5 files changed, 499 insertions, 404 deletions

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index d949b781f6f8..91a02eeeb319 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -216,6 +216,13 @@ config DM_BUFIO
          as a cache, holding recently-read blocks in memory and performing
          delayed writes.
 
+config DM_BIO_PRISON
+       tristate
+       depends on BLK_DEV_DM && EXPERIMENTAL
+       ---help---
+         Some bio locking schemes used by other device-mapper targets
+         including thin provisioning.
+
 source "drivers/md/persistent-data/Kconfig"
 
 config DM_CRYPT
@@ -247,6 +254,7 @@ config DM_THIN_PROVISIONING
        tristate "Thin provisioning target (EXPERIMENTAL)"
        depends on BLK_DEV_DM && EXPERIMENTAL
        select DM_PERSISTENT_DATA
+       select DM_BIO_PRISON
        ---help---
          Provides thin provisioning and snapshots that share a data store.
 
diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index 8b2e0dffe82e..94dce8b49324 100644
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -29,6 +29,7 @@ obj-$(CONFIG_MD_FAULTY)		+= faulty.o
 obj-$(CONFIG_BLK_DEV_MD)        += md-mod.o
 obj-$(CONFIG_BLK_DEV_DM)        += dm-mod.o
 obj-$(CONFIG_DM_BUFIO)          += dm-bufio.o
+obj-$(CONFIG_DM_BIO_PRISON)     += dm-bio-prison.o
 obj-$(CONFIG_DM_CRYPT)          += dm-crypt.o
 obj-$(CONFIG_DM_DELAY)          += dm-delay.o
 obj-$(CONFIG_DM_FLAKEY)         += dm-flakey.o
diff --git a/drivers/md/dm-bio-prison.c b/drivers/md/dm-bio-prison.c
new file mode 100644
index 000000000000..e4e841567459
--- /dev/null
+++ b/drivers/md/dm-bio-prison.c
@@ -0,0 +1,415 @@
+/*
+ * Copyright (C) 2012 Red Hat, Inc.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm.h"
+#include "dm-bio-prison.h"
+
+#include <linux/spinlock.h>
+#include <linux/mempool.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+/*----------------------------------------------------------------*/
+
+struct dm_bio_prison_cell {
+        struct hlist_node list;
+        struct dm_bio_prison *prison;
+        struct dm_cell_key key;
+        struct bio *holder;
+        struct bio_list bios;
+};
+
+struct dm_bio_prison {
+        spinlock_t lock;
+        mempool_t *cell_pool;
+
+        unsigned nr_buckets;
+        unsigned hash_mask;
+        struct hlist_head *cells;
+};
+
+/*----------------------------------------------------------------*/
+
+static uint32_t calc_nr_buckets(unsigned nr_cells)
+{
+        uint32_t n = 128;
+
+        nr_cells /= 4;
+        nr_cells = min(nr_cells, 8192u);
+
+        while (n < nr_cells)
+                n <<= 1;
+
+        return n;
+}
+
+static struct kmem_cache *_cell_cache;
+
+/*
+ * @nr_cells should be the number of cells you want in use _concurrently_.
+ * Don't confuse it with the number of distinct keys.
+ */
+struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells)
+{
+        unsigned i;
+        uint32_t nr_buckets = calc_nr_buckets(nr_cells);
+        size_t len = sizeof(struct dm_bio_prison) +
+                (sizeof(struct hlist_head) * nr_buckets);
+        struct dm_bio_prison *prison = kmalloc(len, GFP_KERNEL);
+
+        if (!prison)
+                return NULL;
+
+        spin_lock_init(&prison->lock);
+        prison->cell_pool = mempool_create_slab_pool(nr_cells, _cell_cache);
+        if (!prison->cell_pool) {
+                kfree(prison);
+                return NULL;
+        }
+
+        prison->nr_buckets = nr_buckets;
+        prison->hash_mask = nr_buckets - 1;
+        prison->cells = (struct hlist_head *) (prison + 1);
+        for (i = 0; i < nr_buckets; i++)
+                INIT_HLIST_HEAD(prison->cells + i);
+
+        return prison;
+}
+EXPORT_SYMBOL_GPL(dm_bio_prison_create);
+
+void dm_bio_prison_destroy(struct dm_bio_prison *prison)
+{
+        mempool_destroy(prison->cell_pool);
+        kfree(prison);
+}
+EXPORT_SYMBOL_GPL(dm_bio_prison_destroy);
+
+static uint32_t hash_key(struct dm_bio_prison *prison, struct dm_cell_key *key)
+{
+        const unsigned long BIG_PRIME = 4294967291UL;
+        uint64_t hash = key->block * BIG_PRIME;
+
+        return (uint32_t) (hash & prison->hash_mask);
+}
+
+static int keys_equal(struct dm_cell_key *lhs, struct dm_cell_key *rhs)
+{
+               return (lhs->virtual == rhs->virtual) &&
+                       (lhs->dev == rhs->dev) &&
+                       (lhs->block == rhs->block);
+}
+
+static struct dm_bio_prison_cell *__search_bucket(struct hlist_head *bucket,
+                                                  struct dm_cell_key *key)
+{
+        struct dm_bio_prison_cell *cell;
+        struct hlist_node *tmp;
+
+        hlist_for_each_entry(cell, tmp, bucket, list)
+                if (keys_equal(&cell->key, key))
+                        return cell;
+
+        return NULL;
+}
+
+/*
+ * This may block if a new cell needs allocating.  You must ensure that
+ * cells will be unlocked even if the calling thread is blocked.
+ *
+ * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
+ */
+int dm_bio_detain(struct dm_bio_prison *prison, struct dm_cell_key *key,
+                  struct bio *inmate, struct dm_bio_prison_cell **ref)
+{
+        int r = 1;
+        unsigned long flags;
+        uint32_t hash = hash_key(prison, key);
+        struct dm_bio_prison_cell *cell, *cell2;
+
+        BUG_ON(hash > prison->nr_buckets);
+
+        spin_lock_irqsave(&prison->lock, flags);
+
+        cell = __search_bucket(prison->cells + hash, key);
+        if (cell) {
+                bio_list_add(&cell->bios, inmate);
+                goto out;
+        }
+
+        /*
+         * Allocate a new cell
+         */
+        spin_unlock_irqrestore(&prison->lock, flags);
+        cell2 = mempool_alloc(prison->cell_pool, GFP_NOIO);
+        spin_lock_irqsave(&prison->lock, flags);
+
+        /*
+         * We've been unlocked, so we have to double check that
+         * nobody else has inserted this cell in the meantime.
+         */
+        cell = __search_bucket(prison->cells + hash, key);
+        if (cell) {
+                mempool_free(cell2, prison->cell_pool);
+                bio_list_add(&cell->bios, inmate);
+                goto out;
+        }
+
+        /*
+         * Use new cell.
+         */
+        cell = cell2;
+
+        cell->prison = prison;
+        memcpy(&cell->key, key, sizeof(cell->key));
+        cell->holder = inmate;
+        bio_list_init(&cell->bios);
+        hlist_add_head(&cell->list, prison->cells + hash);
+
+        r = 0;
+
+out:
+        spin_unlock_irqrestore(&prison->lock, flags);
+
+        *ref = cell;
+
+        return r;
+}
+EXPORT_SYMBOL_GPL(dm_bio_detain);
+
+/*
+ * @inmates must have been initialised prior to this call
+ */
+static void __cell_release(struct dm_bio_prison_cell *cell, struct bio_list *inmates)
+{
+        struct dm_bio_prison *prison = cell->prison;
+
+        hlist_del(&cell->list);
+
+        if (inmates) {
+                bio_list_add(inmates, cell->holder);
+                bio_list_merge(inmates, &cell->bios);
+        }
+
+        mempool_free(cell, prison->cell_pool);
+}
+
+void dm_cell_release(struct dm_bio_prison_cell *cell, struct bio_list *bios)
+{
+        unsigned long flags;
+        struct dm_bio_prison *prison = cell->prison;
+
+        spin_lock_irqsave(&prison->lock, flags);
+        __cell_release(cell, bios);
+        spin_unlock_irqrestore(&prison->lock, flags);
+}
+EXPORT_SYMBOL_GPL(dm_cell_release);
+
+/*
+ * There are a couple of places where we put a bio into a cell briefly
+ * before taking it out again.  In these situations we know that no other
+ * bio may be in the cell.  This function releases the cell, and also does
+ * a sanity check.
+ */
+static void __cell_release_singleton(struct dm_bio_prison_cell *cell, struct bio *bio)
+{
+        BUG_ON(cell->holder != bio);
+        BUG_ON(!bio_list_empty(&cell->bios));
+
+        __cell_release(cell, NULL);
+}
+
+void dm_cell_release_singleton(struct dm_bio_prison_cell *cell, struct bio *bio)
+{
+        unsigned long flags;
+        struct dm_bio_prison *prison = cell->prison;
+
+        spin_lock_irqsave(&prison->lock, flags);
+        __cell_release_singleton(cell, bio);
+        spin_unlock_irqrestore(&prison->lock, flags);
+}
+EXPORT_SYMBOL_GPL(dm_cell_release_singleton);
+
+/*
+ * Sometimes we don't want the holder, just the additional bios.
+ */
+static void __cell_release_no_holder(struct dm_bio_prison_cell *cell, struct bio_list *inmates)
+{
+        struct dm_bio_prison *prison = cell->prison;
+
+        hlist_del(&cell->list);
+        bio_list_merge(inmates, &cell->bios);
+
+        mempool_free(cell, prison->cell_pool);
+}
+
+void dm_cell_release_no_holder(struct dm_bio_prison_cell *cell, struct bio_list *inmates)
+{
+        unsigned long flags;
+        struct dm_bio_prison *prison = cell->prison;
+
+        spin_lock_irqsave(&prison->lock, flags);
+        __cell_release_no_holder(cell, inmates);
+        spin_unlock_irqrestore(&prison->lock, flags);
+}
+EXPORT_SYMBOL_GPL(dm_cell_release_no_holder);
+
+void dm_cell_error(struct dm_bio_prison_cell *cell)
+{
+        struct dm_bio_prison *prison = cell->prison;
+        struct bio_list bios;
+        struct bio *bio;
+        unsigned long flags;
+
+        bio_list_init(&bios);
+
+        spin_lock_irqsave(&prison->lock, flags);
+        __cell_release(cell, &bios);
+        spin_unlock_irqrestore(&prison->lock, flags);
+
+        while ((bio = bio_list_pop(&bios)))
+                bio_io_error(bio);
+}
+EXPORT_SYMBOL_GPL(dm_cell_error);
+
+/*----------------------------------------------------------------*/
+
+#define DEFERRED_SET_SIZE 64
+
+struct dm_deferred_entry {
+        struct dm_deferred_set *ds;
+        unsigned count;
+        struct list_head work_items;
+};
+
+struct dm_deferred_set {
+        spinlock_t lock;
+        unsigned current_entry;
+        unsigned sweeper;
+        struct dm_deferred_entry entries[DEFERRED_SET_SIZE];
+};
+
+struct dm_deferred_set *dm_deferred_set_create(void)
+{
+        int i;
+        struct dm_deferred_set *ds;
+
+        ds = kmalloc(sizeof(*ds), GFP_KERNEL);
+        if (!ds)
+                return NULL;
+
+        spin_lock_init(&ds->lock);
+        ds->current_entry = 0;
+        ds->sweeper = 0;
+        for (i = 0; i < DEFERRED_SET_SIZE; i++) {
+                ds->entries[i].ds = ds;
+                ds->entries[i].count = 0;
+                INIT_LIST_HEAD(&ds->entries[i].work_items);
+        }
+
+        return ds;
+}
+EXPORT_SYMBOL_GPL(dm_deferred_set_create);
+
+void dm_deferred_set_destroy(struct dm_deferred_set *ds)
+{
+        kfree(ds);
+}
+EXPORT_SYMBOL_GPL(dm_deferred_set_destroy);
+
+struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds)
+{
+        unsigned long flags;
+        struct dm_deferred_entry *entry;
+
+        spin_lock_irqsave(&ds->lock, flags);
+        entry = ds->entries + ds->current_entry;
+        entry->count++;
+        spin_unlock_irqrestore(&ds->lock, flags);
+
+        return entry;
+}
+EXPORT_SYMBOL_GPL(dm_deferred_entry_inc);
+
+static unsigned ds_next(unsigned index)
+{
+        return (index + 1) % DEFERRED_SET_SIZE;
+}
+
+static void __sweep(struct dm_deferred_set *ds, struct list_head *head)
+{
+        while ((ds->sweeper != ds->current_entry) &&
+               !ds->entries[ds->sweeper].count) {
+                list_splice_init(&ds->entries[ds->sweeper].work_items, head);
+                ds->sweeper = ds_next(ds->sweeper);
+        }
+
+        if ((ds->sweeper == ds->current_entry) && !ds->entries[ds->sweeper].count)
+                list_splice_init(&ds->entries[ds->sweeper].work_items, head);
+}
+
+void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&entry->ds->lock, flags);
+        BUG_ON(!entry->count);
+        --entry->count;
+        __sweep(entry->ds, head);
+        spin_unlock_irqrestore(&entry->ds->lock, flags);
+}
+EXPORT_SYMBOL_GPL(dm_deferred_entry_dec);
+
+/*
+ * Returns 1 if deferred or 0 if no pending items to delay job.
+ */
+int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work)
+{
+        int r = 1;
+        unsigned long flags;
+        unsigned next_entry;
+
+        spin_lock_irqsave(&ds->lock, flags);
+        if ((ds->sweeper == ds->current_entry) &&
+            !ds->entries[ds->current_entry].count)
+                r = 0;
+        else {
+                list_add(work, &ds->entries[ds->current_entry].work_items);
+                next_entry = ds_next(ds->current_entry);
+                if (!ds->entries[next_entry].count)
+                        ds->current_entry = next_entry;
+        }
+        spin_unlock_irqrestore(&ds->lock, flags);
+
+        return r;
+}
+EXPORT_SYMBOL_GPL(dm_deferred_set_add_work);
+
+/*----------------------------------------------------------------*/
+
+static int __init dm_bio_prison_init(void)
+{
+        _cell_cache = KMEM_CACHE(dm_bio_prison_cell, 0);
+        if (!_cell_cache)
+                return -ENOMEM;
+
+        return 0;
+}
+
+static void __exit dm_bio_prison_exit(void)
+{
+        kmem_cache_destroy(_cell_cache);
+        _cell_cache = NULL;
+}
+
+/*
+ * module hooks
+ */
+module_init(dm_bio_prison_init);
+module_exit(dm_bio_prison_exit);
+
+MODULE_DESCRIPTION(DM_NAME " bio prison");
+MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
+MODULE_LICENSE("GPL");
diff --git a/drivers/md/dm-bio-prison.h b/drivers/md/dm-bio-prison.h
new file mode 100644
index 000000000000..4e0ac376700a
--- /dev/null
+++ b/drivers/md/dm-bio-prison.h
@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2011-2012 Red Hat, Inc.
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef DM_BIO_PRISON_H
+#define DM_BIO_PRISON_H
+
+#include "persistent-data/dm-block-manager.h" /* FIXME: for dm_block_t */
+#include "dm-thin-metadata.h" /* FIXME: for dm_thin_id */
+
+#include <linux/list.h>
+#include <linux/bio.h>
+
+/*----------------------------------------------------------------*/
+
+/*
+ * Sometimes we can't deal with a bio straight away.  We put them in prison
+ * where they can't cause any mischief.  Bios are put in a cell identified
+ * by a key, multiple bios can be in the same cell.  When the cell is
+ * subsequently unlocked the bios become available.
+ */
+struct dm_bio_prison;
+struct dm_bio_prison_cell;
+
+/* FIXME: this needs to be more abstract */
+struct dm_cell_key {
+        int virtual;
+        dm_thin_id dev;
+        dm_block_t block;
+};
+
+struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells);
+void dm_bio_prison_destroy(struct dm_bio_prison *prison);
+
+/*
+ * This may block if a new cell needs allocating.  You must ensure that
+ * cells will be unlocked even if the calling thread is blocked.
+ *
+ * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
+ */
+int dm_bio_detain(struct dm_bio_prison *prison, struct dm_cell_key *key,
+                  struct bio *inmate, struct dm_bio_prison_cell **ref);
+
+void dm_cell_release(struct dm_bio_prison_cell *cell, struct bio_list *bios);
+void dm_cell_release_singleton(struct dm_bio_prison_cell *cell, struct bio *bio); // FIXME: bio arg not needed
+void dm_cell_release_no_holder(struct dm_bio_prison_cell *cell, struct bio_list *inmates);
+void dm_cell_error(struct dm_bio_prison_cell *cell);
+
+/*----------------------------------------------------------------*/
+
+/*
+ * We use the deferred set to keep track of pending reads to shared blocks.
+ * We do this to ensure the new mapping caused by a write isn't performed
+ * until these prior reads have completed.  Otherwise the insertion of the
+ * new mapping could free the old block that the read bios are mapped to.
+ */
+
+struct dm_deferred_set;
+struct dm_deferred_entry;
+
+struct dm_deferred_set *dm_deferred_set_create(void);
+void dm_deferred_set_destroy(struct dm_deferred_set *ds);
+
+struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds);
+void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head);
+int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work);
+
+/*----------------------------------------------------------------*/
+
+#endif
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 22a22a701e16..058acf3a5ba7 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -5,6 +5,7 @@
  */
 
 #include "dm-thin-metadata.h"
+#include "dm-bio-prison.h"
 #include "dm.h"
 
 #include <linux/device-mapper.h>
@@ -21,7 +22,6 @@
  * Tunable constants
  */
 #define ENDIO_HOOK_POOL_SIZE 1024
-#define DEFERRED_SET_SIZE 64
 #define MAPPING_POOL_SIZE 1024
 #define PRISON_CELLS 1024
 #define COMMIT_PERIOD HZ
@@ -99,404 +99,6 @@
 /*----------------------------------------------------------------*/
 
 /*
- * Sometimes we can't deal with a bio straight away.  We put them in prison
- * where they can't cause any mischief.  Bios are put in a cell identified
- * by a key, multiple bios can be in the same cell.  When the cell is
- * subsequently unlocked the bios become available.
- */
-struct dm_bio_prison;
-
-struct dm_cell_key {
-        int virtual;
-        dm_thin_id dev;
-        dm_block_t block;
-};
-
-struct dm_bio_prison_cell {
-        struct hlist_node list;
-        struct dm_bio_prison *prison;
-        struct dm_cell_key key;
-        struct bio *holder;
-        struct bio_list bios;
-};
-
-struct dm_bio_prison {
-        spinlock_t lock;
-        mempool_t *cell_pool;
-
-        unsigned nr_buckets;
-        unsigned hash_mask;
-        struct hlist_head *cells;
-};
-
-static uint32_t calc_nr_buckets(unsigned nr_cells)
-{
-        uint32_t n = 128;
-
-        nr_cells /= 4;
-        nr_cells = min(nr_cells, 8192u);
-
-        while (n < nr_cells)
-                n <<= 1;
-
-        return n;
-}
-
-static struct kmem_cache *_cell_cache;
-
-/*
- * @nr_cells should be the number of cells you want in use _concurrently_.
- * Don't confuse it with the number of distinct keys.
- */
-static struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells)
-{
-        unsigned i;
-        uint32_t nr_buckets = calc_nr_buckets(nr_cells);
-        size_t len = sizeof(struct dm_bio_prison) +
-                (sizeof(struct hlist_head) * nr_buckets);
-        struct dm_bio_prison *prison = kmalloc(len, GFP_KERNEL);
-
-        if (!prison)
-                return NULL;
-
-        spin_lock_init(&prison->lock);
-        prison->cell_pool = mempool_create_slab_pool(nr_cells, _cell_cache);
-        if (!prison->cell_pool) {
-                kfree(prison);
-                return NULL;
-        }
-
-        prison->nr_buckets = nr_buckets;
-        prison->hash_mask = nr_buckets - 1;
-        prison->cells = (struct hlist_head *) (prison + 1);
-        for (i = 0; i < nr_buckets; i++)
-                INIT_HLIST_HEAD(prison->cells + i);
-
-        return prison;
-}
-
-static void dm_bio_prison_destroy(struct dm_bio_prison *prison)
-{
-        mempool_destroy(prison->cell_pool);
-        kfree(prison);
-}
-
-static uint32_t hash_key(struct dm_bio_prison *prison, struct dm_cell_key *key)
-{
-        const unsigned long BIG_PRIME = 4294967291UL;
-        uint64_t hash = key->block * BIG_PRIME;
-
-        return (uint32_t) (hash & prison->hash_mask);
-}
-
-static int keys_equal(struct dm_cell_key *lhs, struct dm_cell_key *rhs)
-{
-               return (lhs->virtual == rhs->virtual) &&
-                       (lhs->dev == rhs->dev) &&
-                       (lhs->block == rhs->block);
-}
-
-static struct dm_bio_prison_cell *__search_bucket(struct hlist_head *bucket,
-                                                  struct dm_cell_key *key)
-{
-        struct dm_bio_prison_cell *cell;
-        struct hlist_node *tmp;
-
-        hlist_for_each_entry(cell, tmp, bucket, list)
-                if (keys_equal(&cell->key, key))
-                        return cell;
-
-        return NULL;
-}
-
-/*
- * This may block if a new cell needs allocating.  You must ensure that
- * cells will be unlocked even if the calling thread is blocked.
- *
- * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
- */
-static int dm_bio_detain(struct dm_bio_prison *prison, struct dm_cell_key *key,
-                         struct bio *inmate, struct dm_bio_prison_cell **ref)
-{
-        int r = 1;
-        unsigned long flags;
-        uint32_t hash = hash_key(prison, key);
-        struct dm_bio_prison_cell *cell, *cell2;
-
-        BUG_ON(hash > prison->nr_buckets);
-
-        spin_lock_irqsave(&prison->lock, flags);
-
-        cell = __search_bucket(prison->cells + hash, key);
-        if (cell) {
-                bio_list_add(&cell->bios, inmate);
-                goto out;
-        }
-
-        /*
-         * Allocate a new cell
-         */
-        spin_unlock_irqrestore(&prison->lock, flags);
-        cell2 = mempool_alloc(prison->cell_pool, GFP_NOIO);
-        spin_lock_irqsave(&prison->lock, flags);
-
-        /*
-         * We've been unlocked, so we have to double check that
-         * nobody else has inserted this cell in the meantime.
-         */
-        cell = __search_bucket(prison->cells + hash, key);
-        if (cell) {
-                mempool_free(cell2, prison->cell_pool);
-                bio_list_add(&cell->bios, inmate);
-                goto out;
-        }
-
-        /*
-         * Use new cell.
-         */
-        cell = cell2;
-
-        cell->prison = prison;
-        memcpy(&cell->key, key, sizeof(cell->key));
-        cell->holder = inmate;
-        bio_list_init(&cell->bios);
-        hlist_add_head(&cell->list, prison->cells + hash);
-
-        r = 0;
-
-out:
-        spin_unlock_irqrestore(&prison->lock, flags);
-
-        *ref = cell;
-
-        return r;
-}
-
-/*
- * @inmates must have been initialised prior to this call
- */
-static void __cell_release(struct dm_bio_prison_cell *cell, struct bio_list *inmates)
-{
-        struct dm_bio_prison *prison = cell->prison;
-
-        hlist_del(&cell->list);
-
-        if (inmates) {
-                bio_list_add(inmates, cell->holder);
-                bio_list_merge(inmates, &cell->bios);
-        }
-
-        mempool_free(cell, prison->cell_pool);
-}
-
-static void dm_cell_release(struct dm_bio_prison_cell *cell, struct bio_list *bios)
-{
-        unsigned long flags;
-        struct dm_bio_prison *prison = cell->prison;
-
-        spin_lock_irqsave(&prison->lock, flags);
-        __cell_release(cell, bios);
-        spin_unlock_irqrestore(&prison->lock, flags);
-}
-
-/*
- * There are a couple of places where we put a bio into a cell briefly
- * before taking it out again.  In these situations we know that no other
- * bio may be in the cell.  This function releases the cell, and also does
- * a sanity check.
- */
-static void __cell_release_singleton(struct dm_bio_prison_cell *cell, struct bio *bio)
-{
-        BUG_ON(cell->holder != bio);
-        BUG_ON(!bio_list_empty(&cell->bios));
-
-        __cell_release(cell, NULL);
-}
-
-static void dm_cell_release_singleton(struct dm_bio_prison_cell *cell, struct bio *bio)
-{
-        unsigned long flags;
-        struct dm_bio_prison *prison = cell->prison;
-
-        spin_lock_irqsave(&prison->lock, flags);
-        __cell_release_singleton(cell, bio);
-        spin_unlock_irqrestore(&prison->lock, flags);
-}
-
-/*
- * Sometimes we don't want the holder, just the additional bios.
- */
-static void __cell_release_no_holder(struct dm_bio_prison_cell *cell,
-                                     struct bio_list *inmates)
-{
-        struct dm_bio_prison *prison = cell->prison;
-
-        hlist_del(&cell->list);
-        bio_list_merge(inmates, &cell->bios);
-
-        mempool_free(cell, prison->cell_pool);
-}
-
-static void dm_cell_release_no_holder(struct dm_bio_prison_cell *cell,
-                                      struct bio_list *inmates)
-{
-        unsigned long flags;
-        struct dm_bio_prison *prison = cell->prison;
-
-        spin_lock_irqsave(&prison->lock, flags);
-        __cell_release_no_holder(cell, inmates);
-        spin_unlock_irqrestore(&prison->lock, flags);
-}
-
-static void dm_cell_error(struct dm_bio_prison_cell *cell)
-{
-        struct dm_bio_prison *prison = cell->prison;
-        struct bio_list bios;
-        struct bio *bio;
-        unsigned long flags;
-
-        bio_list_init(&bios);
-
-        spin_lock_irqsave(&prison->lock, flags);
-        __cell_release(cell, &bios);
-        spin_unlock_irqrestore(&prison->lock, flags);
-
-        while ((bio = bio_list_pop(&bios)))
-                bio_io_error(bio);
-}
-
-/*----------------------------------------------------------------*/
-
-/*
- * We use the deferred set to keep track of pending reads to shared blocks.
- * We do this to ensure the new mapping caused by a write isn't performed
- * until these prior reads have completed.  Otherwise the insertion of the
- * new mapping could free the old block that the read bios are mapped to.
- */
-
-struct dm_deferred_set;
-struct dm_deferred_entry {
-        struct dm_deferred_set *ds;
-        unsigned count;
-        struct list_head work_items;
-};
-
-struct dm_deferred_set {
-        spinlock_t lock;
-        unsigned current_entry;
-        unsigned sweeper;
-        struct dm_deferred_entry entries[DEFERRED_SET_SIZE];
-};
-
-static struct dm_deferred_set *dm_deferred_set_create(void)
-{
-        int i;
-        struct dm_deferred_set *ds;
-
-        ds = kmalloc(sizeof(*ds), GFP_KERNEL);
-        if (!ds)
-                return NULL;
-
-        spin_lock_init(&ds->lock);
-        ds->current_entry = 0;
-        ds->sweeper = 0;
-        for (i = 0; i < DEFERRED_SET_SIZE; i++) {
-                ds->entries[i].ds = ds;
-                ds->entries[i].count = 0;
-                INIT_LIST_HEAD(&ds->entries[i].work_items);
-        }
-
-        return ds;
-}
-
-static void dm_deferred_set_destroy(struct dm_deferred_set *ds)
-{
-        kfree(ds);
-}
-
-static struct dm_deferred_entry *dm_deferred_entry_inc(struct dm_deferred_set *ds)
-{
-        unsigned long flags;
-        struct dm_deferred_entry *entry;
-
-        spin_lock_irqsave(&ds->lock, flags);
-        entry = ds->entries + ds->current_entry;
-        entry->count++;
-        spin_unlock_irqrestore(&ds->lock, flags);
-
-        return entry;
-}
-
-static unsigned ds_next(unsigned index)
-{
-        return (index + 1) % DEFERRED_SET_SIZE;
-}
-
-static void __sweep(struct dm_deferred_set *ds, struct list_head *head)
-{
-        while ((ds->sweeper != ds->current_entry) &&
-               !ds->entries[ds->sweeper].count) {
-                list_splice_init(&ds->entries[ds->sweeper].work_items, head);
-                ds->sweeper = ds_next(ds->sweeper);
-        }
-
-        if ((ds->sweeper == ds->current_entry) && !ds->entries[ds->sweeper].count)
-                list_splice_init(&ds->entries[ds->sweeper].work_items, head);
-}
-
-static void dm_deferred_entry_dec(struct dm_deferred_entry *entry, struct list_head *head)
-{
-        unsigned long flags;
-
-        spin_lock_irqsave(&entry->ds->lock, flags);
-        BUG_ON(!entry->count);
-        --entry->count;
-        __sweep(entry->ds, head);
-        spin_unlock_irqrestore(&entry->ds->lock, flags);
-}
-
-/*
- * Returns 1 if deferred or 0 if no pending items to delay job.
- */
-static int dm_deferred_set_add_work(struct dm_deferred_set *ds, struct list_head *work)
-{
-        int r = 1;
-        unsigned long flags;
-        unsigned next_entry;
-
-        spin_lock_irqsave(&ds->lock, flags);
-        if ((ds->sweeper == ds->current_entry) &&
-            !ds->entries[ds->current_entry].count)
-                r = 0;
-        else {
-                list_add(work, &ds->entries[ds->current_entry].work_items);
-                next_entry = ds_next(ds->current_entry);
-                if (!ds->entries[next_entry].count)
-                        ds->current_entry = next_entry;
-        }
-        spin_unlock_irqrestore(&ds->lock, flags);
-
-        return r;
-}
-
-static int __init dm_bio_prison_init(void)
-{
-        _cell_cache = KMEM_CACHE(dm_bio_prison_cell, 0);
-        if (!_cell_cache)
-                return -ENOMEM;
-
-        return 0;
-}
-
-static void __exit dm_bio_prison_exit(void)
-{
-        kmem_cache_destroy(_cell_cache);
-        _cell_cache = NULL;
-}
-
-/*----------------------------------------------------------------*/
-
-/*
  * Key building.
  */
 static void build_data_key(struct dm_thin_device *td,
@@ -2852,7 +2454,7 @@ static struct target_type pool_target = {
         .name = "thin-pool",
         .features = DM_TARGET_SINGLETON | DM_TARGET_ALWAYS_WRITEABLE |
                     DM_TARGET_IMMUTABLE,
-        .version = {1, 4, 0},
+        .version = {1, 5, 0},
         .module = THIS_MODULE,
         .ctr = pool_ctr,
         .dtr = pool_dtr,
@@ -3143,7 +2745,7 @@ static void thin_io_hints(struct dm_target *ti, struct queue_limits *limits)
 
 static struct target_type thin_target = {
         .name = "thin",
-        .version = {1, 4, 0},
+        .version = {1, 5, 0},
         .module = THIS_MODULE,
         .ctr = thin_ctr,
         .dtr = thin_dtr,
@@ -3173,8 +2775,6 @@ static int __init dm_thin_init(void)
 
         r = -ENOMEM;
 
-        dm_bio_prison_init();
-
         _new_mapping_cache = KMEM_CACHE(dm_thin_new_mapping, 0);
         if (!_new_mapping_cache)
                 goto bad_new_mapping_cache;
@@ -3200,7 +2800,6 @@ static void dm_thin_exit(void)
         dm_unregister_target(&thin_target);
         dm_unregister_target(&pool_target);
 
-        dm_bio_prison_exit();
         kmem_cache_destroy(_new_mapping_cache);
         kmem_cache_destroy(_endio_hook_cache);
 }