = &dc->sb_bio;
+
+        closure_lock(&dc->sb_write, parent);
+
+        bio_reset(bio);
+        bio->bi_bdev    = dc->bdev;
+        bio->bi_end_io  = write_bdev_super_endio;
+        bio->bi_private = dc;
+
+        closure_get(cl);
+        __write_super(&dc->sb, bio);
+
+        closure_return(cl);
+}
+
+static void write_super_endio(struct bio *bio, int error)
+{
+        struct cache *ca = bio->bi_private;
+
+        bch_count_io_errors(ca, error, "writing superblock");
+        closure_put(&ca->set->sb_write.cl);
+}
+
+void bcache_write_super(struct cache_set *c)
+{
+        struct closure *cl = &c->sb_write.cl;
+        struct cache *ca;
+        unsigned i;
+
+        closure_lock(&c->sb_write, &c->cl);
+
+        c->sb.seq++;
+
+        for_each_cache(ca, c, i) {
+                struct bio *bio = &ca->sb_bio;
+
+                ca->sb.version          = BCACHE_SB_VERSION;
+                ca->sb.seq              = c->sb.seq;
+                ca->sb.last_mount       = c->sb.last_mount;
+
+                SET_CACHE_SYNC(&ca->sb, CACHE_SYNC(&c->sb));
+
+                bio_reset(bio);
+                bio->bi_bdev    = ca->bdev;
+                bio->bi_end_io  = write_super_endio;
+                bio->bi_private = ca;
+
+                closure_get(cl);
+                __write_super(&ca->sb, bio);
+        }
+
+        closure_return(cl);
+}
+
+/* UUID io */
+
+static void uuid_endio(struct bio *bio, int error)
+{
+        struct closure *cl = bio->bi_private;
+        struct cache_set *c = container_of(cl, struct cache_set, uuid_write.cl);
+
+        cache_set_err_on(error, c, "accessing uuids");
+        bch_bbio_free(bio, c);
+        closure_put(cl);
+}
+
+static void uuid_io(struct cache_set *c, unsigned long rw,
+                    struct bkey *k, struct closure *parent)
+{
+        struct closure *cl = &c->uuid_write.cl;
+        struct uuid_entry *u;
+        unsigned i;
+
+        BUG_ON(!parent);
+        closure_lock(&c->uuid_write, parent);
+
+        for (i = 0; i < KEY_PTRS(k); i++) {
+                struct bio *bio = bch_bbio_alloc(c);
+
+                bio->bi_rw      = REQ_SYNC|REQ_META|rw;
+                bio->bi_size    = KEY_SIZE(k) << 9;
+
+                bio->bi_end_io  = uuid_endio;
+                bio->bi_private = cl;
+                bio_map(bio, c->uuids);
+
+                bch_submit_bbio(bio, c, k, i);
+
+                if (!(rw & WRITE))
+                        break;
+        }
+
+        pr_debug("%s UUIDs at %s", rw & REQ_WRITE ? "wrote" : "read",
+                 pkey(&c->uuid_bucket));
+
+        for (u = c->uuids; u < c->uuids + c->nr_uuids; u++)
+                if (!is_zero(u->uuid, 16))
+                        pr_debug("Slot %zi: %pU: %s: 1st: %u last: %u inv: %u",
+                                 u - c->uuids, u->uuid, u->label,
+                                 u->first_reg, u->last_reg, u->invalidated);
+
+        closure_return(cl);
+}
+
+static char *uuid_read(struct cache_set *c, struct jset *j, struct closure *cl)
+{
+        struct bkey *k = &j->uuid_bucket;
+
+        if (__bch_ptr_invalid(c, 1, k))
+                return "bad uuid pointer";
+
+        bkey_copy(&c->uuid_bucket, k);
+        uuid_io(c, READ_SYNC, k, cl);
+
+        if (j->version < BCACHE_JSET_VERSION_UUIDv1) {
+                struct uuid_entry_v0    *u0 = (void *) c->uuids;
+                struct uuid_entry       *u1 = (void *) c->uuids;
+                int i;
+
+                closure_sync(cl);
+
+                /*
+                 * Since the new uuid entry is bigger than the old, we have to
+                 * convert starting at the highest memory address and work down
+                 * in order to do it in place
+                 */
+
+                for (i = c->nr_uuids - 1;
+                     i >= 0;
+                     --i) {
+                        memcpy(u1[i].uuid,      u0[i].uuid, 16);
+                        memcpy(u1[i].label,     u0[i].label, 32);
+
+                        u1[i].first_reg         = u0[i].first_reg;
+                        u1[i].last_reg          = u0[i].last_reg;
+                        u1[i].invalidated       = u0[i].invalidated;
+
+                        u1[i].flags     = 0;
+                        u1[i].sectors   = 0;
+                }
+        }
+
+        return NULL;
+}
+
+static int __uuid_write(struct cache_set *c)
+{
+        BKEY_PADDED(key) k;
+        struct closure cl;
+        closure_init_stack(&cl);
+
+        lockdep_assert_held(&bch_register_lock);
+
+        if (bch_bucket_alloc_set(c, WATERMARK_METADATA, &k.key, 1, &cl))
+                return 1;
+
+        SET_KEY_SIZE(&k.key, c->sb.bucket_size);
+        uuid_io(c, REQ_WRITE, &k.key, &cl);
+        closure_sync(&cl);
+
+        bkey_copy(&c->uuid_bucket, &k.key);
+        __bkey_put(c, &k.key);
+        return 0;
+}
+
+int bch_uuid_write(struct cache_set *c)
+{
+        int ret = __uuid_write(c);
+
+        if (!ret)
+                bch_journal_meta(c, NULL);
+
+        return ret;
+}
+
+static struct uuid_entry *uuid_find(struct cache_set *c, const char *uuid)
+{
+        struct uuid_entry *u;
+
+        for (u = c->uuids;
+             u < c->uuids + c->nr_uuids; u++)
+                if (!memcmp(u->uuid, uuid, 16))
+                        return u;
+
+        return NULL;
+}
+
+static struct uuid_entry *uuid_find_empty(struct cache_set *c)
+{
+        static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
+        return uuid_find(c, zero_uuid);
+}
+
+/*
+ * Bucket priorities/gens:
+ *
+ * For each bucket, we store on disk its
+   * 8 bit gen
+   * 16 bit priority
+ *
+ * See alloc.c for an explanation of the gen. The priority is used to implement
+ * lru (and in the future other) cache replacement policies; for most purposes
+ * it's just an opaque integer.
+ *
+ * The gens and the priorities don't have a whole lot to do with each other, and
+ * it's actually the gens that must be written out at specific times - it's no
+ * big deal if the priorities don't get written, if we lose them we just reuse
+ * buckets in suboptimal order.
+ *
+ * On disk they're stored in a packed array, and in as many buckets are required
+ * to fit them all. The buckets we use to store them form a list; the journal
+ * header points to the first bucket, the first bucket points to the second
+ * bucket, et cetera.
+ *
+ * This code is used by the allocation code; periodically (whenever it runs out
+ * of buckets to allocate from) the allocation code will invalidate some
+ * buckets, but it can't use those buckets until their new gens are safely on
+ * disk.
+ */
+
+static void prio_endio(struct bio *bio, int error)
+{
+        struct cache *ca = bio->bi_private;
+
+        cache_set_err_on(error, ca->set, "accessing priorities");
+        bch_bbio_free(bio, ca->set);
+        closure_put(&ca->prio);
+}
+
+static void prio_io(struct cache *ca, uint64_t bucket, unsigned long rw)
+{
+        struct closure *cl = &ca->prio;
+        struct bio *bio = bch_bbio_alloc(ca->set);
+
+        closure_init_stack(cl);
+
+        bio->bi_sector  = bucket * ca->sb.bucket_size;
+        bio->bi_bdev    = ca->bdev;
+        bio->bi_rw      = REQ_SYNC|REQ_META|rw;
+        bio->bi_size    = bucket_bytes(ca);
+
+        bio->bi_end_io  = prio_endio;
+        bio->bi_private = ca;
+        bio_map(bio, ca->disk_buckets);
+
+        closure_bio_submit(bio, &ca->prio, ca);
+        closure_sync(cl);
+}
+
+#define buckets_free(c) "free %zu, free_inc %zu, unused %zu",           \
+        fifo_used(&c->free), fifo_used(&c->free_inc), fifo_used(&c->unused)
+
+void bch_prio_write(struct cache *ca)
+{
+        int i;
+        struct bucket *b;
+        struct closure cl;
+
+        closure_init_stack(&cl);
+
+        lockdep_assert_held(&ca->set->bucket_lock);
+
+        for (b = ca->buckets;
+             b < ca->buckets + ca->sb.nbuckets; b++)
+                b->disk_gen = b->gen;
+
+        ca->disk_buckets->seq++;
+
+        atomic_long_add(ca->sb.bucket_size * prio_buckets(ca),
+                        &ca->meta_sectors_written);
+
+        pr_debug("free %zu, free_inc %zu, unused %zu", fifo_used(&ca->free),
+                 fifo_used(&ca->free_inc), fifo_used(&ca->unused));
+        blktrace_msg(ca, "Starting priorities: " buckets_free(ca));
+
+        for (i = prio_buckets(ca) - 1; i >= 0; --i) {
+                long bucket;
+                struct prio_set *p = ca->disk_buckets;
+                struct bucket_disk *d = p->data, *end = d + prios_per_bucket(ca);
+
+                for (b = ca->buckets + i * prios_per_bucket(ca);
+                     b < ca->buckets + ca->sb.nbuckets && d < end;
+                     b++, d++) {
+                        d->prio = cpu_to_le16(b->prio);
+                        d->gen = b->gen;
+                }
+
+                p->next_bucket  = ca->prio_buckets[i + 1];
+                p->magic        = pset_magic(ca);
+                p->csum         = crc64(&p->magic, bucket_bytes(ca) - 8);
+
+                bucket = bch_bucket_alloc(ca, WATERMARK_PRIO, &cl);
+                BUG_ON(bucket == -1);
+
+                mutex_unlock(&ca->set->bucket_lock);
+                prio_io(ca, bucket, REQ_WRITE);
+                mutex_lock(&ca->set->bucket_lock);
+
+                ca->prio_buckets[i] = bucket;
+                atomic_dec_bug(&ca->buckets[bucket].pin);
+        }
+
+        mutex_unlock(&ca->set->bucket_lock);
+
+        bch_journal_meta(ca->set, &cl);
+        closure_sync(&cl);
+
+        mutex_lock(&ca->set->bucket_lock);
+
+        ca->need_save_prio = 0;
+
+        /*
+         * Don't want the old priorities to get garbage collected until after we
+         * finish writing the new ones, and they're journalled
+         */
+        for (i = 0; i < prio_buckets(ca); i++)
+                ca->prio_last_buckets[i] = ca->prio_buckets[i];
+}
+
+static void prio_read(struct cache *ca, uint64_t bucket)
+{
+        struct prio_set *p = ca->disk_buckets;
+        struct bucket_disk *d = p->data + prios_per_bucket(ca), *end = d;
+        struct bucket *b;
+        unsigned bucket_nr = 0;
+
+        for (b = ca->buckets;
+             b < ca->buckets + ca->sb.nbuckets;
+             b++, d++) {
+                if (d == end) {
+                        ca->prio_buckets[bucket_nr] = bucket;
+                        ca->prio_last_buckets[bucket_nr] = bucket;
+                        bucket_nr++;
+
+                        prio_io(ca, bucket, READ_SYNC);
+
+                        if (p->csum != crc64(&p->magic, bucket_bytes(ca) - 8))
+                                pr_warn("bad csum reading priorities");
+
+                        if (p->magic != pset_magic(ca))
+                                pr_warn("bad magic reading priorities");
+
+                        bucket = p->next_bucket;
+                        d = p->data;
+                }
+
+                b->prio = le16_to_cpu(d->prio);
+                b->gen = b->disk_gen = b->last_gc = b->gc_gen = d->gen;
+        }
+}
+
+/* Bcache device */
+
+static int open_dev(struct block_device *b, fmode_t mode)
+{
+        struct bcache_device *d = b->bd_disk->private_data;
+        if (atomic_read(&d->closing))
+                return -ENXIO;
+
+        closure_get(&d->cl);
+        return 0;
+}
+
+static int release_dev(struct gendisk *b, fmode_t mode)
+{
+        struct bcache_device *d = b->private_data;
+        closure_put(&d->cl);
+        return 0;
+}
+
+static int ioctl_dev(struct block_device *b, fmode_t mode,
+                     unsigned int cmd, unsigned long arg)
+{
+        struct bcache_device *d = b->bd_disk->private_data;
+        return d->ioctl(d, mode, cmd, arg);
+}
+
+static const struct block_device_operations bcache_ops = {
+        .open           = open_dev,
+        .release        = release_dev,
+        .ioctl          = ioctl_dev,
+        .owner          = THIS_MODULE,
+};
+
+void bcache_device_stop(struct bcache_device *d)
+{
+        if (!atomic_xchg(&d->closing, 1))
+                closure_queue(&d->cl);
+}
+
+static void bcache_device_detach(struct bcache_device *d)
+{
+        lockdep_assert_held(&bch_register_lock);
+
+        if (atomic_read(&d->detaching)) {
+                struct uuid_entry *u = d->c->uuids + d->id;
+
+                SET_UUID_FLASH_ONLY(u, 0);
+                memcpy(u->uuid, invalid_uuid, 16);
+                u->invalidated = cpu_to_le32(get_seconds());
+                bch_uuid_write(d->c);
+
+                atomic_set(&d->detaching, 0);
+        }
+
+        d->c->devices[d->id] = NULL;
+        closure_put(&d->c->caching);
+        d->c = NULL;
+}
+
+static void bcache_device_attach(struct bcache_device *d, struct cache_set *c,
+                                 unsigned id)
+{
+        BUG_ON(test_bit(CACHE_SET_STOPPING, &c->flags));
+
+        d->id = id;
+        d->c = c;
+        c->devices[id] = d;
+
+        closure_get(&c->caching);
+}
+
+static void bcache_device_link(struct bcache_device *d, struct cache_set *c,
+                               const char *name)
+{
+        snprintf(d->name, BCACHEDEVNAME_SIZE,
+                 "%s%u", name, d->id);
+
+        WARN(sysfs_create_link(&d->kobj, &c->kobj, "cache") ||
+             sysfs_create_link(&c->kobj, &d->kobj, d->name),
+             "Couldn't create device <-> cache set symlinks");
+}
+
+static void bcache_device_free(struct bcache_device *d)
+{
+        lockdep_assert_held(&bch_register_lock);
+
+        pr_info("%s stopped", d->disk->disk_name);
+
+        if (d->c)
+                bcache_device_detach(d);
+
+        if (d->disk)
+                del_gendisk(d->disk);
+        if (d->disk && d->disk->queue)
+                blk_cleanup_queue(d->disk->queue);
+        if (d->disk)
+                put_disk(d->disk);
+
+        bio_split_pool_free(&d->bio_split_hook);
+        if (d->unaligned_bvec)
+                mempool_destroy(d->unaligned_bvec);
+        if (d->bio_split)
+                bioset_free(d->bio_split);
+
+        closure_debug_destroy(&d->cl);
+}
+
+static int bcache_device_init(struct bcache_device *d, unsigned block_size)
+{
+        struct request_queue *q;
+
+        if (!(d->bio_split = bioset_create(4, offsetof(struct bbio, bio))) ||
+            !(d->unaligned_bvec = mempool_create_kmalloc_pool(1,
+                                sizeof(struct bio_vec) * BIO_MAX_PAGES)) ||
+            bio_split_pool_init(&d->bio_split_hook))
+
+                return -ENOMEM;
+
+        d->disk = alloc_disk(1);
+        if (!d->disk)
+                return -ENOMEM;
+
+        snprintf(d->disk->disk_name, DISK_NAME_LEN, "bcache%i", bcache_minor);
+
+        d->disk->major          = bcache_major;
+        d->disk->first_minor    = bcache_minor++;
+        d->disk->fops           = &bcache_ops;
+        d->disk->private_data   = d;
+
+        q = blk_alloc_queue(GFP_KERNEL);
+        if (!q)
+                return -ENOMEM;
+
+        blk_queue_make_request(q, NULL);
+        d->disk->queue                  = q;
+        q->queuedata                    = d;
+        q->backing_dev_info.congested_data = d;
+        q->limits.max_hw_sectors        = UINT_MAX;
+        q->limits.max_sectors           = UINT_MAX;
+        q->limits.max_segment_size      = UINT_MAX;
+        q->limits.max_segments          = BIO_MAX_PAGES;
+        q->limits.max_discard_sectors   = UINT_MAX;
+        q->limits.io_min                = block_size;
+        q->limits.logical_block_size    = block_size;
+        q->limits.physical_block_size   = block_size;
+        set_bit(QUEUE_FLAG_NONROT,      &d->disk->queue->queue_flags);
+        set_bit(QUEUE_FLAG_DISCARD,     &d->disk->queue->queue_flags);
+
+        return 0;
+}
+
+/* Cached device */
+
+static void calc_cached_dev_sectors(struct cache_set *c)
+{
+        uint64_t sectors = 0;
+        struct cached_dev *dc;
+
+        list_for_each_entry(dc, &c->cached_devs, list)
+                sectors += bdev_sectors(dc->bdev);
+
+        c->cached_dev_sectors = sectors;
+}
+
+void bch_cached_dev_run(struct cached_dev *dc)
+{
+        struct bcache_device *d = &dc->disk;
+
+        if (atomic_xchg(&dc->running, 1))
+                return;
+
+        if (!d->c &&
+            BDEV_STATE(&dc->sb) != BDEV_STATE_NONE) {
+                struct closure cl;
+                closure_init_stack(&cl);
+
+                SET_BDEV_STATE(&dc->sb, BDEV_STATE_STALE);
+                bch_write_bdev_super(dc, &cl);
+                closure_sync(&cl);
+        }
+
+        add_disk(d->disk);
+#if 0
+        char *env[] = { "SYMLINK=label" , NULL };
+        kobject_uevent_env(&disk_to_dev(d->disk)->kobj, KOBJ_CHANGE, env);
+#endif
+        if (sysfs_create_link(&d->kobj, &disk_to_dev(d->disk)->kobj, "dev") ||
+            sysfs_create_link(&disk_to_dev(d->disk)->kobj, &d->kobj, "bcache"))
+                pr_debug("error creating sysfs link");
+}
+
+static void cached_dev_detach_finish(struct work_struct *w)
+{
+        struct cached_dev *dc = container_of(w, struct cached_dev, detach);
+        char buf[BDEVNAME_SIZE];
+        struct closure cl;
+        closure_init_stack(&cl);
+
+        BUG_ON(!atomic_read(&dc->disk.detaching));
+        BUG_ON(atomic_read(&dc->count));
+
+        sysfs_remove_link(&dc->disk.c->kobj, dc->disk.name);
+        sysfs_remove_link(&dc->disk.kobj, "cache");
+
+        mutex_lock(&bch_register_lock);
+
+        memset(&dc->sb.set_uuid, 0, 16);
+        SET_BDEV_STATE(&dc->sb, BDEV_STATE_NONE);
+
+        bch_write_bdev_super(dc, &cl);
+        closure_sync(&cl);
+
+        bcache_device_detach(&dc->disk);
+        list_move(&dc->list, &uncached_devices);
+
+        mutex_unlock(&bch_register_lock);
+
+        pr_info("Caching disabled for %s", bdevname(dc->bdev, buf));
+
+        /* Drop ref we took in cached_dev_detach() */
+        closure_put(&dc->disk.cl);
+}
+
+void bch_cached_dev_detach(struct cached_dev *dc)
+{
+        lockdep_assert_held(&bch_register_lock);
+
+        if (atomic_read(&dc->disk.closing))
+                return;
+
+        if (atomic_xchg(&dc->disk.detaching, 1))
+                return;
+
+        /*
+         * Block the device from being closed and freed until we're finished
+         * detaching
+         */
+        closure_get(&dc->disk.cl);
+
+        bch_writeback_queue(dc);
+        cached_dev_put(dc);
+}
+
+int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c)
+{
+        uint32_t rtime = cpu_to_le32(get_seconds());
+        struct uuid_entry *u;
+        char buf[BDEVNAME_SIZE];
+
+        bdevname(dc->bdev, buf);
+
+        if (memcmp(dc->sb.set_uuid, c->sb.set_uuid, 16))
+                return -ENOENT;
+
+        if (dc->disk.c) {
+                pr_err("Can't attach %s: already attached", buf);
+                return -EINVAL;
+        }
+
+        if (test_bit(CACHE_SET_STOPPING, &c->flags)) {
+                pr_err("Can't attach %s: shutting down", buf);
+                return -EINVAL;
+        }
+
+        if (dc->sb.block_size < c->sb.block_size) {
+                /* Will die */
+                pr_err("Couldn't attach %s: block size "
+                       "less than set's block size", buf);
+                return -EINVAL;
+        }
+
+        u = uuid_find(c, dc->sb.uuid);
+
+        if (u &&
+            (BDEV_STATE(&dc->sb) == BDEV_STATE_STALE ||
+             BDEV_STATE(&dc->sb) == BDEV_STATE_NONE)) {
+                memcpy(u->uuid, invalid_uuid, 16);
+                u->invalidated = cpu_to_le32(get_seconds());
+                u = NULL;
+        }
+
+        if (!u) {
+                if (BDEV_STATE(&dc->sb) == BDEV_STATE_DIRTY) {
+                        pr_err("Couldn't find uuid for %s in set", buf);
+                        return -ENOENT;
+                }
+
+                u = uuid_find_empty(c);
+                if (!u) {
+                        pr_err("Not caching %s, no room for UUID", buf);
+                        return -EINVAL;
+                }
+        }
+
+        /* Deadlocks since we're called via sysfs...
+        sysfs_remove_file(&dc->kobj, &sysfs_attach);
+         */
+
+        if (is_zero(u->uuid, 16)) {
+                struct closure cl;
+                closure_init_stack(&cl);
+
+                memcpy(u->uuid, dc->sb.uuid, 16);
+                memcpy(u->label, dc->sb.label, SB_LABEL_SIZE);
+                u->first_reg = u->last_reg = rtime;
+                bch_uuid_write(c);
+
+                memcpy(dc->sb.set_uuid, c->sb.set_uuid, 16);
+                SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
+
+                bch_write_bdev_super(dc, &cl);
+                closure_sync(&cl);
+        } else {
+                u->last_reg = rtime;
+                bch_uuid_write(c);
+        }
+
+        bcache_device_attach(&dc->disk, c, u - c->uuids);
+        bcache_device_link(&dc->disk, c, "bdev");
+        list_move(&dc->list, &c->cached_devs);
+        calc_cached_dev_sectors(c);
+
+        smp_wmb();
+        /*
+         * dc->c must be set before dc->count != 0 - paired with the mb in
+         * cached_dev_get()
+         */
+        atomic_set(&dc->count, 1);
+
+        if (BDEV_STATE(&dc->sb) == BDEV_STATE_DIRTY) {
+                atomic_set(&dc->has_dirty, 1);
+                atomic_inc(&dc->count);
+                bch_writeback_queue(dc);
+        }
+
+        bch_cached_dev_run(dc);
+
+        pr_info("Caching %s as %s on set %pU",
+                bdevname(dc->bdev, buf), dc->disk.disk->disk_name,
+                dc->disk.c->sb.set_uuid);
+        return 0;
+}
+
+void bch_cached_dev_release(struct kobject *kobj)
+{
+        struct cached_dev *dc = container_of(kobj, struct cached_dev,
+                                             disk.kobj);
+        kfree(dc);
+        module_put(THIS_MODULE);
+}
+
+static void cached_dev_free(struct closure *cl)
+{
+        struct cached_dev *dc = container_of(cl, struct cached_dev, disk.cl);
+
+        cancel_delayed_work_sync(&dc->writeback_rate_update);
+
+        mutex_lock(&bch_register_lock);
+
+        bcache_device_free(&dc->disk);
+        list_del(&dc->list);
+
+        mutex_unlock(&bch_register_lock);
+
+        if (!IS_ERR_OR_NULL(dc->bdev)) {
+                blk_sync_queue(bdev_get_queue(dc->bdev));
+                blkdev_put(dc->bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
+        }
+
+        wake_up(&unregister_wait);
+
+        kobject_put(&dc->disk.kobj);
+}
+
+static void cached_dev_flush(struct closure *cl)
+{
+        struct cached_dev *dc = container_of(cl, struct cached_dev, disk.cl);
+        struct bcache_device *d = &dc->disk;
+
+        bch_cache_accounting_destroy(&dc->accounting);
+        kobject_del(&d->kobj);
+
+        continue_at(cl, cached_dev_free, system_wq);
+}
+
+static int cached_dev_init(struct cached_dev *dc, unsigned block_size)
+{
+        int err;
+        struct io *io;
+
+        closure_init(&dc->disk.cl, NULL);
+        set_closure_fn(&dc->disk.cl, cached_dev_flush, system_wq);
+
+        __module_get(THIS_MODULE);
+        INIT_LIST_HEAD(&dc->list);
+        kobject_init(&dc->disk.kobj, &bch_cached_dev_ktype);
+
+        bch_cache_accounting_init(&dc->accounting, &dc->disk.cl);
+
+        err = bcache_device_init(&dc->disk, block_size);
+        if (err)
+                goto err;
+
+        spin_lock_init(&dc->io_lock);
+        closure_init_unlocked(&dc->sb_write);
+        INIT_WORK(&dc->detach, cached_dev_detach_finish);
+
+        dc->sequential_merge            = true;
+        dc->sequential_cutoff           = 4 << 20;
+
+        INIT_LIST_HEAD(&dc->io_lru);
+        dc->sb_bio.bi_max_vecs  = 1;
+        dc->sb_bio.bi_io_vec    = dc->sb_bio.bi_inline_vecs;
+
+        for (io = dc->io; io < dc->io + RECENT_IO; io++) {
+                list_add(&io->lru, &dc->io_lru);
+                hlist_add_head(&io->hash, dc->io_hash + RECENT_IO);
+        }
+
+        bch_writeback_init_cached_dev(dc);
+        return 0;
+err:
+        bcache_device_stop(&dc->disk);
+        return err;
+}
+
+/* Cached device - bcache superblock */
+
+static const char *register_bdev(struct cache_sb *sb, struct page *sb_page,
+                                 struct block_device *bdev,
+                                 struct cached_dev *dc)
+{
+        char name[BDEVNAME_SIZE];
+        const char *err = "cannot allocate memory";
+        struct gendisk *g;
+        struct cache_set *c;
+
+        if (!dc || cached_dev_init(dc, sb->block_size << 9) != 0)
+                return err;
+
+        memcpy(&dc->sb, sb, sizeof(struct cache_sb));
+        dc->sb_bio.bi_io_vec[0].bv_page = sb_page;
+        dc->bdev = bdev;
+        dc->bdev->bd_holder = dc;
+
+        g = dc->disk.disk;
+
+        set_capacity(g, dc->bdev->bd_part->nr_sects - 16);
+
+        bch_cached_dev_request_init(dc);
+
+        err = "error creating kobject";
+        if (kobject_add(&dc->disk.kobj, &part_to_dev(bdev->bd_part)->kobj,
+                        "bcache"))
+                goto err;
+        if (bch_cache_accounting_add_kobjs(&dc->accounting, &dc->disk.kobj))
+                goto err;
+
+        list_add(&dc->list, &uncached_devices);
+        list_for_each_entry(c, &bch_cache_sets, list)
+                bch_cached_dev_attach(dc, c);
+
+        if (BDEV_STATE(&dc->sb) == BDEV_STATE_NONE ||
+            BDEV_STATE(&dc->sb) == BDEV_STATE_STALE)
+                bch_cached_dev_run(dc);
+
+        return NULL;
+err:
+        kobject_put(&dc->disk.kobj);
+        pr_notice("error opening %s: %s", bdevname(bdev, name), err);
+        /*
+         * Return NULL instead of an error because kobject_put() cleans
+         * everything up
+         */
+        return NULL;
+}
+
+/* Flash only volumes */
+
+void bch_flash_dev_release(struct kobject *kobj)
+{
+        struct bcache_device *d = container_of(kobj, struct bcache_device,
+                                               kobj);
+        kfree(d);
+}
+
+static void flash_dev_free(struct closure *cl)
+{
+        struct bcache_device *d = container_of(cl, struct bcache_device, cl);
+        bcache_device_free(d);
+        kobject_put(&d->kobj);
+}
+
+static void flash_dev_flush(struct closure *cl)
+{
+        struct bcache_device *d = container_of(cl, struct bcache_device, cl);
+
+        sysfs_remove_link(&d->c->kobj, d->name);
+        sysfs_remove_link(&d->kobj, "cache");
+        kobject_del(&d->kobj);
+        continue_at(cl, flash_dev_free, system_wq);
+}
+
+static int flash_dev_run(struct cache_set *c, struct uuid_entry *u)
+{
+        struct bcache_device *d = kzalloc(sizeof(struct bcache_device),
+                                          GFP_KERNEL);
+        if (!d)
+                return -ENOMEM;
+
+        closure_init(&d->cl, NULL);
+        set_closure_fn(&d->cl, flash_dev_flush, system_wq);
+
+        kobject_init(&d->kobj, &bch_flash_dev_ktype);
+
+        if (bcache_device_init(d, block_bytes(c)))
+                goto err;
+
+        bcache_device_attach(d, c, u - c->uuids);
+        set_capacity(d->disk, u->sectors);
+        bch_flash_dev_request_init(d);
+        add_disk(d->disk);
+
+        if (kobject_add(&d->kobj, &disk_to_dev(d->disk)->kobj, "bcache"))
+                goto err;
+
+        bcache_device_link(d, c, "volume");
+
+        return 0;
+err:
+        kobject_put(&d->kobj);
+        return -ENOMEM;
+}
+
+static int flash_devs_run(struct cache_set *c)
+{
+        int ret = 0;
+        struct uuid_entry *u;
+
+        for (u = c->uuids;
+             u < c->uuids + c->nr_uuids && !ret;
+             u++)
+                if (UUID_FLASH_ONLY(u))
+                        ret = flash_dev_run(c, u);
+
+        return ret;
+}
+
+int bch_flash_dev_create(struct cache_set *c, uint64_t size)
+{
+        struct uuid_entry *u;
+
+        if (test_bit(CACHE_SET_STOPPING, &c->flags))
+                return -EINTR;
+
+        u = uuid_find_empty(c);
+        if (!u) {
+                pr_err("Can't create volume, no room for UUID");
+                return -EINVAL;
+        }
+
+        get_random_bytes(u->uuid, 16);
+        memset(u->label, 0, 32);
+        u->first_reg = u->last_reg = cpu_to_le32(get_seconds());
+
+        SET_UUID_FLASH_ONLY(u, 1);
+        u->sectors = size >> 9;
+
+        bch_uuid_write(c);
+
+        return flash_dev_run(c, u);
+}
+
+/* Cache set */
+
+__printf(2, 3)
+bool bch_cache_set_error(struct cache_set *c, const char *fmt, ...)
+{
+        va_list args;
+
+        if (test_bit(CACHE_SET_STOPPING, &c->flags))
+                return false;
+
+        /* XXX: we can be called from atomic context
+        acquire_console_sem();
+        */
+
+        printk(KERN_ERR "bcache: error on %pU: ", c->sb.set_uuid);
+
+        va_start(args, fmt);
+        vprintk(fmt, args);
+        va_end(args);
+
+        printk(", disabling caching\n");
+
+        bch_cache_set_unregister(c);
+        return true;
+}
+
+void bch_cache_set_release(struct kobject *kobj)
+{
+        struct cache_set *c = container_of(kobj, struct cache_set, kobj);
+        kfree(c);
+        module_put(THIS_MODULE);
+}
+
+static void cache_set_free(struct closure *cl)
+{
+        struct cache_set *c = container_of(cl, struct cache_set, cl);
+        struct cache *ca;
+        unsigned i;
+
+        if (!IS_ERR_OR_NULL(c->debug))
+                debugfs_remove(c->debug);
+
+        bch_open_buckets_free(c);
+        bch_btree_cache_free(c);
+        bch_journal_free(c);
+
+        for_each_cache(ca, c, i)
+                if (ca)
+                        kobject_put(&ca->kobj);
+
+        free_pages((unsigned long) c->uuids, ilog2(bucket_pages(c)));
+        free_pages((unsigned long) c->sort, ilog2(bucket_pages(c)));
+
+        kfree(c->fill_iter);
+        if (c->bio_split)
+                bioset_free(c->bio_split);
+        if (c->bio_meta)
+                mempool_destroy(c->bio_meta);
+        if (c->search)
+                mempool_destroy(c->search);
+        kfree(c->devices);
+
+        mutex_lock(&bch_register_lock);
+        list_del(&c->list);
+        mutex_unlock(&bch_register_lock);
+
+        pr_info("Cache set %pU unregistered", c->sb.set_uuid);
+        wake_up(&unregister_wait);
+
+        closure_debug_destroy(&c->cl);
+        kobject_put(&c->kobj);
+}
+
+static void cache_set_flush(struct closure *cl)
+{
+        struct cache_set *c = container_of(cl, struct cache_set, caching);
+        struct btree *b;
+
+        /* Shut down allocator threads */
+        set_bit(CACHE_SET_STOPPING_2, &c->flags);
+        wake_up(&c->alloc_wait);
+
+        bch_cache_accounting_destroy(&c->accounting);
+
+        kobject_put(&c->internal);
+        kobject_del(&c->kobj);
+
+        if (!IS_ERR_OR_NULL(c->root))
+                list_add(&c->root->list, &c->btree_cache);
+
+        /* Should skip this if we're unregistering because of an error */
+        list_for_each_entry(b, &c->btree_cache, list)
+                if (btree_node_dirty(b))
+                        bch_btree_write(b, true, NULL);
+
+        closure_return(cl);
+}
+
+static void __cache_set_unregister(struct closure *cl)
+{
+        struct cache_set *c = container_of(cl, struct cache_set, caching);
+        struct cached_dev *dc, *t;
+        size_t i;
+
+        mutex_lock(&bch_register_lock);
+
+        if (test_bit(CACHE_SET_UNREGISTERING, &c->flags))
+                list_for_each_entry_safe(dc, t, &c->cached_devs, list)
+                        bch_cached_dev_detach(dc);
+
+        for (i = 0; i < c->nr_uuids; i++)
+                if (c->devices[i] && UUID_FLASH_ONLY(&c->uuids[i]))
+                        bcache_device_stop(c->devices[i]);
+
+        mutex_unlock(&bch_register_lock);
+
+        continue_at(cl, cache_set_flush, system_wq);
+}
+
+void bch_cache_set_stop(struct cache_set *c)
+{
+        if (!test_and_set_bit(CACHE_SET_STOPPING, &c->flags))
+                closure_queue(&c->caching);
+}
+
+void bch_cache_set_unregister(struct cache_set *c)
+{
+        set_bit(CACHE_SET_UNREGISTERING, &c->flags);
+        bch_cache_set_stop(c);
+}
+
+#define alloc_bucket_pages(gfp, c)                      \
+        ((void *) __get_free_pages(__GFP_ZERO|gfp, ilog2(bucket_pages(c))))
+
+struct cache_set *bch_cache_set_alloc(struct cache_sb *sb)
+{
+        int iter_size;
+        struct cache_set *c = kzalloc(sizeof(struct cache_set), GFP_KERNEL);
+        if (!c)
+                return NULL;
+
+        __module_get(THIS_MODULE);
+        closure_init(&c->cl, NULL);
+        set_closure_fn(&c->cl, cache_set_free, system_wq);
+
+        closure_init(&c->caching, &c->cl);
+        set_closure_fn(&c->caching, __cache_set_unregister, system_wq);
+
+        /* Maybe create continue_at_noreturn() and use it here? */
+        closure_set_stopped(&c->cl);
+        closure_put(&c->cl);
+
+        kobject_init(&c->kobj, &bch_cache_set_ktype);
+        kobject_init(&c->internal, &bch_cache_set_internal_ktype);
+
+        bch_cache_accounting_init(&c->accounting, &c->cl);
+
+        memcpy(c->sb.set_uuid, sb->set_uuid, 16);
+        c->sb.block_size        = sb->block_size;
+        c->sb.bucket_size       = sb->bucket_size;
+        c->sb.nr_in_set         = sb->nr_in_set;
+        c->sb.last_mount        = sb->last_mount;
+        c->bucket_bits          = ilog2(sb->bucket_size);
+        c->block_bits           = ilog2(sb->block_size);
+        c->nr_uuids             = bucket_bytes(c) / sizeof(struct uuid_entry);
+
+        c->btree_pages          = c->sb.bucket_size / PAGE_SECTORS;
+        if (c->btree_pages > BTREE_MAX_PAGES)
+                c->btree_pages = max_t(int, c->btree_pages / 4,
+                                       BTREE_MAX_PAGES);
+
+        init_waitqueue_head(&c->alloc_wait);
+        mutex_init(&c->bucket_lock);
+        mutex_init(&c->fill_lock);
+        mutex_init(&c->sort_lock);
+        spin_lock_init(&c->sort_time_lock);
+        closure_init_unlocked(&c->sb_write);
+        closure_init_unlocked(&c->uuid_write);
+        spin_lock_init(&c->btree_read_time_lock);
+        bch_moving_init_cache_set(c);
+
+        INIT_LIST_HEAD(&c->list);
+        INIT_LIST_HEAD(&c->cached_devs);
+        INIT_LIST_HEAD(&c->btree_cache);
+        INIT_LIST_HEAD(&c->btree_cache_freeable);
+        INIT_LIST_HEAD(&c->btree_cache_freed);
+        INIT_LIST_HEAD(&c->data_buckets);
+
+        c->search = mempool_create_slab_pool(32, bch_search_cache);
+        if (!c->search)
+                goto err;
+
+        iter_size = (sb->bucket_size / sb->block_size + 1) *
+                sizeof(struct btree_iter_set);
+
+        if (!(c->devices = kzalloc(c->nr_uuids * sizeof(void *), GFP_KERNEL)) ||
+            !(c->bio_meta = mempool_create_kmalloc_pool(2,
+                                sizeof(struct bbio) + sizeof(struct bio_vec) *
+                                bucket_pages(c))) ||
+            !(c->bio_split = bioset_create(4, offsetof(struct bbio, bio))) ||
+            !(c->fill_iter = kmalloc(iter_size, GFP_KERNEL)) ||
+            !(c->sort = alloc_bucket_pages(GFP_KERNEL, c)) ||
+            !(c->uuids = alloc_bucket_pages(GFP_KERNEL, c)) ||
+            bch_journal_alloc(c) ||
+            bch_btree_cache_alloc(c) ||
+            bch_open_buckets_alloc(c))
+                goto err;
+
+        c->fill_iter->size = sb->bucket_size / sb->block_size;
+
+        c->congested_read_threshold_us  = 2000;
+        c->congested_write_threshold_us = 20000;
+        c->error_limit  = 8 << IO_ERROR_SHIFT;
+
+        return c;
+err:
+        bch_cache_set_unregister(c);
+        return NULL;
+}
+
+static void run_cache_set(struct cache_set *c)
+{
+        const char *err = "cannot allocate memory";
+        struct cached_dev *dc, *t;
+        struct cache *ca;
+        unsigned i;
+
+        struct btree_op op;
+        bch_btree_op_init_stack(&op);
+        op.lock = SHRT_MAX;
+
+        for_each_cache(ca, c, i)
+                c->nbuckets += ca->sb.nbuckets;
+
+        if (CACHE_SYNC(&c->sb)) {
+                LIST_HEAD(journal);
+                struct bkey *k;
+                struct jset *j;
+
+                err = "cannot allocate memory for journal";
+                if (bch_journal_read(c, &journal, &op))
+                        goto err;
+
+                pr_debug("btree_journal_read() done");
+
+                err = "no journal entries found";
+                if (list_empty(&journal))
+                        goto err;
+
+                j = &list_entry(journal.prev, struct journal_replay, list)->j;
+
+                err = "IO error reading priorities";
+                for_each_cache(ca, c, i)
+                        prio_read(ca, j->prio_bucket[ca->sb.nr_this_dev]);
+
+                /*
+                 * If prio_read() fails it'll call cache_set_error and we'll
+                 * tear everything down right away, but if we perhaps checked
+                 * sooner we could avoid journal replay.
+                 */
+
+                k = &j->btree_root;
+
+                err = "bad btree root";
+                if (__bch_ptr_invalid(c, j->btree_level + 1, k))
+                        goto err;
+
+                err = "error reading btree root";
+                c->root = bch_btree_node_get(c, k, j->btree_level, &op);
+                if (IS_ERR_OR_NULL(c->root))
+                        goto err;
+
+                list_del_init(&c->root->list);
+                rw_unlock(true, c->root);
+
+                err = uuid_read(c, j, &op.cl);
+                if (err)
+                        goto err;
+
+                err = "error in recovery";
+                if (bch_btree_check(c, &op))
+                        goto err;
+
+                bch_journal_mark(c, &journal);
+                bch_btree_gc_finish(c);
+                pr_debug("btree_check() done");
+
+                /*
+                 * bcache_journal_next() can't happen sooner, or
+                 * btree_gc_finish() will give spurious errors about last_gc >
+                 * gc_gen - this is a hack but oh well.
+                 */
+                bch_journal_next(&c->journal);
+
+                for_each_cache(ca, c, i)
+                        closure_call(&ca->alloc, bch_allocator_thread,
+                                     system_wq, &c->cl);
+
+                /*
+                 * First place it's safe to allocate: btree_check() and
+                 * btree_gc_finish() have to run before we have buckets to
+                 * allocate, and bch_bucket_alloc_set() might cause a journal
+                 * entry to be written so bcache_journal_next() has to be called
+                 * first.
+                 *
+                 * If the uuids were in the old format we have to rewrite them
+                 * before the next journal entry is written:
+                 */
+                if (j->version < BCACHE_JSET_VERSION_UUID)
+                        __uuid_write(c);
+
+                bch_journal_replay(c, &journal, &op);
+        } else {
+                pr_notice("invalidating existing data");
+                /* Don't want invalidate_buckets() to queue a gc yet */
+                closure_lock(&c->gc, NULL);
+
+                for_each_cache(ca, c, i) {
+                        unsigned j;
+
+                        ca->sb.keys = clamp_t(int, ca->sb.nbuckets >> 7,
+                                              2, SB_JOURNAL_BUCKETS);
+
+                        for (j = 0; j < ca->sb.keys; j++)
+                                ca->sb.d[j] = ca->sb.first_bucket + j;
+                }
+
+                bch_btree_gc_finish(c);
+
+                for_each_cache(ca, c, i)
+                        closure_call(&ca->alloc, bch_allocator_thread,
+                                     ca->alloc_workqueue, &c->cl);
+
+                mutex_lock(&c->bucket_lock);
+                for_each_cache(ca, c, i)
+                        bch_prio_write(ca);
+                mutex_unlock(&c->bucket_lock);
+
+                wake_up(&c->alloc_wait);
+
+                err = "cannot allocate new UUID bucket";
+                if (__uuid_write(c))
+                        goto err_unlock_gc;
+
+                err = "cannot allocate new btree root";
+                c->root = bch_btree_node_alloc(c, 0, &op.cl);
+                if (IS_ERR_OR_NULL(c->root))
+                        goto err_unlock_gc;
+
+                bkey_copy_key(&c->root->key, &MAX_KEY);
+                bch_btree_write(c->root, true, &op);
+
+                bch_btree_set_root(c->root);
+                rw_unlock(true, c->root);
+
+                /*
+                 * We don't want to write the first journal entry until
+                 * everything is set up - fortunately journal entries won't be
+                 * written until the SET_CACHE_SYNC() here:
+                 */
+                SET_CACHE_SYNC(&c->sb, true);
+
+                bch_journal_next(&c->journal);
+                bch_journal_meta(c, &op.cl);
+
+                /* Unlock */
+                closure_set_stopped(&c->gc.cl);
+                closure_put(&c->gc.cl);
+        }
+
+        closure_sync(&op.cl);
+        c->sb.last_mount = get_seconds();
+        bcache_write_super(c);
+
+        list_for_each_entry_safe(dc, t, &uncached_devices, list)
+                bch_cached_dev_attach(dc, c);
+
+        flash_devs_run(c);
+
+        return;
+err_unlock_gc:
+        closure_set_stopped(&c->gc.cl);
+        closure_put(&c->gc.cl);
+err:
+        closure_sync(&op.cl);
+        /* XXX: test this, it's broken */
+        bch_cache_set_error(c, err);
+}
+
+static bool can_attach_cache(struct cache *ca, struct cache_set *c)
+{
+        return ca->sb.block_size        == c->sb.block_size &&
+                ca->sb.bucket_size      == c->sb.block_size &&
+                ca->sb.nr_in_set        == c->sb.nr_in_set;
+}
+
+static const char *register_cache_set(struct cache *ca)
+{
+        char buf[12];
+        const char *err = "cannot allocate memory";
+        struct cache_set *c;
+
+        list_for_each_entry(c, &bch_cache_sets, list)
+                if (!memcmp(c->sb.set_uuid, ca->sb.set_uuid, 16)) {
+                        if (c->cache[ca->sb.nr_this_dev])
+                                return "duplicate cache set member";
+
+                        if (!can_attach_cache(ca, c))
+                                return "cache sb does not match set";
+
+                        if (!CACHE_SYNC(&ca->sb))
+                                SET_CACHE_SYNC(&c->sb, false);
+
+                        goto found;
+                }
+
+        c = bch_cache_set_alloc(&ca->sb);
+        if (!c)
+                return err;
+
+        err = "error creating kobject";
+        if (kobject_add(&c->kobj, bcache_kobj, "%pU", c->sb.set_uuid) ||
+            kobject_add(&c->internal, &c->kobj, "internal"))
+                goto err;
+
+        if (bch_cache_accounting_add_kobjs(&c->accounting, &c->kobj))
+                goto err;
+
+        bch_debug_init_cache_set(c);
+
+        list_add(&c->list, &bch_cache_sets);
+found:
+        sprintf(buf, "cache%i", ca->sb.nr_this_dev);
+        if (sysfs_create_link(&ca->kobj, &c->kobj, "set") ||
+            sysfs_create_link(&c->kobj, &ca->kobj, buf))
+                goto err;
+
+        if (ca->sb.seq > c->sb.seq) {
+                c->sb.version           = ca->sb.version;
+                memcpy(c->sb.set_uuid, ca->sb.set_uuid, 16);
+                c->sb.flags             = ca->sb.flags;
+                c->sb.seq               = ca->sb.seq;
+                pr_debug("set version = %llu", c->sb.version);
+        }
+
+        ca->set = c;
+        ca->set->cache[ca->sb.nr_this_dev] = ca;
+        c->cache_by_alloc[c->caches_loaded++] = ca;
+
+        if (c->caches_loaded == c->sb.nr_in_set)
+                run_cache_set(c);
+
+        return NULL;
+err:
+        bch_cache_set_unregister(c);
+        return err;
+}
+
+/* Cache device */
+
+void bch_cache_release(struct kobject *kobj)
+{
+        struct cache *ca = container_of(kobj, struct cache, kobj);
+
+        if (ca->set)
+                ca->set->cache[ca->sb.nr_this_dev] = NULL;
+
+        bch_cache_allocator_exit(ca);
+
+        bio_split_pool_free(&ca->bio_split_hook);
+
+        if (ca->alloc_workqueue)
+                destroy_workqueue(ca->alloc_workqueue);
+
+        free_pages((unsigned long) ca->disk_buckets, ilog2(bucket_pages(ca)));
+        kfree(ca->prio_buckets);
+        vfree(ca->buckets);
+
+        free_heap(&ca->heap);
+        free_fifo(&ca->unused);
+        free_fifo(&ca->free_inc);
+        free_fifo(&ca->free);
+
+        if (ca->sb_bio.bi_inline_vecs[0].bv_page)
+                put_page(ca->sb_bio.bi_io_vec[0].bv_page);
+
+        if (!IS_ERR_OR_NULL(ca->bdev)) {
+                blk_sync_queue(bdev_get_queue(ca->bdev));
+                blkdev_put(ca->bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
+        }
+
+        kfree(ca);
+        module_put(THIS_MODULE);
+}
+
+static int cache_alloc(struct cache_sb *sb, struct cache *ca)
+{
+        size_t free;
+        struct bucket *b;
+
+        if (!ca)
+                return -ENOMEM;
+
+        __module_get(THIS_MODULE);
+        kobject_init(&ca->kobj, &bch_cache_ktype);
+
+        memcpy(&ca->sb, sb, sizeof(struct cache_sb));
+
+        INIT_LIST_HEAD(&ca->discards);
+
+        bio_init(&ca->sb_bio);
+        ca->sb_bio.bi_max_vecs  = 1;
+        ca->sb_bio.bi_io_vec    = ca->sb_bio.bi_inline_vecs;
+
+        bio_init(&ca->journal.bio);
+        ca->journal.bio.bi_max_vecs = 8;
+        ca->journal.bio.bi_io_vec = ca->journal.bio.bi_inline_vecs;
+
+        free = roundup_pow_of_two(ca->sb.nbuckets) >> 9;
+        free = max_t(size_t, free, (prio_buckets(ca) + 8) * 2);
+
+        if (!init_fifo(&ca->free,       free, GFP_KERNEL) ||
+            !init_fifo(&ca->free_inc,   free << 2, GFP_KERNEL) ||
+            !init_fifo(&ca->unused,     free << 2, GFP_KERNEL) ||
+            !init_heap(&ca->heap,       free << 3, GFP_KERNEL) ||
+            !(ca->buckets       = vmalloc(sizeof(struct bucket) *
+                                          ca->sb.nbuckets)) ||
+            !(ca->prio_buckets  = kzalloc(sizeof(uint64_t) * prio_buckets(ca) *
+                                          2, GFP_KERNEL)) ||
+            !(ca->disk_buckets  = alloc_bucket_pages(GFP_KERNEL, ca)) ||
+            !(ca->alloc_workqueue = alloc_workqueue("bch_allocator", 0, 1)) ||
+            bio_split_pool_init(&ca->bio_split_hook))
+                goto err;
+
+        ca->prio_last_buckets = ca->prio_buckets + prio_buckets(ca);
+
+        memset(ca->buckets, 0, ca->sb.nbuckets * sizeof(struct bucket));
+        for_each_bucket(b, ca)
+                atomic_set(&b->pin, 0);
+
+        if (bch_cache_allocator_init(ca))
+                goto err;
+
+        return 0;
+err:
+        kobject_put(&ca->kobj);
+        return -ENOMEM;
+}
+
+static const char *register_cache(struct cache_sb *sb, struct page *sb_page,
+                                  struct block_device *bdev, struct cache *ca)
+{
+        char name[BDEVNAME_SIZE];
+        const char *err = "cannot allocate memory";
+
+        if (cache_alloc(sb, ca) != 0)
+                return err;
+
+        ca->sb_bio.bi_io_vec[0].bv_page = sb_page;
+        ca->bdev = bdev;
+        ca->bdev->bd_holder = ca;
+
+        if (blk_queue_discard(bdev_get_queue(ca->bdev)))
+                ca->discard = CACHE_DISCARD(&ca->sb);
+
+        err = "error creating kobject";
+        if (kobject_add(&ca->kobj, &part_to_dev(bdev->bd_part)->kobj, "bcache"))
+                goto err;
+
+        err = register_cache_set(ca);
+        if (err)
+                goto err;
+
+        pr_info("registered cache device %s", bdevname(bdev, name));
+
+        return NULL;
+err:
+        kobject_put(&ca->kobj);
+        pr_info("error opening %s: %s", bdevname(bdev, name), err);
+        /* Return NULL instead of an error because kobject_put() cleans
+         * everything up
+         */
+        return NULL;
+}
+
+/* Global interfaces/init */
+
+static ssize_t register_bcache(struct kobject *, struct kobj_attribute *,
+                               const char *, size_t);
+
+kobj_attribute_write(register,          register_bcache);
+kobj_attribute_write(register_quiet,    register_bcache);
+
+static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
+                               const char *buffer, size_t size)
+{
+        ssize_t ret = size;
+        const char *err = "cannot allocate memory";
+        char *path = NULL;
+        struct cache_sb *sb = NULL;
+        struct block_device *bdev = NULL;
+        struct page *sb_page = NULL;
+
+        if (!try_module_get(THIS_MODULE))
+                return -EBUSY;
+
+        mutex_lock(&bch_register_lock);
+
+        if (!(path = kstrndup(buffer, size, GFP_KERNEL)) ||
+            !(sb = kmalloc(sizeof(struct cache_sb), GFP_KERNEL)))
+                goto err;
+
+        err = "failed to open device";
+        bdev = blkdev_get_by_path(strim(path),
+                                  FMODE_READ|FMODE_WRITE|FMODE_EXCL,
+                                  sb);
+        if (bdev == ERR_PTR(-EBUSY))
+                err = "device busy";
+
+        if (IS_ERR(bdev) ||
+            set_blocksize(bdev, 4096))
+                goto err;
+
+        err = read_super(sb, bdev, &sb_page);
+        if (err)
+                goto err_close;
+
+        if (sb->version == CACHE_BACKING_DEV) {
+                struct cached_dev *dc = kzalloc(sizeof(*dc), GFP_KERNEL);
+
+                err = register_bdev(sb, sb_page, bdev, dc);
+        } else {
+                struct cache *ca = kzalloc(sizeof(*ca), GFP_KERNEL);
+
+                err = register_cache(sb, sb_page, bdev, ca);
+        }
+
+        if (err) {
+                /* register_(bdev|cache) will only return an error if they
+                 * didn't get far enough to create the kobject - if they did,
+                 * the kobject destructor will do this cleanup.
+                 */
+                put_page(sb_page);
+err_close:
+                blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
+err:
+                if (attr != &ksysfs_register_quiet)
+                        pr_info("error opening %s: %s", path, err);
+                ret = -EINVAL;
+        }
+
+        kfree(sb);
+        kfree(path);
+        mutex_unlock(&bch_register_lock);
+        module_put(THIS_MODULE);
+        return ret;
+}
+
+static int bcache_reboot(struct notifier_block *n, unsigned long code, void *x)
+{
+        if (code == SYS_DOWN ||
+            code == SYS_HALT ||
+            code == SYS_POWER_OFF) {
+                DEFINE_WAIT(wait);
+                unsigned long start = jiffies;
+                bool stopped = false;
+
+                struct cache_set *c, *tc;
+                struct cached_dev *dc, *tdc;
+
+                mutex_lock(&bch_register_lock);
+
+                if (list_empty(&bch_cache_sets) &&
+                    list_empty(&uncached_devices))
+                        goto out;
+
+                pr_info("Stopping all devices:");
+
+                list_for_each_entry_safe(c, tc, &bch_cache_sets, list)
+                        bch_cache_set_stop(c);
+
+                list_for_each_entry_safe(dc, tdc, &uncached_devices, list)
+                        bcache_device_stop(&dc->disk);
+
+                /* What's a condition variable? */
+                while (1) {
+                        long timeout = start + 2 * HZ - jiffies;
+
+                        stopped = list_empty(&bch_cache_sets) &&
+                                list_empty(&uncached_devices);
+
+                        if (timeout < 0 || stopped)
+                                break;
+
+                        prepare_to_wait(&unregister_wait, &wait,
+                                        TASK_UNINTERRUPTIBLE);
+
+                        mutex_unlock(&bch_register_lock);
+                        schedule_timeout(timeout);
+                        mutex_lock(&bch_register_lock);
+                }
+
+                finish_wait(&unregister_wait, &wait);
+
+                if (stopped)
+                        pr_info("All devices stopped");
+                else
+                        pr_notice("Timeout waiting for devices to be closed");
+out:
+                mutex_unlock(&bch_register_lock);
+        }
+
+        return NOTIFY_DONE;
+}
+
+static struct notifier_block reboot = {
+        .notifier_call  = bcache_reboot,
+        .priority       = INT_MAX, /* before any real devices */
+};
+
+static void bcache_exit(void)
+{
+        bch_debug_exit();
+        bch_writeback_exit();
+        bch_request_exit();
+        bch_btree_exit();
+        if (bcache_kobj)
+                kobject_put(bcache_kobj);
+        if (bcache_wq)
+                destroy_workqueue(bcache_wq);
+        unregister_blkdev(bcache_major, "bcache");
+        unregister_reboot_notifier(&reboot);
+}
+
+static int __init bcache_init(void)
+{
+        static const struct attribute *files[] = {
+                &ksysfs_register.attr,
+                &ksysfs_register_quiet.attr,
+                NULL
+        };
+
+        mutex_init(&bch_register_lock);
+        init_waitqueue_head(&unregister_wait);
+        register_reboot_notifier(&reboot);
+
+        bcache_major = register_blkdev(0, "bcache");
+        if (bcache_major < 0)
+                return bcache_major;
+
+        if (!(bcache_wq = create_workqueue("bcache")) ||
+            !(bcache_kobj = kobject_create_and_add("bcache", fs_kobj)) ||
+            sysfs_create_files(bcache_kobj, files) ||
+            bch_btree_init() ||
+            bch_request_init() ||
+            bch_writeback_init() ||
+            bch_debug_init(bcache_kobj))
+                goto err;
+
+        return 0;
+err:
+        bcache_exit();
+        return -ENOMEM;
+}
+
+module_exit(bcache_exit);
+module_init(bcache_init);
diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
new file mode 100644
index 000000000000..5c7e77073b1f
--- /dev/null
+++ b/drivers/md/bcache/sysfs.c
@@ -0,0 +1,817 @@
+/*
+ * bcache sysfs interfaces
+ *
+ * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
+ * Copyright 2012 Google, Inc.
+ */
+
+#include "bcache.h"
+#include "sysfs.h"
+#include "btree.h"
+#include "request.h"
+
+#include <linux/sort.h>
+
+static const char * const cache_replacement_policies[] = {
+        "lru",
+        "fifo",
+        "random",
+        NULL
+};
+
+write_attribute(attach);
+write_attribute(detach);
+write_attribute(unregister);
+write_attribute(stop);
+write_attribute(clear_stats);
+write_attribute(trigger_gc);
+write_attribute(prune_cache);
+write_attribute(flash_vol_create);
+
+read_attribute(bucket_size);
+read_attribute(block_size);
+read_attribute(nbuckets);
+read_attribute(tree_depth);
+read_attribute(root_usage_percent);
+read_attribute(priority_stats);
+read_attribute(btree_cache_size);
+read_attribute(btree_cache_max_chain);
+read_attribute(cache_available_percent);
+read_attribute(written);
+read_attribute(btree_written);
+read_attribute(metadata_written);
+read_attribute(active_journal_entries);
+
+sysfs_time_stats_attribute(btree_gc,    sec, ms);
+sysfs_time_stats_attribute(btree_split, sec, us);
+sysfs_time_stats_attribute(btree_sort,  ms,  us);
+sysfs_time_stats_attribute(btree_read,  ms,  us);
+sysfs_time_stats_attribute(try_harder,  ms,  us);
+
+read_attribute(btree_nodes);
+read_attribute(btree_used_percent);
+read_attribute(average_key_size);
+read_attribute(dirty_data);
+read_attribute(bset_tree_stats);
+
+read_attribute(state);
+read_attribute(cache_read_races);
+read_attribute(writeback_keys_done);
+read_attribute(writeback_keys_failed);
+read_attribute(io_errors);
+read_attribute(congested);
+rw_attribute(congested_read_threshold_us);
+rw_attribute(congested_write_threshold_us);
+
+rw_attribute(sequential_cutoff);
+rw_attribute(sequential_merge);
+rw_attribute(data_csum);
+rw_attribute(cache_mode);
+rw_attribute(writeback_metadata);
+rw_attribute(writeback_running);
+rw_attribute(writeback_percent);
+rw_attribute(writeback_delay);
+rw_attribute(writeback_rate);
+
+rw_attribute(writeback_rate_update_seconds);
+rw_attribute(writeback_rate_d_term);
+rw_attribute(writeback_rate_p_term_inverse);
+rw_attribute(writeback_rate_d_smooth);
+read_attribute(writeback_rate_debug);
+
+rw_attribute(synchronous);
+rw_attribute(journal_delay_ms);
+rw_attribute(discard);
+rw_attribute(running);
+rw_attribute(label);
+rw_attribute(readahead);
+rw_attribute(io_error_limit);
+rw_attribute(io_error_halflife);
+rw_attribute(verify);
+rw_attribute(key_merging_disabled);
+rw_attribute(gc_always_rewrite);
+rw_attribute(freelist_percent);
+rw_attribute(cache_replacement_policy);
+rw_attribute(btree_shrinker_disabled);
+rw_attribute(copy_gc_enabled);
+rw_attribute(size);
+
+SHOW(__bch_cached_dev)
+{
+        struct cached_dev *dc = container_of(kobj, struct cached_dev,
+                                             disk.kobj);
+        const char *states[] = { "no cache", "clean", "dirty", "inconsistent" };
+
+#define var(stat)               (dc->stat)
+
+        if (attr == &sysfs_cache_mode)
+                return snprint_string_list(buf, PAGE_SIZE,
+                                           bch_cache_modes + 1,
+                                           BDEV_CACHE_MODE(&dc->sb));
+
+        sysfs_printf(data_csum,         "%i", dc->disk.data_csum);
+        var_printf(verify,              "%i");
+        var_printf(writeback_metadata,  "%i");
+        var_printf(writeback_running,   "%i");
+        var_print(writeback_delay);
+        var_print(writeback_percent);
+        sysfs_print(writeback_rate,     dc->writeback_rate.rate);
+
+        var_print(writeback_rate_update_seconds);
+        var_print(writeback_rate_d_term);
+        var_print(writeback_rate_p_term_inverse);
+        var_print(writeback_rate_d_smooth);
+
+        if (attr == &sysfs_writeback_rate_debug) {
+                char dirty[20];
+                char derivative[20];
+                char target[20];
+                hprint(dirty,
+                       atomic_long_read(&dc->disk.sectors_dirty) << 9);
+                hprint(derivative,      dc->writeback_rate_derivative << 9);
+                hprint(target,          dc->writeback_rate_target << 9);
+
+                return sprintf(buf,
+                               "rate:\t\t%u\n"
+                               "change:\t\t%i\n"
+                               "dirty:\t\t%s\n"
+                               "derivative:\t%s\n"
+                               "target:\t\t%s\n",
+                               dc->writeback_rate.rate,
+                               dc->writeback_rate_change,
+                               dirty, derivative, target);
+        }
+
+        sysfs_hprint(dirty_data,
+                     atomic_long_read(&dc->disk.sectors_dirty) << 9);
+
+        var_printf(sequential_merge,    "%i");
+        var_hprint(sequential_cutoff);
+        var_hprint(readahead);
+
+        sysfs_print(running,            atomic_read(&dc->running));
+        sysfs_print(state,              states[BDEV_STATE(&dc->sb)]);
+
+        if (attr == &sysfs_label) {
+                memcpy(buf, dc->sb.label, SB_LABEL_SIZE);
+                buf[SB_LABEL_SIZE + 1] = '\0';
+                strcat(buf, "\n");
+                return strlen(buf);
+        }
+
+#undef var
+        return 0;
+}
+SHOW_LOCKED(bch_cached_dev)
+
+STORE(__cached_dev)
+{
+        struct cached_dev *dc = container_of(kobj, struct cached_dev,
+                                             disk.kobj);
+        unsigned v = size;
+        struct cache_set *c;
+
+#define d_strtoul(var)          sysfs_strtoul(var, dc->var)
+#define d_strtoi_h(var)         sysfs_hatoi(var, dc->var)
+
+        sysfs_strtoul(data_csum,        dc->disk.data_csum);
+        d_strtoul(verify);
+        d_strtoul(writeback_metadata);
+        d_strtoul(writeback_running);
+        d_strtoul(writeback_delay);
+        sysfs_strtoul_clamp(writeback_rate,
+                            dc->writeback_rate.rate, 1, 1000000);
+        sysfs_strtoul_clamp(writeback_percent, dc->writeback_percent, 0, 40);
+
+        d_strtoul(writeback_rate_update_seconds);
+        d_strtoul(writeback_rate_d_term);
+        d_strtoul(writeback_rate_p_term_inverse);
+        sysfs_strtoul_clamp(writeback_rate_p_term_inverse,
+                            dc->writeback_rate_p_term_inverse, 1, INT_MAX);
+        d_strtoul(writeback_rate_d_smooth);
+
+        d_strtoul(sequential_merge);
+        d_strtoi_h(sequential_cutoff);
+        d_strtoi_h(readahead);
+
+        if (attr == &sysfs_clear_stats)
+                bch_cache_accounting_clear(&dc->accounting);
+
+        if (attr == &sysfs_running &&
+            strtoul_or_return(buf))
+                bch_cached_dev_run(dc);
+
+        if (attr == &sysfs_cache_mode) {
+                ssize_t v = read_string_list(buf, bch_cache_modes + 1);
+
+                if (v < 0)
+                        return v;
+
+                if ((unsigned) v != BDEV_CACHE_MODE(&dc->sb)) {
+                        SET_BDEV_CACHE_MODE(&dc->sb, v);
+                        bch_write_bdev_super(dc, NULL);
+                }
+        }
+
+        if (attr == &sysfs_label) {
+                memcpy(dc->sb.label, buf, SB_LABEL_SIZE);
+                bch_write_bdev_super(dc, NULL);
+                if (dc->disk.c) {
+                        memcpy(dc->disk.c->uuids[dc->disk.id].label,
+                               buf, SB_LABEL_SIZE);
+                        bch_uuid_write(dc->disk.c);
+                }
+        }
+
+        if (attr == &sysfs_attach) {
+                if (parse_uuid(buf, dc->sb.set_uuid) < 16)
+                        return -EINVAL;
+
+                list_for_each_entry(c, &bch_cache_sets, list) {
+                        v = bch_cached_dev_attach(dc, c);
+                        if (!v)
+                                return size;
+                }
+
+                pr_err("Can't attach %s: cache set not found", buf);
+                size = v;
+        }
+
+        if (attr == &sysfs_detach && dc->disk.c)
+                bch_cached_dev_detach(dc);
+
+        if (attr == &sysfs_stop)
+                bcache_device_stop(&dc->disk);
+
+        return size;
+}
+
+STORE(bch_cached_dev)
+{
+        struct cached_dev *dc = container_of(kobj, struct cached_dev,
+                                             disk.kobj);
+
+        mutex_lock(&bch_register_lock);
+        size = __cached_dev_store(kobj, attr, buf, size);
+
+        if (attr == &sysfs_writeback_running)
+                bch_writeback_queue(dc);
+
+        if (attr == &sysfs_writeback_percent)
+                schedule_delayed_work(&dc->writeback_rate_update,
+                                      dc->writeback_rate_update_seconds * HZ);
+
+        mutex_unlock(&bch_register_lock);
+        return size;
+}
+
+static struct attribute *bch_cached_dev_files[] = {
+        &sysfs_attach,
+        &sysfs_detach,
+        &sysfs_stop,
+#if 0
+        &sysfs_data_csum,
+#endif
+        &sysfs_cache_mode,
+        &sysfs_writeback_metadata,
+        &sysfs_writeback_running,
+        &sysfs_writeback_delay,
+        &sysfs_writeback_percent,
+        &sysfs_writeback_rate,
+        &sysfs_writeback_rate_update_seconds,
+        &sysfs_writeback_rate_d_term,
+        &sysfs_writeback_rate_p_term_inverse,
+        &sysfs_writeback_rate_d_smooth,
+        &sysfs_writeback_rate_debug,
+        &sysfs_dirty_data,
+        &sysfs_sequential_cutoff,
+        &sysfs_sequential_merge,
+        &sysfs_clear_stats,
+        &sysfs_running,
+        &sysfs_state,
+        &sysfs_label,
+        &sysfs_readahead,
+#ifdef CONFIG_BCACHE_DEBUG
+        &sysfs_verify,
+#endif
+        NULL
+};
+KTYPE(bch_cached_dev);
+
+SHOW(bch_flash_dev)
+{
+        struct bcache_device *d = container_of(kobj, struct bcache_device,
+                                               kobj);
+        struct uuid_entry *u = &d->c->uuids[d->id];
+
+        sysfs_printf(data_csum, "%i", d->data_csum);
+        sysfs_hprint(size,      u->sectors << 9);
+
+        if (attr == &sysfs_label) {
+                memcpy(buf, u->label, SB_LABEL_SIZE);
+                buf[SB_LABEL_SIZE + 1] = '\0';
+                strcat(buf, "\n");
+                return strlen(buf);
+        }
+
+        return 0;
+}
+
+STORE(__bch_flash_dev)
+{
+        struct bcache_device *d = container_of(kobj, struct bcache_device,
+                                               kobj);
+        struct uuid_entry *u = &d->c->uuids[d->id];
+
+        sysfs_strtoul(data_csum,        d->data_csum);
+
+        if (attr == &sysfs_size) {
+                uint64_t v;
+                strtoi_h_or_return(buf, v);
+
+                u->sectors = v >> 9;
+                bch_uuid_write(d->c);
+                set_capacity(d->disk, u->sectors);
+        }
+
+        if (attr == &sysfs_label) {
+                memcpy(u->label, buf, SB_LABEL_SIZE);
+                bch_uuid_write(d->c);
+        }
+
+        if (attr == &sysfs_unregister) {
+                atomic_set(&d->detaching, 1);
+                bcache_device_stop(d);
+        }
+
+        return size;
+}
+STORE_LOCKED(bch_flash_dev)
+
+static struct attribute *bch_flash_dev_files[] = {
+        &sysfs_unregister,
+#if 0
+        &sysfs_data_csum,
+#endif
+        &sysfs_label,
+        &sysfs_size,
+        NULL
+};
+KTYPE(bch_flash_dev);
+
+SHOW(__bch_cache_set)
+{
+        unsigned root_usage(struct cache_set *c)
+        {
+                unsigned bytes = 0;
+                struct bkey *k;
+                struct btree *b;
+                struct btree_iter iter;
+
+                goto lock_root;
+
+                do {
+                        rw_unlock(false, b);
+lock_root:
+                        b = c->root;
+                        rw_lock(false, b, b->level);
+                } while (b != c->root);
+
+                for_each_key_filter(b, k, &iter, bch_ptr_bad)
+                        bytes += bkey_bytes(k);
+
+                rw_unlock(false, b);
+
+                return (bytes * 100) / btree_bytes(c);
+        }
+
+        size_t cache_size(struct cache_set *c)
+        {
+                size_t ret = 0;
+                struct btree *b;
+
+                mutex_lock(&c->bucket_lock);
+                list_for_each_entry(b, &c->btree_cache, list)
+                        ret += 1 << (b->page_order + PAGE_SHIFT);
+
+                mutex_unlock(&c->bucket_lock);
+                return ret;
+        }
+
+        unsigned cache_max_chain(struct cache_set *c)
+        {
+                unsigned ret = 0;
+                struct hlist_head *h;
+
+                mutex_lock(&c->bucket_lock);
+
+                for (h = c->bucket_hash;
+                     h < c->bucket_hash + (1 << BUCKET_HASH_BITS);
+                     h++) {
+                        unsigned i = 0;
+                        struct hlist_node *p;
+
+                        hlist_for_each(p, h)
+                                i++;
+
+                        ret = max(ret, i);
+                }
+
+                mutex_unlock(&c->bucket_lock);
+                return ret;
+        }
+
+        unsigned btree_used(struct cache_set *c)
+        {
+                return div64_u64(c->gc_stats.key_bytes * 100,
+                                 (c->gc_stats.nodes ?: 1) * btree_bytes(c));
+        }
+
+        unsigned average_key_size(struct cache_set *c)
+        {
+                return c->gc_stats.nkeys
+                        ? div64_u64(c->gc_stats.data, c->gc_stats.nkeys)
+                        : 0;
+        }
+
+        struct cache_set *c = container_of(kobj, struct cache_set, kobj);
+
+        sysfs_print(synchronous,                CACHE_SYNC(&c->sb));
+        sysfs_print(journal_delay_ms,           c->journal_delay_ms);
+        sysfs_hprint(bucket_size,               bucket_bytes(c));
+        sysfs_hprint(block_size,                block_bytes(c));
+        sysfs_print(tree_depth,                 c->root->level);
+        sysfs_print(root_usage_percent,         root_usage(c));
+
+        sysfs_hprint(btree_cache_size,          cache_size(c));
+        sysfs_print(btree_cache_max_chain,      cache_max_chain(c));
+        sysfs_print(cache_available_percent,    100 - c->gc_stats.in_use);
+
+        sysfs_print_time_stats(&c->btree_gc_time,       btree_gc, sec, ms);
+        sysfs_print_time_stats(&c->btree_split_time,    btree_split, sec, us);
+        sysfs_print_time_stats(&c->sort_time,           btree_sort, ms, us);
+        sysfs_print_time_stats(&c->btree_read_time,     btree_read, ms, us);
+        sysfs_print_time_stats(&c->try_harder_time,     try_harder, ms, us);
+
+        sysfs_print(btree_used_percent, btree_used(c));
+        sysfs_print(btree_nodes,        c->gc_stats.nodes);
+        sysfs_hprint(dirty_data,        c->gc_stats.dirty);
+        sysfs_hprint(average_key_size,  average_key_size(c));
+
+        sysfs_print(cache_read_races,
+                    atomic_long_read(&c->cache_read_races));
+
+        sysfs_print(writeback_keys_done,
+                    atomic_long_read(&c->writeback_keys_done));
+        sysfs_print(writeback_keys_failed,
+                    atomic_long_read(&c->writeback_keys_failed));
+
+        /* See count_io_errors for why 88 */
+        sysfs_print(io_error_halflife,  c->error_decay * 88);
+        sysfs_print(io_error_limit,     c->error_limit >> IO_ERROR_SHIFT);
+
+        sysfs_hprint(congested,
+                     ((uint64_t) bch_get_congested(c)) << 9);
+        sysfs_print(congested_read_threshold_us,
+                    c->congested_read_threshold_us);
+        sysfs_print(congested_write_threshold_us,
+                    c->congested_write_threshold_us);
+
+        sysfs_print(active_journal_entries,     fifo_used(&c->journal.pin));
+        sysfs_printf(verify,                    "%i", c->verify);
+        sysfs_printf(key_merging_disabled,      "%i", c->key_merging_disabled);
+        sysfs_printf(gc_always_rewrite,         "%i", c->gc_always_rewrite);
+        sysfs_printf(btree_shrinker_disabled,   "%i", c->shrinker_disabled);
+        sysfs_printf(copy_gc_enabled,           "%i", c->copy_gc_enabled);
+
+        if (attr == &sysfs_bset_tree_stats)
+                return bch_bset_print_stats(c, buf);
+
+        return 0;
+}
+SHOW_LOCKED(bch_cache_set)
+
+STORE(__bch_cache_set)
+{
+        struct cache_set *c = container_of(kobj, struct cache_set, kobj);
+
+        if (attr == &sysfs_unregister)
+                bch_cache_set_unregister(c);
+
+        if (attr == &sysfs_stop)
+                bch_cache_set_stop(c);
+
+        if (attr == &sysfs_synchronous) {
+                bool sync = strtoul_or_return(buf);
+
+                if (sync != CACHE_SYNC(&c->sb)) {
+                        SET_CACHE_SYNC(&c->sb, sync);
+                        bcache_write_super(c);
+                }
+        }
+
+        if (attr == &sysfs_flash_vol_create) {
+                int r;
+                uint64_t v;
+                strtoi_h_or_return(buf, v);
+
+                r = bch_flash_dev_create(c, v);
+                if (r)
+                        return r;
+        }
+
+        if (attr == &sysfs_clear_stats) {
+                atomic_long_set(&c->writeback_keys_done,        0);
+                atomic_long_set(&c->writeback_keys_failed,      0);
+
+                memset(&c->gc_stats, 0, sizeof(struct gc_stat));
+                bch_cache_accounting_clear(&c->accounting);
+        }
+
+        if (attr == &sysfs_trigger_gc)
+                bch_queue_gc(c);
+
+        if (attr == &sysfs_prune_cache) {
+                struct shrink_control sc;
+                sc.gfp_mask = GFP_KERNEL;
+                sc.nr_to_scan = strtoul_or_return(buf);
+                c->shrink.shrink(&c->shrink, &sc);
+        }
+
+        sysfs_strtoul(congested_read_threshold_us,
+                      c->congested_read_threshold_us);
+        sysfs_strtoul(congested_write_threshold_us,
+                      c->congested_write_threshold_us);
+
+        if (attr == &sysfs_io_error_limit)
+                c->error_limit = strtoul_or_return(buf) << IO_ERROR_SHIFT;
+
+        /* See count_io_errors() for why 88 */
+        if (attr == &sysfs_io_error_halflife)
+                c->error_decay = strtoul_or_return(buf) / 88;
+
+        sysfs_strtoul(journal_delay_ms,         c->journal_delay_ms);
+        sysfs_strtoul(verify,                   c->verify);
+        sysfs_strtoul(key_merging_disabled,     c->key_merging_disabled);
+        sysfs_strtoul(gc_always_rewrite,        c->gc_always_rewrite);
+        sysfs_strtoul(btree_shrinker_disabled,  c->shrinker_disabled);
+        sysfs_strtoul(copy_gc_enabled,          c->copy_gc_enabled);
+
+        return size;
+}
+STORE_LOCKED(bch_cache_set)
+
+SHOW(bch_cache_set_internal)
+{
+        struct cache_set *c = container_of(kobj, struct cache_set, internal);
+        return bch_cache_set_show(&c->kobj, attr, buf);
+}
+
+STORE(bch_cache_set_internal)
+{
+        struct cache_set *c = container_of(kobj, struct cache_set, internal);
+        return bch_cache_set_store(&c->kobj, attr, buf, size);
+}
+
+static void bch_cache_set_internal_release(struct kobject *k)
+{
+}
+
+static struct attribute *bch_cache_set_files[] = {
+        &sysfs_unregister,
+        &sysfs_stop,
+        &sysfs_synchronous,
+        &sysfs_journal_delay_ms,
+        &sysfs_flash_vol_create,
+
+        &sysfs_bucket_size,
+        &sysfs_block_size,
+        &sysfs_tree_depth,
+        &sysfs_root_usage_percent,
+        &sysfs_btree_cache_size,
+        &sysfs_cache_available_percent,
+
+        &sysfs_average_key_size,
+        &sysfs_dirty_data,
+
+        &sysfs_io_error_limit,
+        &sysfs_io_error_halflife,
+        &sysfs_congested,
+        &sysfs_congested_read_threshold_us,
+        &sysfs_congested_write_threshold_us,
+        &sysfs_clear_stats,
+        NULL
+};
+KTYPE(bch_cache_set);
+
+static struct attribute *bch_cache_set_internal_files[] = {
+        &sysfs_active_journal_entries,
+
+        sysfs_time_stats_attribute_list(btree_gc, sec, ms)
+        sysfs_time_stats_attribute_list(btree_split, sec, us)
+        sysfs_time_stats_attribute_list(btree_sort, ms, us)
+        sysfs_time_stats_attribute_list(btree_read, ms, us)
+        sysfs_time_stats_attribute_list(try_harder, ms, us)
+
+        &sysfs_btree_nodes,
+        &sysfs_btree_used_percent,
+        &sysfs_btree_cache_max_chain,
+
+        &sysfs_bset_tree_stats,
+        &sysfs_cache_read_races,
+        &sysfs_writeback_keys_done,
+        &sysfs_writeback_keys_failed,
+
+        &sysfs_trigger_gc,
+        &sysfs_prune_cache,
+#ifdef CONFIG_BCACHE_DEBUG
+        &sysfs_verify,
+        &sysfs_key_merging_disabled,
+#endif
+        &sysfs_gc_always_rewrite,
+        &sysfs_btree_shrinker_disabled,
+        &sysfs_copy_gc_enabled,
+        NULL
+};
+KTYPE(bch_cache_set_internal);
+
+SHOW(__bch_cache)
+{
+        struct cache *ca = container_of(kobj, struct cache, kobj);
+
+        sysfs_hprint(bucket_size,       bucket_bytes(ca));
+        sysfs_hprint(block_size,        block_bytes(ca));
+        sysfs_print(nbuckets,           ca->sb.nbuckets);
+        sysfs_print(discard,            ca->discard);
+        sysfs_hprint(written, atomic_long_read(&ca->sectors_written) << 9);
+        sysfs_hprint(btree_written,
+                     atomic_long_read(&ca->btree_sectors_written) << 9);
+        sysfs_hprint(metadata_written,
+                     (atomic_long_read(&ca->meta_sectors_written) +
+                      atomic_long_read(&ca->btree_sectors_written)) << 9);
+
+        sysfs_print(io_errors,
+                    atomic_read(&ca->io_errors) >> IO_ERROR_SHIFT);
+
+        sysfs_print(freelist_percent, ca->free.size * 100 /
+                    ((size_t) ca->sb.nbuckets));
+
+        if (attr == &sysfs_cache_replacement_policy)
+                return snprint_string_list(buf, PAGE_SIZE,
+                                           cache_replacement_policies,
+                                           CACHE_REPLACEMENT(&ca->sb));
+
+        if (attr == &sysfs_priority_stats) {
+                int cmp(const void *l, const void *r)
+                {       return *((uint16_t *) r) - *((uint16_t *) l); }
+
+                /* Number of quantiles we compute */
+                const unsigned nq = 31;
+
+                size_t n = ca->sb.nbuckets, i, unused, btree;
+                uint64_t sum = 0;
+                uint16_t q[nq], *p, *cached;
+                ssize_t ret;
+
+                cached = p = vmalloc(ca->sb.nbuckets * sizeof(uint16_t));
+                if (!p)
+                        return -ENOMEM;
+
+                mutex_lock(&ca->set->bucket_lock);
+                for (i = ca->sb.first_bucket; i < n; i++)
+                        p[i] = ca->buckets[i].prio;
+                mutex_unlock(&ca->set->bucket_lock);
+
+                sort(p, n, sizeof(uint16_t), cmp, NULL);
+
+                while (n &&
+                       !cached[n - 1])
+                        --n;
+
+                unused = ca->sb.nbuckets - n;
+
+                while (cached < p + n &&
+                       *cached == BTREE_PRIO)
+                        cached++;
+
+                btree = cached - p;
+                n -= btree;
+
+                for (i = 0; i < n; i++)
+                        sum += INITIAL_PRIO - cached[i];
+
+                if (n)
+                        do_div(sum, n);
+
+                for (i = 0; i < nq; i++)
+                        q[i] = INITIAL_PRIO - cached[n * (i + 1) / (nq + 1)];
+
+                vfree(p);
+
+                ret = snprintf(buf, PAGE_SIZE,
+                               "Unused:         %zu%%\n"
+                               "Metadata:       %zu%%\n"
+                               "Average:        %llu\n"
+                               "Sectors per Q:  %zu\n"
+                               "Quantiles:      [",
+                               unused * 100 / (size_t) ca->sb.nbuckets,
+                               btree * 100 / (size_t) ca->sb.nbuckets, sum,
+                               n * ca->sb.bucket_size / (nq + 1));
+
+                for (i = 0; i < nq && ret < (ssize_t) PAGE_SIZE; i++)
+                        ret += snprintf(buf + ret, PAGE_SIZE - ret,
+                                        i < nq - 1 ? "%u " : "%u]\n", q[i]);
+
+                buf[PAGE_SIZE - 1] = '\0';
+                return ret;
+        }
+
+        return 0;
+}
+SHOW_LOCKED(bch_cache)
+
+STORE(__bch_cache)
+{
+        struct cache *ca = container_of(kobj, struct cache, kobj);
+
+        if (attr == &sysfs_discard) {
+                bool v = strtoul_or_return(buf);
+
+                if (blk_queue_discard(bdev_get_queue(ca->bdev)))
+                        ca->discard = v;
+
+                if (v != CACHE_DISCARD(&ca->sb)) {
+                        SET_CACHE_DISCARD(&ca->sb, v);
+                        bcache_write_super(ca->set);
+                }
+        }
+
+        if (attr == &sysfs_cache_replacement_policy) {
+                ssize_t v = read_string_list(buf, cache_replacement_policies);
+
+                if (v < 0)
+                        return v;
+
+                if ((unsigned) v != CACHE_REPLACEMENT(&ca->sb)) {
+                        mutex_lock(&ca->set->bucket_lock);
+                        SET_CACHE_REPLACEMENT(&ca->sb, v);
+                        mutex_unlock(&ca->set->bucket_lock);
+
+                        bcache_write_super(ca->set);
+                }
+        }
+
+        if (attr == &sysfs_freelist_percent) {
+                DECLARE_FIFO(long, free);
+                long i;
+                size_t p = strtoul_or_return(buf);
+
+                p = clamp_t(size_t,
+                            ((size_t) ca->sb.nbuckets * p) / 100,
+                            roundup_pow_of_two(ca->sb.nbuckets) >> 9,
+                            ca->sb.nbuckets / 2);
+
+                if (!init_fifo_exact(&free, p, GFP_KERNEL))
+                        return -ENOMEM;
+
+                mutex_lock(&ca->set->bucket_lock);
+
+                fifo_move(&free, &ca->free);
+                fifo_swap(&free, &ca->free);
+
+                mutex_unlock(&ca->set->bucket_lock);
+
+                while (fifo_pop(&free, i))
+                        atomic_dec(&ca->buckets[i].pin);
+
+                free_fifo(&free);
+        }
+
+        if (attr == &sysfs_clear_stats) {
+                atomic_long_set(&ca->sectors_written, 0);
+                atomic_long_set(&ca->btree_sectors_written, 0);
+                atomic_long_set(&ca->meta_sectors_written, 0);
+                atomic_set(&ca->io_count, 0);
+                atomic_set(&ca->io_errors, 0);
+        }
+
+        return size;
+}
+STORE_LOCKED(bch_cache)
+
+static struct attribute *bch_cache_files[] = {
+        &sysfs_bucket_size,
+        &sysfs_block_size,
+        &sysfs_nbuckets,
+        &sysfs_priority_stats,
+        &sysfs_discard,
+        &sysfs_written,
+        &sysfs_btree_written,
+        &sysfs_metadata_written,
+        &sysfs_io_errors,
+        &sysfs_clear_stats,
+        &sysfs_freelist_percent,
+        &sysfs_cache_replacement_policy,
+        NULL
+};
+KTYPE(bch_cache);
diff --git a/drivers/md/bcache/sysfs.h b/drivers/md/bcache/sysfs.h
new file mode 100644
index 000000000000..34e4ba1184fe
--- /dev/null
+++ b/drivers/md/bcache/sysfs.h
@@ -0,0 +1,110 @@
+#ifndef _BCACHE_SYSFS_H_
+#define _BCACHE_SYSFS_H_
+
+#define KTYPE(type)                                                     \
+struct kobj_type type ## _ktype = {                                     \
+        .release        = type ## _release,                             \
+        .sysfs_ops      = &((const struct sysfs_ops) {                  \
+                .show   = type ## _show,                                \
+                .store  = type ## _store                                \
+        }),                                                             \
+        .default_attrs  = type ## _files                                \
+}
+
+#define SHOW(fn)                                                        \
+static ssize_t fn ## _show(struct kobject *kobj, struct attribute *attr,\
+                           char *buf)                                   \
+
+#define STORE(fn)                                                       \
+static ssize_t fn ## _store(struct kobject *kobj, struct attribute *attr,\
+                            const char *buf, size_t size)               \
+
+#define SHOW_LOCKED(fn)                                                 \
+SHOW(fn)                                                                \
+{                                                                       \
+        ssize_t ret;                                                    \
+        mutex_lock(&bch_register_lock);                                 \
+        ret = __ ## fn ## _show(kobj, attr, buf);                       \
+        mutex_unlock(&bch_register_lock);                               \
+        return ret;                                                     \
+}
+
+#define STORE_LOCKED(fn)                                                \
+STORE(fn)                                                               \
+{                                                                       \
+        ssize_t ret;                                                    \
+        mutex_lock(&bch_register_lock);                                 \
+        ret = __ ## fn ## _store(kobj, attr, buf, size);                \
+        mutex_unlock(&bch_register_lock);                               \
+        return ret;                                                     \
+}
+
+#define __sysfs_attribute(_name, _mode)                                 \
+        static struct attribute sysfs_##_name =                         \
+                { .name = #_name, .mode = _mode }
+
+#define write_attribute(n)      __sysfs_attribute(n, S_IWUSR)
+#define read_attribute(n)       __sysfs_attribute(n, S_IRUGO)
+#define rw_attribute(n)         __sysfs_attribute(n, S_IRUGO|S_IWUSR)
+
+#define sysfs_printf(file, fmt, ...)                                    \
+do {                                                                    \
+        if (attr == &sysfs_ ## file)                                    \
+                return snprintf(buf, PAGE_SIZE, fmt "\n", __VA_ARGS__); \
+} while (0)
+
+#define sysfs_print(file, var)                                          \
+do {                                                                    \
+        if (attr == &sysfs_ ## file)                                    \
+                return snprint(buf, PAGE_SIZE, var);                    \
+} while (0)
+
+#define sysfs_hprint(file, val)                                         \
+do {                                                                    \
+        if (attr == &sysfs_ ## file) {                                  \
+                ssize_t ret = hprint(buf, val);                         \
+                strcat(buf, "\n");                                      \
+                return ret + 1;                                         \
+        }                                                               \
+} while (0)
+
+#define var_printf(_var, fmt)   sysfs_printf(_var, fmt, var(_var))
+#define var_print(_var)         sysfs_print(_var, var(_var))
+#define var_hprint(_var)        sysfs_hprint(_var, var(_var))
+
+#define sysfs_strtoul(file, var)                                        \
+do {                                                                    \
+        if (attr == &sysfs_ ## file)                                    \
+                return strtoul_safe(buf, var) ?: (ssize_t) size;        \
+} while (0)
+
+#define sysfs_strtoul_clamp(file, var, min, max)                        \
+do {                                                                    \
+        if (attr == &sysfs_ ## file)                                    \
+                return strtoul_safe_clamp(buf, var, min, max)           \
+                        ?: (ssize_t) size;                              \
+} while (0)
+
+#define strtoul_or_return(cp)                                           \
+({                                                                      \
+        unsigned long _v;                                               \
+        int _r = kstrtoul(cp, 10, &_v);                                 \
+        if (_r)                                                         \
+                return _r;                                              \
+        _v;                                                             \
+})
+
+#define strtoi_h_or_return(cp, v)                                       \
+do {                                                                    \
+        int _r = strtoi_h(cp, &v);                                      \
+        if (_r)                                                         \
+                return _r;                                              \
+} while (0)
+
+#define sysfs_hatoi(file, var)                                          \
+do {                                                                    \
+        if (attr == &sysfs_ ## file)                                    \
+                return strtoi_h(buf, &var) ?: (ssize_t) size;           \
+} while (0)
+
+#endif  /* _BCACHE_SYSFS_H_ */
diff --git a/drivers/md/bcache/trace.c b/drivers/md/bcache/trace.c
new file mode 100644
index 000000000000..983f9bb411bc
--- /dev/null
+++ b/drivers/md/bcache/trace.c
@@ -0,0 +1,26 @@
+#include "bcache.h"
+#include "btree.h"
+#include "request.h"
+
+#include <linux/module.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/bcache.h>
+
+EXPORT_TRACEPOINT_SYMBOL_GPL(bcache_request_start);
+EXPORT_TRACEPOINT_SYMBOL_GPL(bcache_request_end);
+EXPORT_TRACEPOINT_SYMBOL_GPL(bcache_passthrough);
+EXPORT_TRACEPOINT_SYMBOL_GPL(bcache_cache_hit);
+EXPORT_TRACEPOINT_SYMBOL_GPL(bcache_cache_miss);
+EXPORT_TRACEPOINT_SYMBOL_GPL(bcache_read_retry);
+EXPORT_TRACEPOINT_SYMBOL_GPL(bcache_writethrough);
+EXPORT_TRACEPOINT_SYMBOL_GPL(bcache_writeback);
+EXPORT_TRACEPOINT_SYMBOL_GPL(bcache_write_skip);
+EXPORT_TRACEPOINT_SYMBOL_GPL(bcache_btree_read);
+EXPORT_TRACEPOINT_SYMBOL_GPL(bcache_btree_write);
+EXPORT_TRACEPOINT_SYMBOL_GPL(bcache_write_dirty);
+EXPORT_TRACEPOINT_SYMBOL_GPL(bcache_read_dirty);
+EXPORT_TRACEPOINT_SYMBOL_GPL(bcache_journal_write);
+EXPORT_TRACEPOINT_SYMBOL_GPL(bcache_cache_insert);
+EXPORT_TRACEPOINT_SYMBOL_GPL(bcache_gc_start);
+EXPORT_TRACEPOINT_SYMBOL_GPL(bcache_gc_end);
diff --git a/drivers/md/bcache/util.c b/drivers/md/bcache/util.c
new file mode 100644
index 000000000000..dcec2e4f84ad
--- /dev/null
+++ b/drivers/md/bcache/util.c
@@ -0,0 +1,389 @@
+/*
+ * random utiility code, for bcache but in theory not specific to bcache
+ *
+ * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
+ * Copyright 2012 Google, Inc.
+ */
+
+#include <linux/bio.h>
+#include <linux/blkdev.h>
+#include <linux/ctype.h>
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/seq_file.h>
+#include <linux/types.h>
+
+#include "util.h"
+
+#define simple_strtoint(c, end, base)   simple_strtol(c, end, base)
+#define simple_strtouint(c, end, base)  simple_strtoul(c, end, base)
+
+#define STRTO_H(name, type)                                     \
+int name ## _h(const char *cp, type *res)                       \
+{                                                               \
+        int u = 0;                                              \
+        char *e;                                                \
+        type i = simple_ ## name(cp, &e, 10);                   \
+                                                                \
+        switch (tolower(*e)) {                                  \
+        default:                                                \
+                return -EINVAL;                                 \
+        case 'y':                                               \
+        case 'z':                                               \
+                u++;                                            \
+        case 'e':                                               \
+                u++;                                            \
+        case 'p':                                               \
+                u++;                                            \
+        case 't':                                               \
+                u++;                                            \
+        case 'g':                                               \
+                u++;                                            \
+        case 'm':                                               \
+                u++;                                            \
+        case 'k':                                               \
+                u++;                                            \
+                if (e++ == cp)                                  \
+                        return -EINVAL;                         \
+        case '\n':                                              \
+        case '\0':                                              \
+                if (*e == '\n')                                 \
+                        e++;                                    \
+        }                                                       \
+                                                                \
+        if (*e)                                                 \
+                return -EINVAL;                                 \
+                                                                \
+        while (u--) {                                           \
+                if ((type) ~0 > 0 &&                            \
+                    (type) ~0 / 1024 <= i)                      \
+                        return -EINVAL;                         \
+                if ((i > 0 && ANYSINT_MAX(type) / 1024 < i) ||  \
+                    (i < 0 && -ANYSINT_MAX(type) / 1024 > i))   \
+                        return -EINVAL;                         \
+                i *= 1024;                                      \
+        }                                                       \
+                                                                \
+        *res = i;                                               \
+        return 0;                                               \
+}                                                               \
+EXPORT_SYMBOL_GPL(name ## _h);
+
+STRTO_H(strtoint, int)
+STRTO_H(strtouint, unsigned int)
+STRTO_H(strtoll, long long)
+STRTO_H(strtoull, unsigned long long)
+
+ssize_t hprint(char *buf, int64_t v)
+{
+        static const char units[] = "?kMGTPEZY";
+        char dec[3] = "";
+        int u, t = 0;
+
+        for (u = 0; v >= 1024 || v <= -1024; u++) {
+                t = v & ~(~0 << 10);
+                v >>= 10;
+        }
+
+        if (!u)
+                return sprintf(buf, "%llu", v);
+
+        if (v < 100 && v > -100)
+                sprintf(dec, ".%i", t / 100);
+
+        return sprintf(buf, "%lli%s%c", v, dec, units[u]);
+}
+EXPORT_SYMBOL_GPL(hprint);
+
+ssize_t snprint_string_list(char *buf, size_t size, const char * const list[],
+                            size_t selected)
+{
+        char *out = buf;
+        size_t i;
+
+        for (i = 0; list[i]; i++)
+                out += snprintf(out, buf + size - out,
+                                i == selected ? "[%s] " : "%s ", list[i]);
+
+        out[-1] = '\n';
+        return out - buf;
+}
+EXPORT_SYMBOL_GPL(snprint_string_list);
+
+ssize_t read_string_list(const char *buf, const char * const list[])
+{
+        size_t i;
+        char *s, *d = kstrndup(buf, PAGE_SIZE - 1, GFP_KERNEL);
+        if (!d)
+                return -ENOMEM;
+
+        s = strim(d);
+
+        for (i = 0; list[i]; i++)
+                if (!strcmp(list[i], s))
+                        break;
+
+        kfree(d);
+
+        if (!list[i])
+                return -EINVAL;
+
+        return i;
+}
+EXPORT_SYMBOL_GPL(read_string_list);
+
+bool is_zero(const char *p, size_t n)
+{
+        size_t i;
+
+        for (i = 0; i < n; i++)
+                if (p[i])
+                        return false;
+        return true;
+}
+EXPORT_SYMBOL_GPL(is_zero);
+
+int parse_uuid(const char *s, char *uuid)
+{
+        size_t i, j, x;
+        memset(uuid, 0, 16);
+
+        for (i = 0, j = 0;
+             i < strspn(s, "-0123456789:ABCDEFabcdef") && j < 32;
+             i++) {
+                x = s[i] | 32;
+
+                switch (x) {
+                case '0'...'9':
+                        x -= '0';
+                        break;
+                case 'a'...'f':
+                        x -= 'a' - 10;
+                        break;
+                default:
+                        continue;
+                }
+
+                if (!(j & 1))
+                        x <<= 4;
+                uuid[j++ >> 1] |= x;
+        }
+        return i;
+}
+EXPORT_SYMBOL_GPL(parse_uuid);
+
+void time_stats_update(struct time_stats *stats, uint64_t start_time)
+{
+        uint64_t now            = local_clock();
+        uint64_t duration       = time_after64(now, start_time)
+                ? now - start_time : 0;
+        uint64_t last           = time_after64(now, stats->last)
+                ? now - stats->last : 0;
+
+        stats->max_duration = max(stats->max_duration, duration);
+
+        if (stats->last) {
+                ewma_add(stats->average_duration, duration, 8, 8);
+
+                if (stats->average_frequency)
+                        ewma_add(stats->average_frequency, last, 8, 8);
+                else
+                        stats->average_frequency  = last << 8;
+        } else {
+                stats->average_duration  = duration << 8;
+        }
+
+        stats->last = now ?: 1;
+}
+EXPORT_SYMBOL_GPL(time_stats_update);
+
+unsigned next_delay(struct ratelimit *d, uint64_t done)
+{
+        uint64_t now = local_clock();
+
+        d->next += div_u64(done, d->rate);
+
+        return time_after64(d->next, now)
+                ? div_u64(d->next - now, NSEC_PER_SEC / HZ)
+                : 0;
+}
+EXPORT_SYMBOL_GPL(next_delay);
+
+void bio_map(struct bio *bio, void *base)
+{
+        size_t size = bio->bi_size;
+        struct bio_vec *bv = bio->bi_io_vec;
+
+        BUG_ON(!bio->bi_size);
+        BUG_ON(bio->bi_vcnt);
+
+        bv->bv_offset = base ? ((unsigned long) base) % PAGE_SIZE : 0;
+        goto start;
+
+        for (; size; bio->bi_vcnt++, bv++) {
+                bv->bv_offset   = 0;
+start:          bv->bv_len      = min_t(size_t, PAGE_SIZE - bv->bv_offset,
+                                        size);
+                if (base) {
+                        bv->bv_page = is_vmalloc_addr(base)
+                                ? vmalloc_to_page(base)
+                                : virt_to_page(base);
+
+                        base += bv->bv_len;
+                }
+
+                size -= bv->bv_len;
+        }
+}
+EXPORT_SYMBOL_GPL(bio_map);
+
+int bio_alloc_pages(struct bio *bio, gfp_t gfp)
+{
+        int i;
+        struct bio_vec *bv;
+
+        bio_for_each_segment(bv, bio, i) {
+                bv->bv_page = alloc_page(gfp);
+                if (!bv->bv_page) {
+                        while (bv-- != bio->bi_io_vec + bio->bi_idx)
+                                __free_page(bv->bv_page);
+                        return -ENOMEM;
+                }
+        }
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(bio_alloc_pages);
+
+/*
+ * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group (Any
+ * use permitted, subject to terms of PostgreSQL license; see.)
+
+ * If we have a 64-bit integer type, then a 64-bit CRC looks just like the
+ * usual sort of implementation. (See Ross Williams' excellent introduction
+ * A PAINLESS GUIDE TO CRC ERROR DETECTION ALGORITHMS, available from
+ * ftp://ftp.rocksoft.com/papers/crc_v3.txt or several other net sites.)
+ * If we have no working 64-bit type, then fake it with two 32-bit registers.
+ *
+ * The present implementation is a normal (not "reflected", in Williams'
+ * terms) 64-bit CRC, using initial all-ones register contents and a final
+ * bit inversion. The chosen polynomial is borrowed from the DLT1 spec
+ * (ECMA-182, available from http://www.ecma.ch/ecma1/STAND/ECMA-182.HTM):
+ *
+ * x^64 + x^62 + x^57 + x^55 + x^54 + x^53 + x^52 + x^47 + x^46 + x^45 +
+ * x^40 + x^39 + x^38 + x^37 + x^35 + x^33 + x^32 + x^31 + x^29 + x^27 +
+ * x^24 + x^23 + x^22 + x^21 + x^19 + x^17 + x^13 + x^12 + x^10 + x^9 +
+ * x^7 + x^4 + x + 1
+*/
+
+static const uint64_t crc_table[256] = {
+        0x0000000000000000, 0x42F0E1EBA9EA3693, 0x85E1C3D753D46D26,
+        0xC711223CFA3E5BB5, 0x493366450E42ECDF, 0x0BC387AEA7A8DA4C,
+        0xCCD2A5925D9681F9, 0x8E224479F47CB76A, 0x9266CC8A1C85D9BE,
+        0xD0962D61B56FEF2D, 0x17870F5D4F51B498, 0x5577EEB6E6BB820B,
+        0xDB55AACF12C73561, 0x99A54B24BB2D03F2, 0x5EB4691841135847,
+        0x1C4488F3E8F96ED4, 0x663D78FF90E185EF, 0x24CD9914390BB37C,
+        0xE3DCBB28C335E8C9, 0xA12C5AC36ADFDE5A, 0x2F0E1EBA9EA36930,
+        0x6DFEFF5137495FA3, 0xAAEFDD6DCD770416, 0xE81F3C86649D3285,
+        0xF45BB4758C645C51, 0xB6AB559E258E6AC2, 0x71BA77A2DFB03177,
+        0x334A9649765A07E4, 0xBD68D2308226B08E, 0xFF9833DB2BCC861D,
+        0x388911E7D1F2DDA8, 0x7A79F00C7818EB3B, 0xCC7AF1FF21C30BDE,
+        0x8E8A101488293D4D, 0x499B3228721766F8, 0x0B6BD3C3DBFD506B,
+        0x854997BA2F81E701, 0xC7B97651866BD192, 0x00A8546D7C558A27,
+        0x4258B586D5BFBCB4, 0x5E1C3D753D46D260, 0x1CECDC9E94ACE4F3,
+        0xDBFDFEA26E92BF46, 0x990D1F49C77889D5, 0x172F5B3033043EBF,
+        0x55DFBADB9AEE082C, 0x92CE98E760D05399, 0xD03E790CC93A650A,
+        0xAA478900B1228E31, 0xE8B768EB18C8B8A2, 0x2FA64AD7E2F6E317,
+        0x6D56AB3C4B1CD584, 0xE374EF45BF6062EE, 0xA1840EAE168A547D,
+        0x66952C92ECB40FC8, 0x2465CD79455E395B, 0x3821458AADA7578F,
+        0x7AD1A461044D611C, 0xBDC0865DFE733AA9, 0xFF3067B657990C3A,
+        0x711223CFA3E5BB50, 0x33E2C2240A0F8DC3, 0xF4F3E018F031D676,
+        0xB60301F359DBE0E5, 0xDA050215EA6C212F, 0x98F5E3FE438617BC,
+        0x5FE4C1C2B9B84C09, 0x1D14202910527A9A, 0x93366450E42ECDF0,
+        0xD1C685BB4DC4FB63, 0x16D7A787B7FAA0D6, 0x5427466C1E109645,
+        0x4863CE9FF6E9F891, 0x0A932F745F03CE02, 0xCD820D48A53D95B7,
+        0x8F72ECA30CD7A324, 0x0150A8DAF8AB144E, 0x43A04931514122DD,
+        0x84B16B0DAB7F7968, 0xC6418AE602954FFB, 0xBC387AEA7A8DA4C0,
+        0xFEC89B01D3679253, 0x39D9B93D2959C9E6, 0x7B2958D680B3FF75,
+        0xF50B1CAF74CF481F, 0xB7FBFD44DD257E8C, 0x70EADF78271B2539,
+        0x321A3E938EF113AA, 0x2E5EB66066087D7E, 0x6CAE578BCFE24BED,
+        0xABBF75B735DC1058, 0xE94F945C9C3626CB, 0x676DD025684A91A1,
+        0x259D31CEC1A0A732, 0xE28C13F23B9EFC87, 0xA07CF2199274CA14,
+        0x167FF3EACBAF2AF1, 0x548F120162451C62, 0x939E303D987B47D7,
+        0xD16ED1D631917144, 0x5F4C95AFC5EDC62E, 0x1DBC74446C07F0BD,
+        0xDAAD56789639AB08, 0x985DB7933FD39D9B, 0x84193F60D72AF34F,
+        0xC6E9DE8B7EC0C5DC, 0x01F8FCB784FE9E69, 0x43081D5C2D14A8FA,
+        0xCD2A5925D9681F90, 0x8FDAB8CE70822903, 0x48CB9AF28ABC72B6,
+        0x0A3B7B1923564425, 0x70428B155B4EAF1E, 0x32B26AFEF2A4998D,
+        0xF5A348C2089AC238, 0xB753A929A170F4AB, 0x3971ED50550C43C1,
+        0x7B810CBBFCE67552, 0xBC902E8706D82EE7, 0xFE60CF6CAF321874,
+        0xE224479F47CB76A0, 0xA0D4A674EE214033, 0x67C58448141F1B86,
+        0x253565A3BDF52D15, 0xAB1721DA49899A7F, 0xE9E7C031E063ACEC,
+        0x2EF6E20D1A5DF759, 0x6C0603E6B3B7C1CA, 0xF6FAE5C07D3274CD,
+        0xB40A042BD4D8425E, 0x731B26172EE619EB, 0x31EBC7FC870C2F78,
+        0xBFC9838573709812, 0xFD39626EDA9AAE81, 0x3A28405220A4F534,
+        0x78D8A1B9894EC3A7, 0x649C294A61B7AD73, 0x266CC8A1C85D9BE0,
+        0xE17DEA9D3263C055, 0xA38D0B769B89F6C6, 0x2DAF4F0F6FF541AC,
+        0x6F5FAEE4C61F773F, 0xA84E8CD83C212C8A, 0xEABE6D3395CB1A19,
+        0x90C79D3FEDD3F122, 0xD2377CD44439C7B1, 0x15265EE8BE079C04,
+        0x57D6BF0317EDAA97, 0xD9F4FB7AE3911DFD, 0x9B041A914A7B2B6E,
+        0x5C1538ADB04570DB, 0x1EE5D94619AF4648, 0x02A151B5F156289C,
+        0x4051B05E58BC1E0F, 0x87409262A28245BA, 0xC5B073890B687329,
+        0x4B9237F0FF14C443, 0x0962D61B56FEF2D0, 0xCE73F427ACC0A965,
+        0x8C8315CC052A9FF6, 0x3A80143F5CF17F13, 0x7870F5D4F51B4980,
+        0xBF61D7E80F251235, 0xFD913603A6CF24A6, 0x73B3727A52B393CC,
+        0x31439391FB59A55F, 0xF652B1AD0167FEEA, 0xB4A25046A88DC879,
+        0xA8E6D8B54074A6AD, 0xEA16395EE99E903E, 0x2D071B6213A0CB8B,
+        0x6FF7FA89BA4AFD18, 0xE1D5BEF04E364A72, 0xA3255F1BE7DC7CE1,
+        0x64347D271DE22754, 0x26C49CCCB40811C7, 0x5CBD6CC0CC10FAFC,
+        0x1E4D8D2B65FACC6F, 0xD95CAF179FC497DA, 0x9BAC4EFC362EA149,
+        0x158E0A85C2521623, 0x577EEB6E6BB820B0, 0x906FC95291867B05,
+        0xD29F28B9386C4D96, 0xCEDBA04AD0952342, 0x8C2B41A1797F15D1,
+        0x4B3A639D83414E64, 0x09CA82762AAB78F7, 0x87E8C60FDED7CF9D,
+        0xC51827E4773DF90E, 0x020905D88D03A2BB, 0x40F9E43324E99428,
+        0x2CFFE7D5975E55E2, 0x6E0F063E3EB46371, 0xA91E2402C48A38C4,
+        0xEBEEC5E96D600E57, 0x65CC8190991CB93D, 0x273C607B30F68FAE,
+        0xE02D4247CAC8D41B, 0xA2DDA3AC6322E288, 0xBE992B5F8BDB8C5C,
+        0xFC69CAB42231BACF, 0x3B78E888D80FE17A, 0x7988096371E5D7E9,
+        0xF7AA4D1A85996083, 0xB55AACF12C735610, 0x724B8ECDD64D0DA5,
+        0x30BB6F267FA73B36, 0x4AC29F2A07BFD00D, 0x08327EC1AE55E69E,
+        0xCF235CFD546BBD2B, 0x8DD3BD16FD818BB8, 0x03F1F96F09FD3CD2,
+        0x41011884A0170A41, 0x86103AB85A2951F4, 0xC4E0DB53F3C36767,
+        0xD8A453A01B3A09B3, 0x9A54B24BB2D03F20, 0x5D45907748EE6495,
+        0x1FB5719CE1045206, 0x919735E51578E56C, 0xD367D40EBC92D3FF,
+        0x1476F63246AC884A, 0x568617D9EF46BED9, 0xE085162AB69D5E3C,
+        0xA275F7C11F7768AF, 0x6564D5FDE549331A, 0x279434164CA30589,
+        0xA9B6706FB8DFB2E3, 0xEB46918411358470, 0x2C57B3B8EB0BDFC5,
+        0x6EA7525342E1E956, 0x72E3DAA0AA188782, 0x30133B4B03F2B111,
+        0xF7021977F9CCEAA4, 0xB5F2F89C5026DC37, 0x3BD0BCE5A45A6B5D,
+        0x79205D0E0DB05DCE, 0xBE317F32F78E067B, 0xFCC19ED95E6430E8,
+        0x86B86ED5267CDBD3, 0xC4488F3E8F96ED40, 0x0359AD0275A8B6F5,
+        0x41A94CE9DC428066, 0xCF8B0890283E370C, 0x8D7BE97B81D4019F,
+        0x4A6ACB477BEA5A2A, 0x089A2AACD2006CB9, 0x14DEA25F3AF9026D,
+        0x562E43B4931334FE, 0x913F6188692D6F4B, 0xD3CF8063C0C759D8,
+        0x5DEDC41A34BBEEB2, 0x1F1D25F19D51D821, 0xD80C07CD676F8394,
+        0x9AFCE626CE85B507
+};
+
+uint64_t crc64_update(uint64_t crc, const void *_data, size_t len)
+{
+        const unsigned char *data = _data;
+
+        while (len--) {
+                int i = ((int) (crc >> 56) ^ *data++) & 0xFF;
+                crc = crc_table[i] ^ (crc << 8);
+        }
+
+        return crc;
+}
+EXPORT_SYMBOL(crc64_update);
+
+uint64_t crc64(const void *data, size_t len)
+{
+        uint64_t crc = 0xffffffffffffffff;
+
+        crc = crc64_update(crc, data, len);
+
+        return crc ^ 0xffffffffffffffff;
+}
+EXPORT_SYMBOL(crc64);
diff --git a/drivers/md/bcache/util.h b/drivers/md/bcache/util.h
new file mode 100644
index 000000000000..56705fdcc149
--- /dev/null
+++ b/drivers/md/bcache/util.h
@@ -0,0 +1,589 @@
+
+#ifndef _BCACHE_UTIL_H
+#define _BCACHE_UTIL_H
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/llist.h>
+#include <linux/ratelimit.h>
+#include <linux/vmalloc.h>
+#include <linux/workqueue.h>
+
+#include "closure.h"
+
+#define PAGE_SECTORS            (PAGE_SIZE / 512)
+
+struct closure;
+
+#include <trace/events/bcache.h>
+
+#ifdef CONFIG_BCACHE_EDEBUG
+
+#define atomic_dec_bug(v)       BUG_ON(atomic_dec_return(v) < 0)
+#define atomic_inc_bug(v, i)    BUG_ON(atomic_inc_return(v) <= i)
+
+#else /* EDEBUG */
+
+#define atomic_dec_bug(v)       atomic_dec(v)
+#define atomic_inc_bug(v, i)    atomic_inc(v)
+
+#endif
+
+#define BITMASK(name, type, field, offset, size)                \
+static inline uint64_t name(const type *k)                      \
+{ return (k->field >> offset) & ~(((uint64_t) ~0) << size); }   \
+                                                                \
+static inline void SET_##name(type *k, uint64_t v)              \
+{                                                               \
+        k->field &= ~(~((uint64_t) ~0 << size) << offset);      \
+        k->field |= v << offset;                                \
+}
+
+#define DECLARE_HEAP(type, name)                                        \
+        struct {                                                        \
+                size_t size, used;                                      \
+                type *data;                                             \
+        } name
+
+#define init_heap(heap, _size, gfp)                                     \
+({                                                                      \
+        size_t _bytes;                                                  \
+        (heap)->used = 0;                                               \
+        (heap)->size = (_size);                                         \
+        _bytes = (heap)->size * sizeof(*(heap)->data);                  \
+        (heap)->data = NULL;                                            \
+        if (_bytes < KMALLOC_MAX_SIZE)                                  \
+                (heap)->data = kmalloc(_bytes, (gfp));                  \
+        if ((!(heap)->data) && ((gfp) & GFP_KERNEL))                    \
+                (heap)->data = vmalloc(_bytes);                         \
+        (heap)->data;                                                   \
+})
+
+#define free_heap(heap)                                                 \
+do {                                                                    \
+        if (is_vmalloc_addr((heap)->data))                              \
+                vfree((heap)->data);                                    \
+        else                                                            \
+                kfree((heap)->data);                                    \
+        (heap)->data = NULL;                                            \
+} while (0)
+
+#define heap_swap(h, i, j)      swap((h)->data[i], (h)->data[j])
+
+#define heap_sift(h, i, cmp)                                            \
+do {                                                                    \
+        size_t _r, _j = i;                                              \
+                                                                        \
+        for (; _j * 2 + 1 < (h)->used; _j = _r) {                       \
+                _r = _j * 2 + 1;                                        \
+                if (_r + 1 < (h)->used &&                               \
+                    cmp((h)->data[_r], (h)->data[_r + 1]))              \
+                        _r++;                                           \
+                                                                        \
+                if (cmp((h)->data[_r], (h)->data[_j]))                  \
+                        break;                                          \
+                heap_swap(h, _r, _j);                                   \
+        }                                                               \
+} while (0)
+
+#define heap_sift_down(h, i, cmp)                                       \
+do {                                                                    \
+        while (i) {                                                     \
+                size_t p = (i - 1) / 2;                                 \
+                if (cmp((h)->data[i], (h)->data[p]))                    \
+                        break;                                          \
+                heap_swap(h, i, p);                                     \
+                i = p;                                                  \
+        }                                                               \
+} while (0)
+
+#define heap_add(h, d, cmp)                                             \
+({                                                                      \
+        bool _r = !heap_full(h);                                        \
+        if (_r) {                                                       \
+                size_t _i = (h)->used++;                                \
+                (h)->data[_i] = d;                                      \
+                                                                        \
+                heap_sift_down(h, _i, cmp);                             \
+                heap_sift(h, _i, cmp);                                  \
+        }                                                               \
+        _r;                                                             \
+})
+
+#define heap_pop(h, d, cmp)                                             \
+({                                                                      \
+        bool _r = (h)->used;                                            \
+        if (_r) {                                                       \
+                (d) = (h)->data[0];                                     \
+                (h)->used--;                                            \
+                heap_swap(h, 0, (h)->used);                             \
+                heap_sift(h, 0, cmp);                                   \
+        }                                                               \
+        _r;                                                             \
+})
+
+#define heap_peek(h)    ((h)->size ? (h)->data[0] : NULL)
+
+#define heap_full(h)    ((h)->used == (h)->size)
+
+#define DECLARE_FIFO(type, name)                                        \
+        struct {                                                        \
+                size_t front, back, size, mask;                         \
+                type *data;                                             \
+        } name
+
+#define fifo_for_each(c, fifo, iter)                                    \
+        for (iter = (fifo)->front;                                      \
+             c = (fifo)->data[iter], iter != (fifo)->back;              \
+             iter = (iter + 1) & (fifo)->mask)
+
+#define __init_fifo(fifo, gfp)                                          \
+({                                                                      \
+        size_t _allocated_size, _bytes;                                 \
+        BUG_ON(!(fifo)->size);                                          \
+                                                                        \
+        _allocated_size = roundup_pow_of_two((fifo)->size + 1);         \
+        _bytes = _allocated_size * sizeof(*(fifo)->data);               \
+                                                                        \
+        (fifo)->mask = _allocated_size - 1;                             \
+        (fifo)->front = (fifo)->back = 0;                               \
+        (fifo)->data = NULL;                                            \
+                                                                        \
+        if (_bytes < KMALLOC_MAX_SIZE)                                  \
+                (fifo)->data = kmalloc(_bytes, (gfp));                  \
+        if ((!(fifo)->data) && ((gfp) & GFP_KERNEL))                    \
+                (fifo)->data = vmalloc(_bytes);                         \
+        (fifo)->data;                                                   \
+})
+
+#define init_fifo_exact(fifo, _size, gfp)                               \
+({                                                                      \
+        (fifo)->size = (_size);                                         \
+        __init_fifo(fifo, gfp);                                         \
+})
+
+#define init_fifo(fifo, _size, gfp)                                     \
+({                                                                      \
+        (fifo)->size = (_size);                                         \
+        if ((fifo)->size > 4)                                           \
+                (fifo)->size = roundup_pow_of_two((fifo)->size) - 1;    \
+        __init_fifo(fifo, gfp);                                         \
+})
+
+#define free_fifo(fifo)                                                 \
+do {                                                                    \
+        if (is_vmalloc_addr((fifo)->data))                              \
+                vfree((fifo)->data);                                    \
+        else                                                            \
+                kfree((fifo)->data);                                    \
+        (fifo)->data = NULL;                                            \
+} while (0)
+
+#define fifo_used(fifo)         (((fifo)->back - (fifo)->front) & (fifo)->mask)
+#define fifo_free(fifo)         ((fifo)->size - fifo_used(fifo))
+
+#define fifo_empty(fifo)        (!fifo_used(fifo))
+#define fifo_full(fifo)         (!fifo_free(fifo))
+
+#define fifo_front(fifo)        ((fifo)->data[(fifo)->front])
+#define fifo_back(fifo)                                                 \
+        ((fifo)->data[((fifo)->back - 1) & (fifo)->mask])
+
+#define fifo_idx(fifo, p)       (((p) - &fifo_front(fifo)) & (fifo)->mask)
+
+#define fifo_push_back(fifo, i)                                         \
+({                                                                      \
+        bool _r = !fifo_full((fifo));                                   \
+        if (_r) {                                                       \
+                (fifo)->data[(fifo)->back++] = (i);                     \
+                (fifo)->back &= (fifo)->mask;                           \
+        }                                                               \
+        _r;                                                             \
+})
+
+#define fifo_pop_front(fifo, i)                                         \
+({                                                                      \
+        bool _r = !fifo_empty((fifo));                                  \
+        if (_r) {                                                       \
+                (i) = (fifo)->data[(fifo)->front++];                    \
+                (fifo)->front &= (fifo)->mask;                          \
+        }                                                               \
+        _r;                                                             \
+})
+
+#define fifo_push_front(fifo, i)                                        \
+({                                                                      \
+        bool _r = !fifo_full((fifo));                                   \
+        if (_r) {                                                       \
+                --(fifo)->front;                                        \
+                (fifo)->front &= (fifo)->mask;                          \
+                (fifo)->data[(fifo)->front] = (i);                      \
+        }                                                               \
+        _r;                                                             \
+})
+
+#define fifo_pop_back(fifo, i)                                          \
+({                                                                      \
+        bool _r = !fifo_empty((fifo));                                  \
+        if (_r) {                                                       \
+                --(fifo)->back;                                         \
+                (fifo)->back &= (fifo)->mask;                           \
+                (i) = (fifo)->data[(fifo)->back]                        \
+        }                                                               \
+        _r;                                                             \
+})
+
+#define fifo_push(fifo, i)      fifo_push_back(fifo, (i))
+#define fifo_pop(fifo, i)       fifo_pop_front(fifo, (i))
+
+#define fifo_swap(l, r)                                                 \
+do {                                                                    \
+        swap((l)->front, (r)->front);                                   \
+        swap((l)->back, (r)->back);                                     \
+        swap((l)->size, (r)->size);                                     \
+        swap((l)->mask, (r)->mask);                                     \
+        swap((l)->data, (r)->data);                                     \
+} while (0)
+
+#define fifo_move(dest, src)                                            \
+do {                                                                    \
+        typeof(*((dest)->data)) _t;                                     \
+        while (!fifo_full(dest) &&                                      \
+               fifo_pop(src, _t))                                       \
+                fifo_push(dest, _t);                                    \
+} while (0)
+
+/*
+ * Simple array based allocator - preallocates a number of elements and you can
+ * never allocate more than that, also has no locking.
+ *
+ * Handy because if you know you only need a fixed number of elements you don't
+ * have to worry about memory allocation failure, and sometimes a mempool isn't
+ * what you want.
+ *
+ * We treat the free elements as entries in a singly linked list, and the
+ * freelist as a stack - allocating and freeing push and pop off the freelist.
+ */
+
+#define DECLARE_ARRAY_ALLOCATOR(type, name, size)                       \
+        struct {                                                        \
+                type    *freelist;                                      \
+                type    data[size];                                     \
+        } name
+
+#define array_alloc(array)                                              \
+({                                                                      \
+        typeof((array)->freelist) _ret = (array)->freelist;             \
+                                                                        \
+        if (_ret)                                                       \
+                (array)->freelist = *((typeof((array)->freelist) *) _ret);\
+                                                                        \
+        _ret;                                                           \
+})
+
+#define array_free(array, ptr)                                          \
+do {                                                                    \
+        typeof((array)->freelist) _ptr = ptr;                           \
+                                                                        \
+        *((typeof((array)->freelist) *) _ptr) = (array)->freelist;      \
+        (array)->freelist = _ptr;                                       \
+} while (0)
+
+#define array_allocator_init(array)                                     \
+do {                                                                    \
+        typeof((array)->freelist) _i;                                   \
+                                                                        \
+        BUILD_BUG_ON(sizeof((array)->data[0]) < sizeof(void *));        \
+        (array)->freelist = NULL;                                       \
+                                                                        \
+        for (_i = (array)->data;                                        \
+             _i < (array)->data + ARRAY_SIZE((array)->data);            \
+             _i++)                                                      \
+                array_free(array, _i);                                  \
+} while (0)
+
+#define array_freelist_empty(array)     ((array)->freelist == NULL)
+
+#define ANYSINT_MAX(t)                                                  \
+        ((((t) 1 << (sizeof(t) * 8 - 2)) - (t) 1) * (t) 2 + (t) 1)
+
+int strtoint_h(const char *, int *);
+int strtouint_h(const char *, unsigned int *);
+int strtoll_h(const char *, long long *);
+int strtoull_h(const char *, unsigned long long *);
+
+static inline int strtol_h(const char *cp, long *res)
+{
+#if BITS_PER_LONG == 32
+        return strtoint_h(cp, (int *) res);
+#else
+        return strtoll_h(cp, (long long *) res);
+#endif
+}
+
+static inline int strtoul_h(const char *cp, long *res)
+{
+#if BITS_PER_LONG == 32
+        return strtouint_h(cp, (unsigned int *) res);
+#else
+        return strtoull_h(cp, (unsigned long long *) res);
+#endif
+}
+
+#define strtoi_h(cp, res)                                               \
+        (__builtin_types_compatible_p(typeof(*res), int)                \
+        ? strtoint_h(cp, (void *) res)                                  \
+        : __builtin_types_compatible_p(typeof(*res), long)              \
+        ? strtol_h(cp, (void *) res)                                    \
+        : __builtin_types_compatible_p(typeof(*res), long long)         \
+        ? strtoll_h(cp, (void *) res)                                   \
+        : __builtin_types_compatible_p(typeof(*res), unsigned int)      \
+        ? strtouint_h(cp, (void *) res)                                 \
+        : __builtin_types_compatible_p(typeof(*res), unsigned long)     \
+        ? strtoul_h(cp, (void *) res)                                   \
+        : __builtin_types_compatible_p(typeof(*res), unsigned long long)\
+        ? strtoull_h(cp, (void *) res) : -EINVAL)
+
+#define strtoul_safe(cp, var)                                           \
+({                                                                      \
+        unsigned long _v;                                               \
+        int _r = kstrtoul(cp, 10, &_v);                                 \
+        if (!_r)                                                        \
+                var = _v;                                               \
+        _r;                                                             \
+})
+
+#define strtoul_safe_clamp(cp, var, min, max)                           \
+({                                                                      \
+        unsigned long _v;                                               \
+        int _r = kstrtoul(cp, 10, &_v);                                 \
+        if (!_r)                                                        \
+                var = clamp_t(typeof(var), _v, min, max);               \
+        _r;                                                             \
+})
+
+#define snprint(buf, size, var)                                         \
+        snprintf(buf, size,                                             \
+                __builtin_types_compatible_p(typeof(var), int)          \
+                     ? "%i\n" :                                         \
+                __builtin_types_compatible_p(typeof(var), unsigned)     \
+                     ? "%u\n" :                                         \
+                __builtin_types_compatible_p(typeof(var), long)         \
+                     ? "%li\n" :                                        \
+                __builtin_types_compatible_p(typeof(var), unsigned long)\
+                     ? "%lu\n" :                                        \
+                __builtin_types_compatible_p(typeof(var), int64_t)      \
+                     ? "%lli\n" :                                       \
+                __builtin_types_compatible_p(typeof(var), uint64_t)     \
+                     ? "%llu\n" :                                       \
+                __builtin_types_compatible_p(typeof(var), const char *) \
+                     ? "%s\n" : "%i\n", var)
+
+ssize_t hprint(char *buf, int64_t v);
+
+bool is_zero(const char *p, size_t n);
+int parse_uuid(const char *s, char *uuid);
+
+ssize_t snprint_string_list(char *buf, size_t size, const char * const list[],
+                            size_t selected);
+
+ssize_t read_string_list(const char *buf, const char * const list[]);
+
+struct time_stats {
+        /*
+         * all fields are in nanoseconds, averages are ewmas stored left shifted
+         * by 8
+         */
+        uint64_t        max_duration;
+        uint64_t        average_duration;
+        uint64_t        average_frequency;
+        uint64_t        last;
+};
+
+void time_stats_update(struct time_stats *stats, uint64_t time);
+
+#define NSEC_PER_ns                     1L
+#define NSEC_PER_us                     NSEC_PER_USEC
+#define NSEC_PER_ms                     NSEC_PER_MSEC
+#define NSEC_PER_sec                    NSEC_PER_SEC
+
+#define __print_time_stat(stats, name, stat, units)                     \
+        sysfs_print(name ## _ ## stat ## _ ## units,                    \
+                    div_u64((stats)->stat >> 8, NSEC_PER_ ## units))
+
+#define sysfs_print_time_stats(stats, name,                             \
+                               frequency_units,                         \
+                               duration_units)                          \
+do {                                                                    \
+        __print_time_stat(stats, name,                                  \
+                          average_frequency,    frequency_units);       \
+        __print_time_stat(stats, name,                                  \
+                          average_duration,     duration_units);        \
+        __print_time_stat(stats, name,                                  \
+                          max_duration,         duration_units);        \
+                                                                        \
+        sysfs_print(name ## _last_ ## frequency_units, (stats)->last    \
+                    ? div_s64(local_clock() - (stats)->last,            \
+                              NSEC_PER_ ## frequency_units)             \
+                    : -1LL);                                            \
+} while (0)
+
+#define sysfs_time_stats_attribute(name,                                \
+                                   frequency_units,                     \
+                                   duration_units)                      \
+read_attribute(name ## _average_frequency_ ## frequency_units);         \
+read_attribute(name ## _average_duration_ ## duration_units);           \
+read_attribute(name ## _max_duration_ ## duration_units);               \
+read_attribute(name ## _last_ ## frequency_units)
+
+#define sysfs_time_stats_attribute_list(name,                           \
+                                        frequency_units,                \
+                                        duration_units)                 \
+&sysfs_ ## name ## _average_frequency_ ## frequency_units,              \
+&sysfs_ ## name ## _average_duration_ ## duration_units,                \
+&sysfs_ ## name ## _max_duration_ ## duration_units,                    \
+&sysfs_ ## name ## _last_ ## frequency_units,
+
+#define ewma_add(ewma, val, weight, factor)                             \
+({                                                                      \
+        (ewma) *= (weight) - 1;                                         \
+        (ewma) += (val) << factor;                                      \
+        (ewma) /= (weight);                                             \
+        (ewma) >> factor;                                               \
+})
+
+struct ratelimit {
+        uint64_t                next;
+        unsigned                rate;
+};
+
+static inline void ratelimit_reset(struct ratelimit *d)
+{
+        d->next = local_clock();
+}
+
+unsigned next_delay(struct ratelimit *d, uint64_t done);
+
+#define __DIV_SAFE(n, d, zero)                                          \
+({                                                                      \
+        typeof(n) _n = (n);                                             \
+        typeof(d) _d = (d);                                             \
+        _d ? _n / _d : zero;                                            \
+})
+
+#define DIV_SAFE(n, d)  __DIV_SAFE(n, d, 0)
+
+#define container_of_or_null(ptr, type, member)                         \
+({                                                                      \
+        typeof(ptr) _ptr = ptr;                                         \
+        _ptr ? container_of(_ptr, type, member) : NULL;                 \
+})
+
+#define RB_INSERT(root, new, member, cmp)                               \
+({                                                                      \
+        __label__ dup;                                                  \
+        struct rb_node **n = &(root)->rb_node, *parent = NULL;          \
+        typeof(new) this;                                               \
+        int res, ret = -1;                                              \
+                                                                        \
+        while (*n) {                                                    \
+                parent = *n;                                            \
+                this = container_of(*n, typeof(*(new)), member);        \
+                res = cmp(new, this);                                   \
+                if (!res)                                               \
+                        goto dup;                                       \
+                n = res < 0                                             \
+                        ? &(*n)->rb_left                                \
+                        : &(*n)->rb_right;                              \
+        }                                                               \
+                                                                        \
+        rb_link_node(&(new)->member, parent, n);                        \
+        rb_insert_color(&(new)->member, root);                          \
+        ret = 0;                                                        \
+dup:                                                                    \
+        ret;                                                            \
+})
+
+#define RB_SEARCH(root, search, member, cmp)                            \
+({                                                                      \
+        struct rb_node *n = (root)->rb_node;                            \
+        typeof(&(search)) this, ret = NULL;                             \
+        int res;                                                        \
+                                                                        \
+        while (n) {                                                     \
+                this = container_of(n, typeof(search), member);         \
+                res = cmp(&(search), this);                             \
+                if (!res) {                                             \
+                        ret = this;                                     \
+                        break;                                          \
+                }                                                       \
+                n = res < 0                                             \
+                        ? n->rb_left                                    \
+                        : n->rb_right;                                  \
+        }                                                               \
+        ret;                                                            \
+})
+
+#define RB_GREATER(root, search, member, cmp)                           \
+({                                                                      \
+        struct rb_node *n = (root)->rb_node;                            \
+        typeof(&(search)) this, ret = NULL;                             \
+        int res;                                                        \
+                                                                        \
+        while (n) {                                                     \
+                this = container_of(n, typeof(search), member);         \
+                res = cmp(&(search), this);                             \
+                if (res < 0) {                                          \
+                        ret = this;                                     \
+                        n = n->rb_left;                                 \
+                } else                                                  \
+                        n = n->rb_right;                                \
+        }                                                               \
+        ret;                                                            \
+})
+
+#define RB_FIRST(root, type, member)                                    \
+        container_of_or_null(rb_first(root), type, member)
+
+#define RB_LAST(root, type, member)                                     \
+        container_of_or_null(rb_last(root), type, member)
+
+#define RB_NEXT(ptr, member)                                            \
+        container_of_or_null(rb_next(&(ptr)->member), typeof(*ptr), member)
+
+#define RB_PREV(ptr, member)                                            \
+        container_of_or_null(rb_prev(&(ptr)->member), typeof(*ptr), member)
+
+/* Does linear interpolation between powers of two */
+static inline unsigned fract_exp_two(unsigned x, unsigned fract_bits)
+{
+        unsigned fract = x & ~(~0 << fract_bits);
+
+        x >>= fract_bits;
+        x   = 1 << x;
+        x  += (x * fract) >> fract_bits;
+
+        return x;
+}
+
+#define bio_end(bio)    ((bio)->bi_sector + bio_sectors(bio))
+
+void bio_map(struct bio *bio, void *base);
+
+int bio_alloc_pages(struct bio *bio, gfp_t gfp);
+
+static inline sector_t bdev_sectors(struct block_device *bdev)
+{
+        return bdev->bd_inode->i_size >> 9;
+}
+
+#define closure_bio_submit(bio, cl, dev)                                \
+do {                                                                    \
+        closure_get(cl);                                                \
+        bch_generic_make_request(bio, &(dev)->bio_split_hook);          \
+} while (0)
+
+uint64_t crc64_update(uint64_t, const void *, size_t);
+uint64_t crc64(const void *, size_t);
+
+#endif /* _BCACHE_UTIL_H */
diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
new file mode 100644
index 000000000000..a80ee5373fd8
--- /dev/null
+++ b/drivers/md/bcache/writeback.c
@@ -0,0 +1,414 @@
+/*
+ * background writeback - scan btree for dirty data and write it to the backing
+ * device
+ *
+ * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
+ * Copyright 2012 Google, Inc.
+ */
+
+#include "bcache.h"
+#include "btree.h"
+#include "debug.h"
+
+static struct workqueue_struct *dirty_wq;
+
+static void read_dirty(struct closure *);
+
+struct dirty_io {
+        struct closure          cl;
+        struct cached_dev       *dc;
+        struct bio              bio;
+};
+
+/* Rate limiting */
+
+static void __update_writeback_rate(struct cached_dev *dc)
+{
+        struct cache_set *c = dc->disk.c;
+        uint64_t cache_sectors = c->nbuckets * c->sb.bucket_size;
+        uint64_t cache_dirty_target =
+                div_u64(cache_sectors * dc->writeback_percent, 100);
+
+        int64_t target = div64_u64(cache_dirty_target * bdev_sectors(dc->bdev),
+                                   c->cached_dev_sectors);
+
+        /* PD controller */
+
+        int change = 0;
+        int64_t error;
+        int64_t dirty = atomic_long_read(&dc->disk.sectors_dirty);
+        int64_t derivative = dirty - dc->disk.sectors_dirty_last;
+
+        dc->disk.sectors_dirty_last = dirty;
+
+        derivative *= dc->writeback_rate_d_term;
+        derivative = clamp(derivative, -dirty, dirty);
+
+        derivative = ewma_add(dc->disk.sectors_dirty_derivative, derivative,
+                              dc->writeback_rate_d_smooth, 0);
+
+        /* Avoid divide by zero */
+        if (!target)
+                goto out;
+
+        error = div64_s64((dirty + derivative - target) << 8, target);
+
+        change = div_s64((dc->writeback_rate.rate * error) >> 8,
+                         dc->writeback_rate_p_term_inverse);
+
+        /* Don't increase writeback rate if the device isn't keeping up */
+        if (change > 0 &&
+            time_after64(local_clock(),
+                         dc->writeback_rate.next + 10 * NSEC_PER_MSEC))
+                change = 0;
+
+        dc->writeback_rate.rate =
+                clamp_t(int64_t, dc->writeback_rate.rate + change,
+                        1, NSEC_PER_MSEC);
+out:
+        dc->writeback_rate_derivative = derivative;
+        dc->writeback_rate_change = change;
+        dc->writeback_rate_target = target;
+
+        schedule_delayed_work(&dc->writeback_rate_update,
+                              dc->writeback_rate_update_seconds * HZ);
+}
+
+static void update_writeback_rate(struct work_struct *work)
+{
+        struct cached_dev *dc = container_of(to_delayed_work(work),
+                                             struct cached_dev,
+                                             writeback_rate_update);
+
+        down_read(&dc->writeback_lock);
+
+        if (atomic_read(&dc->has_dirty) &&
+            dc->writeback_percent)
+                __update_writeback_rate(dc);
+
+        up_read(&dc->writeback_lock);
+}
+
+static unsigned writeback_delay(struct cached_dev *dc, unsigned sectors)
+{
+        if (atomic_read(&dc->disk.detaching) ||
+            !dc->writeback_percent)
+                return 0;
+
+        return next_delay(&dc->writeback_rate, sectors * 10000000ULL);
+}
+
+/* Background writeback */
+
+static bool dirty_pred(struct keybuf *buf, struct bkey *k)
+{
+        return KEY_DIRTY(k);
+}
+
+static void dirty_init(struct keybuf_key *w)
+{
+        struct dirty_io *io = w->private;
+        struct bio *bio = &io->bio;
+
+        bio_init(bio);
+        if (!io->dc->writeback_percent)
+                bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
+
+        bio->bi_size            = KEY_SIZE(&w->key) << 9;
+        bio->bi_max_vecs        = DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS);
+        bio->bi_private         = w;
+        bio->bi_io_vec          = bio->bi_inline_vecs;
+        bio_map(bio, NULL);
+}
+
+static void refill_dirty(struct closure *cl)
+{
+        struct cached_dev *dc = container_of(cl, struct cached_dev,
+                                             writeback.cl);
+        struct keybuf *buf = &dc->writeback_keys;
+        bool searched_from_start = false;
+        struct bkey end = MAX_KEY;
+        SET_KEY_INODE(&end, dc->disk.id);
+
+        if (!atomic_read(&dc->disk.detaching) &&
+            !dc->writeback_running)
+                closure_return(cl);
+
+        down_write(&dc->writeback_lock);
+
+        if (!atomic_read(&dc->has_dirty)) {
+                SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
+                bch_write_bdev_super(dc, NULL);
+
+                up_write(&dc->writeback_lock);
+                closure_return(cl);
+        }
+
+        if (bkey_cmp(&buf->last_scanned, &end) >= 0) {
+                buf->last_scanned = KEY(dc->disk.id, 0, 0);
+                searched_from_start = true;
+        }
+
+        bch_refill_keybuf(dc->disk.c, buf, &end);
+
+        if (bkey_cmp(&buf->last_scanned, &end) >= 0 && searched_from_start) {
+                /* Searched the entire btree  - delay awhile */
+
+                if (RB_EMPTY_ROOT(&buf->keys)) {
+                        atomic_set(&dc->has_dirty, 0);
+                        cached_dev_put(dc);
+                }
+
+                if (!atomic_read(&dc->disk.detaching))
+                        closure_delay(&dc->writeback, dc->writeback_delay * HZ);
+        }
+
+        up_write(&dc->writeback_lock);
+
+        ratelimit_reset(&dc->writeback_rate);
+
+        /* Punt to workqueue only so we don't recurse and blow the stack */
+        continue_at(cl, read_dirty, dirty_wq);
+}
+
+void bch_writeback_queue(struct cached_dev *dc)
+{
+        if (closure_trylock(&dc->writeback.cl, &dc->disk.cl)) {
+                if (!atomic_read(&dc->disk.detaching))
+                        closure_delay(&dc->writeback, dc->writeback_delay * HZ);
+
+                continue_at(&dc->writeback.cl, refill_dirty, dirty_wq);
+        }
+}
+
+void bch_writeback_add(struct cached_dev *dc, unsigned sectors)
+{
+        atomic_long_add(sectors, &dc->disk.sectors_dirty);
+
+        if (!atomic_read(&dc->has_dirty) &&
+            !atomic_xchg(&dc->has_dirty, 1)) {
+                atomic_inc(&dc->count);
+
+                if (BDEV_STATE(&dc->sb) != BDEV_STATE_DIRTY) {
+                        SET_BDEV_STATE(&dc->sb, BDEV_STATE_DIRTY);
+                        /* XXX: should do this synchronously */
+                        bch_write_bdev_super(dc, NULL);
+                }
+
+                bch_writeback_queue(dc);
+
+                if (dc->writeback_percent)
+                        schedule_delayed_work(&dc->writeback_rate_update,
+                                      dc->writeback_rate_update_seconds * HZ);
+        }
+}
+
+/* Background writeback - IO loop */
+
+static void dirty_io_destructor(struct closure *cl)
+{
+        struct dirty_io *io = container_of(cl, struct dirty_io, cl);
+        kfree(io);
+}
+
+static void write_dirty_finish(struct closure *cl)
+{
+        struct dirty_io *io = container_of(cl, struct dirty_io, cl);
+        struct keybuf_key *w = io->bio.bi_private;
+        struct cached_dev *dc = io->dc;
+        struct bio_vec *bv = bio_iovec_idx(&io->bio, io->bio.bi_vcnt);
+
+        while (bv-- != io->bio.bi_io_vec)
+                __free_page(bv->bv_page);
+
+        /* This is kind of a dumb way of signalling errors. */
+        if (KEY_DIRTY(&w->key)) {
+                unsigned i;
+                struct btree_op op;
+                bch_btree_op_init_stack(&op);
+
+                op.type = BTREE_REPLACE;
+                bkey_copy(&op.replace, &w->key);
+
+                SET_KEY_DIRTY(&w->key, false);
+                bch_keylist_add(&op.keys, &w->key);
+
+                for (i = 0; i < KEY_PTRS(&w->key); i++)
+                        atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin);
+
+                pr_debug("clearing %s", pkey(&w->key));
+                bch_btree_insert(&op, dc->disk.c);
+                closure_sync(&op.cl);
+
+                atomic_long_inc(op.insert_collision
+                                ? &dc->disk.c->writeback_keys_failed
+                                : &dc->disk.c->writeback_keys_done);
+        }
+
+        bch_keybuf_del(&dc->writeback_keys, w);
+        atomic_dec_bug(&dc->in_flight);
+
+        closure_wake_up(&dc->writeback_wait);
+
+        closure_return_with_destructor(cl, dirty_io_destructor);
+}
+
+static void dirty_endio(struct bio *bio, int error)
+{
+        struct keybuf_key *w = bio->bi_private;
+        struct dirty_io *io = w->private;
+
+        if (error)
+                SET_KEY_DIRTY(&w->key, false);
+
+        closure_put(&io->cl);
+}
+
+static void write_dirty(struct closure *cl)
+{
+        struct dirty_io *io = container_of(cl, struct dirty_io, cl);
+        struct keybuf_key *w = io->bio.bi_private;
+
+        dirty_init(w);
+        io->bio.bi_rw           = WRITE;
+        io->bio.bi_sector       = KEY_START(&w->key);
+        io->bio.bi_bdev         = io->dc->bdev;
+        io->bio.bi_end_io       = dirty_endio;
+
+        trace_bcache_write_dirty(&io->bio);
+        closure_bio_submit(&io->bio, cl, &io->dc->disk);
+
+        continue_at(cl, write_dirty_finish, dirty_wq);
+}
+
+static void read_dirty_endio(struct bio *bio, int error)
+{
+        struct keybuf_key *w = bio->bi_private;
+        struct dirty_io *io = w->private;
+
+        bch_count_io_errors(PTR_CACHE(io->dc->disk.c, &w->key, 0),
+                            error, "reading dirty data from cache");
+
+        dirty_endio(bio, error);
+}
+
+static void read_dirty_submit(struct closure *cl)
+{
+        struct dirty_io *io = container_of(cl, struct dirty_io, cl);
+
+        trace_bcache_read_dirty(&io->bio);
+        closure_bio_submit(&io->bio, cl, &io->dc->disk);
+
+        continue_at(cl, write_dirty, dirty_wq);
+}
+
+static void read_dirty(struct closure *cl)
+{
+        struct cached_dev *dc = container_of(cl, struct cached_dev,
+                                             writeback.cl);
+        unsigned delay = writeback_delay(dc, 0);
+        struct keybuf_key *w;
+        struct dirty_io *io;
+
+        /*
+         * XXX: if we error, background writeback just spins. Should use some
+         * mempools.
+         */
+
+        while (1) {
+                w = bch_keybuf_next(&dc->writeback_keys);
+                if (!w)
+                        break;
+
+                BUG_ON(ptr_stale(dc->disk.c, &w->key, 0));
+
+                if (delay > 0 &&
+                    (KEY_START(&w->key) != dc->last_read ||
+                     jiffies_to_msecs(delay) > 50)) {
+                        w->private = NULL;
+
+                        closure_delay(&dc->writeback, delay);
+                        continue_at(cl, read_dirty, dirty_wq);
+                }
+
+                dc->last_read   = KEY_OFFSET(&w->key);
+
+                io = kzalloc(sizeof(struct dirty_io) + sizeof(struct bio_vec)
+                             * DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS),
+                             GFP_KERNEL);
+                if (!io)
+                        goto err;
+
+                w->private      = io;
+                io->dc          = dc;
+
+                dirty_init(w);
+                io->bio.bi_sector       = PTR_OFFSET(&w->key, 0);
+                io->bio.bi_bdev         = PTR_CACHE(dc->disk.c,
+                                                    &w->key, 0)->bdev;
+                io->bio.bi_rw           = READ;
+                io->bio.bi_end_io       = read_dirty_endio;
+
+                if (bio_alloc_pages(&io->bio, GFP_KERNEL))
+                        goto err_free;
+
+                pr_debug("%s", pkey(&w->key));
+
+                closure_call(&io->cl, read_dirty_submit, NULL, &dc->disk.cl);
+
+                delay = writeback_delay(dc, KEY_SIZE(&w->key));
+
+                atomic_inc(&dc->in_flight);
+
+                if (!closure_wait_event(&dc->writeback_wait, cl,
+                                        atomic_read(&dc->in_flight) < 64))
+                        continue_at(cl, read_dirty, dirty_wq);
+        }
+
+        if (0) {
+err_free:
+                kfree(w->private);
+err:
+                bch_keybuf_del(&dc->writeback_keys, w);
+        }
+
+        refill_dirty(cl);
+}
+
+void bch_writeback_init_cached_dev(struct cached_dev *dc)
+{
+        closure_init_unlocked(&dc->writeback);
+        init_rwsem(&dc->writeback_lock);
+
+        bch_keybuf_init(&dc->writeback_keys, dirty_pred);
+
+        dc->writeback_metadata          = true;
+        dc->writeback_running           = true;
+        dc->writeback_percent           = 10;
+        dc->writeback_delay             = 30;
+        dc->writeback_rate.rate         = 1024;
+
+        dc->writeback_rate_update_seconds = 30;
+        dc->writeback_rate_d_term       = 16;
+        dc->writeback_rate_p_term_inverse = 64;
+        dc->writeback_rate_d_smooth     = 8;
+
+        INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate);
+        schedule_delayed_work(&dc->writeback_rate_update,
+                              dc->writeback_rate_update_seconds * HZ);
+}
+
+void bch_writeback_exit(void)
+{
+        if (dirty_wq)
+                destroy_workqueue(dirty_wq);
+}
+
+int __init bch_writeback_init(void)
+{
+        dirty_wq = create_singlethread_workqueue("bcache_writeback");
+        if (!dirty_wq)
+                return -ENOMEM;
+
+        return 0;
+}