1 files changed, 1269 insertions, 0 deletions

diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
new file mode 100644
index 000000000000..6e3cf7e13451
--- /dev/null
+++ b/drivers/md/dm-raid1.c
@@ -0,0 +1,1269 @@
+/*
+ * Copyright (C) 2003 Sistina Software Limited.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm.h"
+#include "dm-bio-list.h"
+#include "dm-io.h"
+#include "dm-log.h"
+#include "kcopyd.h"
+
+#include <linux/ctype.h>
+#include <linux/init.h>
+#include <linux/mempool.h>
+#include <linux/module.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/time.h>
+#include <linux/vmalloc.h>
+#include <linux/workqueue.h>
+
+static struct workqueue_struct *_kmirrord_wq;
+static struct work_struct _kmirrord_work;
+
+static inline void wake(void)
+{
+        queue_work(_kmirrord_wq, &_kmirrord_work);
+}
+
+/*-----------------------------------------------------------------
+ * Region hash
+ *
+ * The mirror splits itself up into discrete regions.  Each
+ * region can be in one of three states: clean, dirty,
+ * nosync.  There is no need to put clean regions in the hash.
+ *
+ * In addition to being present in the hash table a region _may_
+ * be present on one of three lists.
+ *
+ *   clean_regions: Regions on this list have no io pending to
+ *   them, they are in sync, we are no longer interested in them,
+ *   they are dull.  rh_update_states() will remove them from the
+ *   hash table.
+ *
+ *   quiesced_regions: These regions have been spun down, ready
+ *   for recovery.  rh_recovery_start() will remove regions from
+ *   this list and hand them to kmirrord, which will schedule the
+ *   recovery io with kcopyd.
+ *
+ *   recovered_regions: Regions that kcopyd has successfully
+ *   recovered.  rh_update_states() will now schedule any delayed
+ *   io, up the recovery_count, and remove the region from the
+ *   hash.
+ *
+ * There are 2 locks:
+ *   A rw spin lock 'hash_lock' protects just the hash table,
+ *   this is never held in write mode from interrupt context,
+ *   which I believe means that we only have to disable irqs when
+ *   doing a write lock.
+ *
+ *   An ordinary spin lock 'region_lock' that protects the three
+ *   lists in the region_hash, with the 'state', 'list' and
+ *   'bhs_delayed' fields of the regions.  This is used from irq
+ *   context, so all other uses will have to suspend local irqs.
+ *---------------------------------------------------------------*/
+struct mirror_set;
+struct region_hash {
+        struct mirror_set *ms;
+        uint32_t region_size;
+        unsigned region_shift;
+
+        /* holds persistent region state */
+        struct dirty_log *log;
+
+        /* hash table */
+        rwlock_t hash_lock;
+        mempool_t *region_pool;
+        unsigned int mask;
+        unsigned int nr_buckets;
+        struct list_head *buckets;
+
+        spinlock_t region_lock;
+        struct semaphore recovery_count;
+        struct list_head clean_regions;
+        struct list_head quiesced_regions;
+        struct list_head recovered_regions;
+};
+
+enum {
+        RH_CLEAN,
+        RH_DIRTY,
+        RH_NOSYNC,
+        RH_RECOVERING
+};
+
+struct region {
+        struct region_hash *rh; /* FIXME: can we get rid of this ? */
+        region_t key;
+        int state;
+
+        struct list_head hash_list;
+        struct list_head list;
+
+        atomic_t pending;
+        struct bio_list delayed_bios;
+};
+
+/*
+ * Conversion fns
+ */
+static inline region_t bio_to_region(struct region_hash *rh, struct bio *bio)
+{
+        return bio->bi_sector >> rh->region_shift;
+}
+
+static inline sector_t region_to_sector(struct region_hash *rh, region_t region)
+{
+        return region << rh->region_shift;
+}
+
+/* FIXME move this */
+static void queue_bio(struct mirror_set *ms, struct bio *bio, int rw);
+
+static void *region_alloc(unsigned int __nocast gfp_mask, void *pool_data)
+{
+        return kmalloc(sizeof(struct region), gfp_mask);
+}
+
+static void region_free(void *element, void *pool_data)
+{
+        kfree(element);
+}
+
+#define MIN_REGIONS 64
+#define MAX_RECOVERY 1
+static int rh_init(struct region_hash *rh, struct mirror_set *ms,
+                   struct dirty_log *log, uint32_t region_size,
+                   region_t nr_regions)
+{
+        unsigned int nr_buckets, max_buckets;
+        size_t i;
+
+        /*
+         * Calculate a suitable number of buckets for our hash
+         * table.
+         */
+        max_buckets = nr_regions >> 6;
+        for (nr_buckets = 128u; nr_buckets < max_buckets; nr_buckets <<= 1)
+                ;
+        nr_buckets >>= 1;
+
+        rh->ms = ms;
+        rh->log = log;
+        rh->region_size = region_size;
+        rh->region_shift = ffs(region_size) - 1;
+        rwlock_init(&rh->hash_lock);
+        rh->mask = nr_buckets - 1;
+        rh->nr_buckets = nr_buckets;
+
+        rh->buckets = vmalloc(nr_buckets * sizeof(*rh->buckets));
+        if (!rh->buckets) {
+                DMERR("unable to allocate region hash memory");
+                return -ENOMEM;
+        }
+
+        for (i = 0; i < nr_buckets; i++)
+                INIT_LIST_HEAD(rh->buckets + i);
+
+        spin_lock_init(&rh->region_lock);
+        sema_init(&rh->recovery_count, 0);
+        INIT_LIST_HEAD(&rh->clean_regions);
+        INIT_LIST_HEAD(&rh->quiesced_regions);
+        INIT_LIST_HEAD(&rh->recovered_regions);
+
+        rh->region_pool = mempool_create(MIN_REGIONS, region_alloc,
+                                         region_free, NULL);
+        if (!rh->region_pool) {
+                vfree(rh->buckets);
+                rh->buckets = NULL;
+                return -ENOMEM;
+        }
+
+        return 0;
+}
+
+static void rh_exit(struct region_hash *rh)
+{
+        unsigned int h;
+        struct region *reg, *nreg;
+
+        BUG_ON(!list_empty(&rh->quiesced_regions));
+        for (h = 0; h < rh->nr_buckets; h++) {
+                list_for_each_entry_safe(reg, nreg, rh->buckets + h, hash_list) {
+                        BUG_ON(atomic_read(&reg->pending));
+                        mempool_free(reg, rh->region_pool);
+                }
+        }
+
+        if (rh->log)
+                dm_destroy_dirty_log(rh->log);
+        if (rh->region_pool)
+                mempool_destroy(rh->region_pool);
+        vfree(rh->buckets);
+}
+
+#define RH_HASH_MULT 2654435387U
+
+static inline unsigned int rh_hash(struct region_hash *rh, region_t region)
+{
+        return (unsigned int) ((region * RH_HASH_MULT) >> 12) & rh->mask;
+}
+
+static struct region *__rh_lookup(struct region_hash *rh, region_t region)
+{
+        struct region *reg;
+
+        list_for_each_entry (reg, rh->buckets + rh_hash(rh, region), hash_list)
+                if (reg->key == region)
+                        return reg;
+
+        return NULL;
+}
+
+static void __rh_insert(struct region_hash *rh, struct region *reg)
+{
+        unsigned int h = rh_hash(rh, reg->key);
+        list_add(&reg->hash_list, rh->buckets + h);
+}
+
+static struct region *__rh_alloc(struct region_hash *rh, region_t region)
+{
+        struct region *reg, *nreg;
+
+        read_unlock(&rh->hash_lock);
+        nreg = mempool_alloc(rh->region_pool, GFP_NOIO);
+        nreg->state = rh->log->type->in_sync(rh->log, region, 1) ?
+                RH_CLEAN : RH_NOSYNC;
+        nreg->rh = rh;
+        nreg->key = region;
+
+        INIT_LIST_HEAD(&nreg->list);
+
+        atomic_set(&nreg->pending, 0);
+        bio_list_init(&nreg->delayed_bios);
+        write_lock_irq(&rh->hash_lock);
+
+        reg = __rh_lookup(rh, region);
+        if (reg)
+                /* we lost the race */
+                mempool_free(nreg, rh->region_pool);
+
+        else {
+                __rh_insert(rh, nreg);
+                if (nreg->state == RH_CLEAN) {
+                        spin_lock(&rh->region_lock);
+                        list_add(&nreg->list, &rh->clean_regions);
+                        spin_unlock(&rh->region_lock);
+                }
+                reg = nreg;
+        }
+        write_unlock_irq(&rh->hash_lock);
+        read_lock(&rh->hash_lock);
+
+        return reg;
+}
+
+static inline struct region *__rh_find(struct region_hash *rh, region_t region)
+{
+        struct region *reg;
+
+        reg = __rh_lookup(rh, region);
+        if (!reg)
+                reg = __rh_alloc(rh, region);
+
+        return reg;
+}
+
+static int rh_state(struct region_hash *rh, region_t region, int may_block)
+{
+        int r;
+        struct region *reg;
+
+        read_lock(&rh->hash_lock);
+        reg = __rh_lookup(rh, region);
+        read_unlock(&rh->hash_lock);
+
+        if (reg)
+                return reg->state;
+
+        /*
+         * The region wasn't in the hash, so we fall back to the
+         * dirty log.
+         */
+        r = rh->log->type->in_sync(rh->log, region, may_block);
+
+        /*
+         * Any error from the dirty log (eg. -EWOULDBLOCK) gets
+         * taken as a RH_NOSYNC
+         */
+        return r == 1 ? RH_CLEAN : RH_NOSYNC;
+}
+
+static inline int rh_in_sync(struct region_hash *rh,
+                             region_t region, int may_block)
+{
+        int state = rh_state(rh, region, may_block);
+        return state == RH_CLEAN || state == RH_DIRTY;
+}
+
+static void dispatch_bios(struct mirror_set *ms, struct bio_list *bio_list)
+{
+        struct bio *bio;
+
+        while ((bio = bio_list_pop(bio_list))) {
+                queue_bio(ms, bio, WRITE);
+        }
+}
+
+static void rh_update_states(struct region_hash *rh)
+{
+        struct region *reg, *next;
+
+        LIST_HEAD(clean);
+        LIST_HEAD(recovered);
+
+        /*
+         * Quickly grab the lists.
+         */
+        write_lock_irq(&rh->hash_lock);
+        spin_lock(&rh->region_lock);
+        if (!list_empty(&rh->clean_regions)) {
+                list_splice(&rh->clean_regions, &clean);
+                INIT_LIST_HEAD(&rh->clean_regions);
+
+                list_for_each_entry (reg, &clean, list) {
+                        rh->log->type->clear_region(rh->log, reg->key);
+                        list_del(&reg->hash_list);
+                }
+        }
+
+        if (!list_empty(&rh->recovered_regions)) {
+                list_splice(&rh->recovered_regions, &recovered);
+                INIT_LIST_HEAD(&rh->recovered_regions);
+
+                list_for_each_entry (reg, &recovered, list)
+                        list_del(&reg->hash_list);
+        }
+        spin_unlock(&rh->region_lock);
+        write_unlock_irq(&rh->hash_lock);
+
+        /*
+         * All the regions on the recovered and clean lists have
+         * now been pulled out of the system, so no need to do
+         * any more locking.
+         */
+        list_for_each_entry_safe (reg, next, &recovered, list) {
+                rh->log->type->clear_region(rh->log, reg->key);
+                rh->log->type->complete_resync_work(rh->log, reg->key, 1);
+                dispatch_bios(rh->ms, &reg->delayed_bios);
+                up(&rh->recovery_count);
+                mempool_free(reg, rh->region_pool);
+        }
+
+        if (!list_empty(&recovered))
+                rh->log->type->flush(rh->log);
+
+        list_for_each_entry_safe (reg, next, &clean, list)
+                mempool_free(reg, rh->region_pool);
+}
+
+static void rh_inc(struct region_hash *rh, region_t region)
+{
+        struct region *reg;
+
+        read_lock(&rh->hash_lock);
+        reg = __rh_find(rh, region);
+        if (reg->state == RH_CLEAN) {
+                rh->log->type->mark_region(rh->log, reg->key);
+
+                spin_lock_irq(&rh->region_lock);
+                reg->state = RH_DIRTY;
+                list_del_init(&reg->list);      /* take off the clean list */
+                spin_unlock_irq(&rh->region_lock);
+        }
+
+        atomic_inc(&reg->pending);
+        read_unlock(&rh->hash_lock);
+}
+
+static void rh_inc_pending(struct region_hash *rh, struct bio_list *bios)
+{
+        struct bio *bio;
+
+        for (bio = bios->head; bio; bio = bio->bi_next)
+                rh_inc(rh, bio_to_region(rh, bio));
+}
+
+static void rh_dec(struct region_hash *rh, region_t region)
+{
+        unsigned long flags;
+        struct region *reg;
+        int should_wake = 0;
+
+        read_lock(&rh->hash_lock);
+        reg = __rh_lookup(rh, region);
+        read_unlock(&rh->hash_lock);
+
+        if (atomic_dec_and_test(&reg->pending)) {
+                spin_lock_irqsave(&rh->region_lock, flags);
+                if (reg->state == RH_RECOVERING) {
+                        list_add_tail(&reg->list, &rh->quiesced_regions);
+                } else {
+                        reg->state = RH_CLEAN;
+                        list_add(&reg->list, &rh->clean_regions);
+                }
+                spin_unlock_irqrestore(&rh->region_lock, flags);
+                should_wake = 1;
+        }
+
+        if (should_wake)
+                wake();
+}
+
+/*
+ * Starts quiescing a region in preparation for recovery.
+ */
+static int __rh_recovery_prepare(struct region_hash *rh)
+{
+        int r;
+        struct region *reg;
+        region_t region;
+
+        /*
+         * Ask the dirty log what's next.
+         */
+        r = rh->log->type->get_resync_work(rh->log, &region);
+        if (r <= 0)
+                return r;
+
+        /*
+         * Get this region, and start it quiescing by setting the
+         * recovering flag.
+         */
+        read_lock(&rh->hash_lock);
+        reg = __rh_find(rh, region);
+        read_unlock(&rh->hash_lock);
+
+        spin_lock_irq(&rh->region_lock);
+        reg->state = RH_RECOVERING;
+
+        /* Already quiesced ? */
+        if (atomic_read(&reg->pending))
+                list_del_init(&reg->list);
+
+        else {
+                list_del_init(&reg->list);
+                list_add(&reg->list, &rh->quiesced_regions);
+        }
+        spin_unlock_irq(&rh->region_lock);
+
+        return 1;
+}
+
+static void rh_recovery_prepare(struct region_hash *rh)
+{
+        while (!down_trylock(&rh->recovery_count))
+                if (__rh_recovery_prepare(rh) <= 0) {
+                        up(&rh->recovery_count);
+                        break;
+                }
+}
+
+/*
+ * Returns any quiesced regions.
+ */
+static struct region *rh_recovery_start(struct region_hash *rh)
+{
+        struct region *reg = NULL;
+
+        spin_lock_irq(&rh->region_lock);
+        if (!list_empty(&rh->quiesced_regions)) {
+                reg = list_entry(rh->quiesced_regions.next,
+                                 struct region, list);
+                list_del_init(&reg->list);      /* remove from the quiesced list */
+        }
+        spin_unlock_irq(&rh->region_lock);
+
+        return reg;
+}
+
+/* FIXME: success ignored for now */
+static void rh_recovery_end(struct region *reg, int success)
+{
+        struct region_hash *rh = reg->rh;
+
+        spin_lock_irq(&rh->region_lock);
+        list_add(&reg->list, &reg->rh->recovered_regions);
+        spin_unlock_irq(&rh->region_lock);
+
+        wake();
+}
+
+static void rh_flush(struct region_hash *rh)
+{
+        rh->log->type->flush(rh->log);
+}
+
+static void rh_delay(struct region_hash *rh, struct bio *bio)
+{
+        struct region *reg;
+
+        read_lock(&rh->hash_lock);
+        reg = __rh_find(rh, bio_to_region(rh, bio));
+        bio_list_add(&reg->delayed_bios, bio);
+        read_unlock(&rh->hash_lock);
+}
+
+static void rh_stop_recovery(struct region_hash *rh)
+{
+        int i;
+
+        /* wait for any recovering regions */
+        for (i = 0; i < MAX_RECOVERY; i++)
+                down(&rh->recovery_count);
+}
+
+static void rh_start_recovery(struct region_hash *rh)
+{
+        int i;
+
+        for (i = 0; i < MAX_RECOVERY; i++)
+                up(&rh->recovery_count);
+
+        wake();
+}
+
+/*-----------------------------------------------------------------
+ * Mirror set structures.
+ *---------------------------------------------------------------*/
+struct mirror {
+        atomic_t error_count;
+        struct dm_dev *dev;
+        sector_t offset;
+};
+
+struct mirror_set {
+        struct dm_target *ti;
+        struct list_head list;
+        struct region_hash rh;
+        struct kcopyd_client *kcopyd_client;
+
+        spinlock_t lock;        /* protects the next two lists */
+        struct bio_list reads;
+        struct bio_list writes;
+
+        /* recovery */
+        region_t nr_regions;
+        int in_sync;
+
+        unsigned int nr_mirrors;
+        struct mirror mirror[0];
+};
+
+/*
+ * Every mirror should look like this one.
+ */
+#define DEFAULT_MIRROR 0
+
+/*
+ * This is yucky.  We squirrel the mirror_set struct away inside
+ * bi_next for write buffers.  This is safe since the bh
+ * doesn't get submitted to the lower levels of block layer.
+ */
+static struct mirror_set *bio_get_ms(struct bio *bio)
+{
+        return (struct mirror_set *) bio->bi_next;
+}
+
+static void bio_set_ms(struct bio *bio, struct mirror_set *ms)
+{
+        bio->bi_next = (struct bio *) ms;
+}
+
+/*-----------------------------------------------------------------
+ * Recovery.
+ *
+ * When a mirror is first activated we may find that some regions
+ * are in the no-sync state.  We have to recover these by
+ * recopying from the default mirror to all the others.
+ *---------------------------------------------------------------*/
+static void recovery_complete(int read_err, unsigned int write_err,
+                              void *context)
+{
+        struct region *reg = (struct region *) context;
+
+        /* FIXME: better error handling */
+        rh_recovery_end(reg, read_err || write_err);
+}
+
+static int recover(struct mirror_set *ms, struct region *reg)
+{
+        int r;
+        unsigned int i;
+        struct io_region from, to[KCOPYD_MAX_REGIONS], *dest;
+        struct mirror *m;
+        unsigned long flags = 0;
+
+        /* fill in the source */
+        m = ms->mirror + DEFAULT_MIRROR;
+        from.bdev = m->dev->bdev;
+        from.sector = m->offset + region_to_sector(reg->rh, reg->key);
+        if (reg->key == (ms->nr_regions - 1)) {
+                /*
+                 * The final region may be smaller than
+                 * region_size.
+                 */
+                from.count = ms->ti->len & (reg->rh->region_size - 1);
+                if (!from.count)
+                        from.count = reg->rh->region_size;
+        } else
+                from.count = reg->rh->region_size;
+
+        /* fill in the destinations */
+        for (i = 0, dest = to; i < ms->nr_mirrors; i++) {
+                if (i == DEFAULT_MIRROR)
+                        continue;
+
+                m = ms->mirror + i;
+                dest->bdev = m->dev->bdev;
+                dest->sector = m->offset + region_to_sector(reg->rh, reg->key);
+                dest->count = from.count;
+                dest++;
+        }
+
+        /* hand to kcopyd */
+        set_bit(KCOPYD_IGNORE_ERROR, &flags);
+        r = kcopyd_copy(ms->kcopyd_client, &from, ms->nr_mirrors - 1, to, flags,
+                        recovery_complete, reg);
+
+        return r;
+}
+
+static void do_recovery(struct mirror_set *ms)
+{
+        int r;
+        struct region *reg;
+        struct dirty_log *log = ms->rh.log;
+
+        /*
+         * Start quiescing some regions.
+         */
+        rh_recovery_prepare(&ms->rh);
+
+        /*
+         * Copy any already quiesced regions.
+         */
+        while ((reg = rh_recovery_start(&ms->rh))) {
+                r = recover(ms, reg);
+                if (r)
+                        rh_recovery_end(reg, 0);
+        }
+
+        /*
+         * Update the in sync flag.
+         */
+        if (!ms->in_sync &&
+            (log->type->get_sync_count(log) == ms->nr_regions)) {
+                /* the sync is complete */
+                dm_table_event(ms->ti->table);
+                ms->in_sync = 1;
+        }
+}
+
+/*-----------------------------------------------------------------
+ * Reads
+ *---------------------------------------------------------------*/
+static struct mirror *choose_mirror(struct mirror_set *ms, sector_t sector)
+{
+        /* FIXME: add read balancing */
+        return ms->mirror + DEFAULT_MIRROR;
+}
+
+/*
+ * remap a buffer to a particular mirror.
+ */
+static void map_bio(struct mirror_set *ms, struct mirror *m, struct bio *bio)
+{
+        bio->bi_bdev = m->dev->bdev;
+        bio->bi_sector = m->offset + (bio->bi_sector - ms->ti->begin);
+}
+
+static void do_reads(struct mirror_set *ms, struct bio_list *reads)
+{
+        region_t region;
+        struct bio *bio;
+        struct mirror *m;
+
+        while ((bio = bio_list_pop(reads))) {
+                region = bio_to_region(&ms->rh, bio);
+
+                /*
+                 * We can only read balance if the region is in sync.
+                 */
+                if (rh_in_sync(&ms->rh, region, 0))
+                        m = choose_mirror(ms, bio->bi_sector);
+                else
+                        m = ms->mirror + DEFAULT_MIRROR;
+
+                map_bio(ms, m, bio);
+                generic_make_request(bio);
+        }
+}
+
+/*-----------------------------------------------------------------
+ * Writes.
+ *
+ * We do different things with the write io depending on the
+ * state of the region that it's in:
+ *
+ * SYNC:        increment pending, use kcopyd to write to *all* mirrors
+ * RECOVERING:  delay the io until recovery completes
+ * NOSYNC:      increment pending, just write to the default mirror
+ *---------------------------------------------------------------*/
+static void write_callback(unsigned long error, void *context)
+{
+        unsigned int i;
+        int uptodate = 1;
+        struct bio *bio = (struct bio *) context;
+        struct mirror_set *ms;
+
+        ms = bio_get_ms(bio);
+        bio_set_ms(bio, NULL);
+
+        /*
+         * NOTE: We don't decrement the pending count here,
+         * instead it is done by the targets endio function.
+         * This way we handle both writes to SYNC and NOSYNC
+         * regions with the same code.
+         */
+
+        if (error) {
+                /*
+                 * only error the io if all mirrors failed.
+                 * FIXME: bogus
+                 */
+                uptodate = 0;
+                for (i = 0; i < ms->nr_mirrors; i++)
+                        if (!test_bit(i, &error)) {
+                                uptodate = 1;
+                                break;
+                        }
+        }
+        bio_endio(bio, bio->bi_size, 0);
+}
+
+static void do_write(struct mirror_set *ms, struct bio *bio)
+{
+        unsigned int i;
+        struct io_region io[KCOPYD_MAX_REGIONS+1];
+        struct mirror *m;
+
+        for (i = 0; i < ms->nr_mirrors; i++) {
+                m = ms->mirror + i;
+
+                io[i].bdev = m->dev->bdev;
+                io[i].sector = m->offset + (bio->bi_sector - ms->ti->begin);
+                io[i].count = bio->bi_size >> 9;
+        }
+
+        bio_set_ms(bio, ms);
+        dm_io_async_bvec(ms->nr_mirrors, io, WRITE,
+                         bio->bi_io_vec + bio->bi_idx,
+                         write_callback, bio);
+}
+
+static void do_writes(struct mirror_set *ms, struct bio_list *writes)
+{
+        int state;
+        struct bio *bio;
+        struct bio_list sync, nosync, recover, *this_list = NULL;
+
+        if (!writes->head)
+                return;
+
+        /*
+         * Classify each write.
+         */
+        bio_list_init(&sync);
+        bio_list_init(&nosync);
+        bio_list_init(&recover);
+
+        while ((bio = bio_list_pop(writes))) {
+                state = rh_state(&ms->rh, bio_to_region(&ms->rh, bio), 1);
+                switch (state) {
+                case RH_CLEAN:
+                case RH_DIRTY:
+                        this_list = &sync;
+                        break;
+
+                case RH_NOSYNC:
+                        this_list = &nosync;
+                        break;
+
+                case RH_RECOVERING:
+                        this_list = &recover;
+                        break;
+                }
+
+                bio_list_add(this_list, bio);
+        }
+
+        /*
+         * Increment the pending counts for any regions that will
+         * be written to (writes to recover regions are going to
+         * be delayed).
+         */
+        rh_inc_pending(&ms->rh, &sync);
+        rh_inc_pending(&ms->rh, &nosync);
+        rh_flush(&ms->rh);
+
+        /*
+         * Dispatch io.
+         */
+        while ((bio = bio_list_pop(&sync)))
+                do_write(ms, bio);
+
+        while ((bio = bio_list_pop(&recover)))
+                rh_delay(&ms->rh, bio);
+
+        while ((bio = bio_list_pop(&nosync))) {
+                map_bio(ms, ms->mirror + DEFAULT_MIRROR, bio);
+                generic_make_request(bio);
+        }
+}
+
+/*-----------------------------------------------------------------
+ * kmirrord
+ *---------------------------------------------------------------*/
+static LIST_HEAD(_mirror_sets);
+static DECLARE_RWSEM(_mirror_sets_lock);
+
+static void do_mirror(struct mirror_set *ms)
+{
+        struct bio_list reads, writes;
+
+        spin_lock(&ms->lock);
+        reads = ms->reads;
+        writes = ms->writes;
+        bio_list_init(&ms->reads);
+        bio_list_init(&ms->writes);
+        spin_unlock(&ms->lock);
+
+        rh_update_states(&ms->rh);
+        do_recovery(ms);
+        do_reads(ms, &reads);
+        do_writes(ms, &writes);
+}
+
+static void do_work(void *ignored)
+{
+        struct mirror_set *ms;
+
+        down_read(&_mirror_sets_lock);
+        list_for_each_entry (ms, &_mirror_sets, list)
+                do_mirror(ms);
+        up_read(&_mirror_sets_lock);
+}
+
+/*-----------------------------------------------------------------
+ * Target functions
+ *---------------------------------------------------------------*/
+static struct mirror_set *alloc_context(unsigned int nr_mirrors,
+                                        uint32_t region_size,
+                                        struct dm_target *ti,
+                                        struct dirty_log *dl)
+{
+        size_t len;
+        struct mirror_set *ms = NULL;
+
+        if (array_too_big(sizeof(*ms), sizeof(ms->mirror[0]), nr_mirrors))
+                return NULL;
+
+        len = sizeof(*ms) + (sizeof(ms->mirror[0]) * nr_mirrors);
+
+        ms = kmalloc(len, GFP_KERNEL);
+        if (!ms) {
+                ti->error = "dm-mirror: Cannot allocate mirror context";
+                return NULL;
+        }
+
+        memset(ms, 0, len);
+        spin_lock_init(&ms->lock);
+
+        ms->ti = ti;
+        ms->nr_mirrors = nr_mirrors;
+        ms->nr_regions = dm_sector_div_up(ti->len, region_size);
+        ms->in_sync = 0;
+
+        if (rh_init(&ms->rh, ms, dl, region_size, ms->nr_regions)) {
+                ti->error = "dm-mirror: Error creating dirty region hash";
+                kfree(ms);
+                return NULL;
+        }
+
+        return ms;
+}
+
+static void free_context(struct mirror_set *ms, struct dm_target *ti,
+                         unsigned int m)
+{
+        while (m--)
+                dm_put_device(ti, ms->mirror[m].dev);
+
+        rh_exit(&ms->rh);
+        kfree(ms);
+}
+
+static inline int _check_region_size(struct dm_target *ti, uint32_t size)
+{
+        return !(size % (PAGE_SIZE >> 9) || (size & (size - 1)) ||
+                 size > ti->len);
+}
+
+static int get_mirror(struct mirror_set *ms, struct dm_target *ti,
+                      unsigned int mirror, char **argv)
+{
+        sector_t offset;
+
+        if (sscanf(argv[1], SECTOR_FORMAT, &offset) != 1) {
+                ti->error = "dm-mirror: Invalid offset";
+                return -EINVAL;
+        }
+
+        if (dm_get_device(ti, argv[0], offset, ti->len,
+                          dm_table_get_mode(ti->table),
+                          &ms->mirror[mirror].dev)) {
+                ti->error = "dm-mirror: Device lookup failure";
+                return -ENXIO;
+        }
+
+        ms->mirror[mirror].offset = offset;
+
+        return 0;
+}
+
+static int add_mirror_set(struct mirror_set *ms)
+{
+        down_write(&_mirror_sets_lock);
+        list_add_tail(&ms->list, &_mirror_sets);
+        up_write(&_mirror_sets_lock);
+        wake();
+
+        return 0;
+}
+
+static void del_mirror_set(struct mirror_set *ms)
+{
+        down_write(&_mirror_sets_lock);
+        list_del(&ms->list);
+        up_write(&_mirror_sets_lock);
+}
+
+/*
+ * Create dirty log: log_type #log_params <log_params>
+ */
+static struct dirty_log *create_dirty_log(struct dm_target *ti,
+                                          unsigned int argc, char **argv,
+                                          unsigned int *args_used)
+{
+        unsigned int param_count;
+        struct dirty_log *dl;
+
+        if (argc < 2) {
+                ti->error = "dm-mirror: Insufficient mirror log arguments";
+                return NULL;
+        }
+
+        if (sscanf(argv[1], "%u", &param_count) != 1) {
+                ti->error = "dm-mirror: Invalid mirror log argument count";
+                return NULL;
+        }
+
+        *args_used = 2 + param_count;
+
+        if (argc < *args_used) {
+                ti->error = "dm-mirror: Insufficient mirror log arguments";
+                return NULL;
+        }
+
+        dl = dm_create_dirty_log(argv[0], ti, param_count, argv + 2);
+        if (!dl) {
+                ti->error = "dm-mirror: Error creating mirror dirty log";
+                return NULL;
+        }
+
+        if (!_check_region_size(ti, dl->type->get_region_size(dl))) {
+                ti->error = "dm-mirror: Invalid region size";
+                dm_destroy_dirty_log(dl);
+                return NULL;
+        }
+
+        return dl;
+}
+
+/*
+ * Construct a mirror mapping:
+ *
+ * log_type #log_params <log_params>
+ * #mirrors [mirror_path offset]{2,}
+ *
+ * log_type is "core" or "disk"
+ * #log_params is between 1 and 3
+ */
+#define DM_IO_PAGES 64
+static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
+{
+        int r;
+        unsigned int nr_mirrors, m, args_used;
+        struct mirror_set *ms;
+        struct dirty_log *dl;
+
+        dl = create_dirty_log(ti, argc, argv, &args_used);
+        if (!dl)
+                return -EINVAL;
+
+        argv += args_used;
+        argc -= args_used;
+
+        if (!argc || sscanf(argv[0], "%u", &nr_mirrors) != 1 ||
+            nr_mirrors < 2 || nr_mirrors > KCOPYD_MAX_REGIONS + 1) {
+                ti->error = "dm-mirror: Invalid number of mirrors";
+                dm_destroy_dirty_log(dl);
+                return -EINVAL;
+        }
+
+        argv++, argc--;
+
+        if (argc != nr_mirrors * 2) {
+                ti->error = "dm-mirror: Wrong number of mirror arguments";
+                dm_destroy_dirty_log(dl);
+                return -EINVAL;
+        }
+
+        ms = alloc_context(nr_mirrors, dl->type->get_region_size(dl), ti, dl);
+        if (!ms) {
+                dm_destroy_dirty_log(dl);
+                return -ENOMEM;
+        }
+
+        /* Get the mirror parameter sets */
+        for (m = 0; m < nr_mirrors; m++) {
+                r = get_mirror(ms, ti, m, argv);
+                if (r) {
+                        free_context(ms, ti, m);
+                        return r;
+                }
+                argv += 2;
+                argc -= 2;
+        }
+
+        ti->private = ms;
+
+        r = kcopyd_client_create(DM_IO_PAGES, &ms->kcopyd_client);
+        if (r) {
+                free_context(ms, ti, ms->nr_mirrors);
+                return r;
+        }
+
+        add_mirror_set(ms);
+        return 0;
+}
+
+static void mirror_dtr(struct dm_target *ti)
+{
+        struct mirror_set *ms = (struct mirror_set *) ti->private;
+
+        del_mirror_set(ms);
+        kcopyd_client_destroy(ms->kcopyd_client);
+        free_context(ms, ti, ms->nr_mirrors);
+}
+
+static void queue_bio(struct mirror_set *ms, struct bio *bio, int rw)
+{
+        int should_wake = 0;
+        struct bio_list *bl;
+
+        bl = (rw == WRITE) ? &ms->writes : &ms->reads;
+        spin_lock(&ms->lock);
+        should_wake = !(bl->head);
+        bio_list_add(bl, bio);
+        spin_unlock(&ms->lock);
+
+        if (should_wake)
+                wake();
+}
+
+/*
+ * Mirror mapping function
+ */
+static int mirror_map(struct dm_target *ti, struct bio *bio,
+                      union map_info *map_context)
+{
+        int r, rw = bio_rw(bio);
+        struct mirror *m;
+        struct mirror_set *ms = ti->private;
+
+        map_context->ll = bio->bi_sector >> ms->rh.region_shift;
+
+        if (rw == WRITE) {
+                queue_bio(ms, bio, rw);
+                return 0;
+        }
+
+        r = ms->rh.log->type->in_sync(ms->rh.log,
+                                      bio_to_region(&ms->rh, bio), 0);
+        if (r < 0 && r != -EWOULDBLOCK)
+                return r;
+
+        if (r == -EWOULDBLOCK)  /* FIXME: ugly */
+                r = 0;
+
+        /*
+         * We don't want to fast track a recovery just for a read
+         * ahead.  So we just let it silently fail.
+         * FIXME: get rid of this.
+         */
+        if (!r && rw == READA)
+                return -EIO;
+
+        if (!r) {
+                /* Pass this io over to the daemon */
+                queue_bio(ms, bio, rw);
+                return 0;
+        }
+
+        m = choose_mirror(ms, bio->bi_sector);
+        if (!m)
+                return -EIO;
+
+        map_bio(ms, m, bio);
+        return 1;
+}
+
+static int mirror_end_io(struct dm_target *ti, struct bio *bio,
+                         int error, union map_info *map_context)
+{
+        int rw = bio_rw(bio);
+        struct mirror_set *ms = (struct mirror_set *) ti->private;
+        region_t region = map_context->ll;
+
+        /*
+         * We need to dec pending if this was a write.
+         */
+        if (rw == WRITE)
+                rh_dec(&ms->rh, region);
+
+        return 0;
+}
+
+static void mirror_postsuspend(struct dm_target *ti)
+{
+        struct mirror_set *ms = (struct mirror_set *) ti->private;
+        struct dirty_log *log = ms->rh.log;
+
+        rh_stop_recovery(&ms->rh);
+        if (log->type->suspend && log->type->suspend(log))
+                /* FIXME: need better error handling */
+                DMWARN("log suspend failed");
+}
+
+static void mirror_resume(struct dm_target *ti)
+{
+        struct mirror_set *ms = (struct mirror_set *) ti->private;
+        struct dirty_log *log = ms->rh.log;
+        if (log->type->resume && log->type->resume(log))
+                /* FIXME: need better error handling */
+                DMWARN("log resume failed");
+        rh_start_recovery(&ms->rh);
+}
+
+static int mirror_status(struct dm_target *ti, status_type_t type,
+                         char *result, unsigned int maxlen)
+{
+        unsigned int m, sz;
+        struct mirror_set *ms = (struct mirror_set *) ti->private;
+
+        sz = ms->rh.log->type->status(ms->rh.log, type, result, maxlen);
+
+        switch (type) {
+        case STATUSTYPE_INFO:
+                DMEMIT("%d ", ms->nr_mirrors);
+                for (m = 0; m < ms->nr_mirrors; m++)
+                        DMEMIT("%s ", ms->mirror[m].dev->name);
+
+                DMEMIT(SECTOR_FORMAT "/" SECTOR_FORMAT,
+                       ms->rh.log->type->get_sync_count(ms->rh.log),
+                       ms->nr_regions);
+                break;
+
+        case STATUSTYPE_TABLE:
+                DMEMIT("%d ", ms->nr_mirrors);
+                for (m = 0; m < ms->nr_mirrors; m++)
+                        DMEMIT("%s " SECTOR_FORMAT " ",
+                               ms->mirror[m].dev->name, ms->mirror[m].offset);
+        }
+
+        return 0;
+}
+
+static struct target_type mirror_target = {
+        .name    = "mirror",
+        .version = {1, 0, 1},
+        .module  = THIS_MODULE,
+        .ctr     = mirror_ctr,
+        .dtr     = mirror_dtr,
+        .map     = mirror_map,
+        .end_io  = mirror_end_io,
+        .postsuspend = mirror_postsuspend,
+        .resume  = mirror_resume,
+        .status  = mirror_status,
+};
+
+static int __init dm_mirror_init(void)
+{
+        int r;
+
+        r = dm_dirty_log_init();
+        if (r)
+                return r;
+
+        _kmirrord_wq = create_workqueue("kmirrord");
+        if (!_kmirrord_wq) {
+                DMERR("couldn't start kmirrord");
+                dm_dirty_log_exit();
+                return r;
+        }
+        INIT_WORK(&_kmirrord_work, do_work, NULL);
+
+        r = dm_register_target(&mirror_target);
+        if (r < 0) {
+                DMERR("%s: Failed to register mirror target",
+                      mirror_target.name);
+                dm_dirty_log_exit();
+                destroy_workqueue(_kmirrord_wq);
+        }
+
+        return r;
+}
+
+static void __exit dm_mirror_exit(void)
+{
+        int r;
+
+        r = dm_unregister_target(&mirror_target);
+        if (r < 0)
+                DMERR("%s: unregister failed %d", mirror_target.name, r);
+
+        destroy_workqueue(_kmirrord_wq);
+        dm_dirty_log_exit();
+}
+
+/* Module hooks */
+module_init(dm_mirror_init);
+module_exit(dm_mirror_exit);
+
+MODULE_DESCRIPTION(DM_NAME " mirror target");
+MODULE_AUTHOR("Joe Thornber");
+MODULE_LICENSE("GPL");