Merge tag 'dm-3.5-changes-1' of git://git.kernel.org/pub/scm/linux/kernel/git/agk/linux-dm

Pull device-mapper updates from Alasdair G Kergon:
 "Improve multipath's retrying mechanism in some defined circumstances
  and provide a simple reserve/release mechanism for userspace tools to
  access thin provisioning metadata while the pool is in use."

* tag 'dm-3.5-changes-1' of git://git.kernel.org/pub/scm/linux/kernel/git/agk/linux-dm:
  dm thin: provide userspace access to pool metadata
  dm thin: use slab mempools
  dm mpath: allow ioctls to trigger pg init
  dm mpath: delay retry of bypassed pg
  dm mpath: reduce size of struct multipath

6 files changed, 322 insertions, 90 deletions

diff --git a/Documentation/device-mapper/thin-provisioning.txt b/Documentation/device-mapper/thin-provisioning.txt
index 3370bc4d7b98..f5cfc62b7ad3 100644
--- a/Documentation/device-mapper/thin-provisioning.txt
+++ b/Documentation/device-mapper/thin-provisioning.txt
@@ -287,6 +287,17 @@ iii) Messages
         the current transaction id is when you change it with this
         compare-and-swap message.
 
+    reserve_metadata_snap
+
+        Reserve a copy of the data mapping btree for use by userland.
+        This allows userland to inspect the mappings as they were when
+        this message was executed.  Use the pool's status command to
+        get the root block associated with the metadata snapshot.
+
+    release_metadata_snap
+
+        Release a previously reserved copy of the data mapping btree.
+
 'thin' target
 -------------
 
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 754f38f8a692..638dae048b4f 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -18,6 +18,7 @@
 #include <linux/slab.h>
 #include <linux/time.h>
 #include <linux/workqueue.h>
+#include <linux/delay.h>
 #include <scsi/scsi_dh.h>
 #include <linux/atomic.h>
 
@@ -61,11 +62,11 @@ struct multipath {
         struct list_head list;
         struct dm_target *ti;
 
-        spinlock_t lock;
-
         const char *hw_handler_name;
         char *hw_handler_params;
 
+        spinlock_t lock;
+
         unsigned nr_priority_groups;
         struct list_head priority_groups;
 
@@ -81,16 +82,17 @@ struct multipath {
         struct priority_group *next_pg; /* Switch to this PG if set */
         unsigned repeat_count;          /* I/Os left before calling PS again */
 
-        unsigned queue_io;              /* Must we queue all I/O? */
-        unsigned queue_if_no_path;      /* Queue I/O if last path fails? */
-        unsigned saved_queue_if_no_path;/* Saved state during suspension */
+        unsigned queue_io:1;            /* Must we queue all I/O? */
+        unsigned queue_if_no_path:1;    /* Queue I/O if last path fails? */
+        unsigned saved_queue_if_no_path:1; /* Saved state during suspension */
+
         unsigned pg_init_retries;       /* Number of times to retry pg_init */
         unsigned pg_init_count;         /* Number of times pg_init called */
         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
 
+        unsigned queue_size;
         struct work_struct process_queued_ios;
         struct list_head queued_ios;
-        unsigned queue_size;
 
         struct work_struct trigger_event;
 
@@ -328,14 +330,18 @@ static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
         /*
          * Loop through priority groups until we find a valid path.
          * First time we skip PGs marked 'bypassed'.
-         * Second time we only try the ones we skipped.
+         * Second time we only try the ones we skipped, but set
+         * pg_init_delay_retry so we do not hammer controllers.
          */
         do {
                 list_for_each_entry(pg, &m->priority_groups, list) {
                         if (pg->bypassed == bypassed)
                                 continue;
-                        if (!__choose_path_in_pg(m, pg, nr_bytes))
+                        if (!__choose_path_in_pg(m, pg, nr_bytes)) {
+                                if (!bypassed)
+                                        m->pg_init_delay_retry = 1;
                                 return;
+                        }
                 }
         } while (bypassed--);
 
@@ -481,9 +487,6 @@ static void process_queued_ios(struct work_struct *work)
 
         spin_lock_irqsave(&m->lock, flags);
 
-        if (!m->queue_size)
-                goto out;
-
         if (!m->current_pgpath)
                 __choose_pgpath(m, 0);
 
@@ -496,7 +499,6 @@ static void process_queued_ios(struct work_struct *work)
         if (m->pg_init_required && !m->pg_init_in_progress && pgpath)
                 __pg_init_all_paths(m);
 
-out:
         spin_unlock_irqrestore(&m->lock, flags);
         if (!must_queue)
                 dispatch_queued_ios(m);
@@ -1517,11 +1519,16 @@ out:
 static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
                            unsigned long arg)
 {
-        struct multipath *m = (struct multipath *) ti->private;
-        struct block_device *bdev = NULL;
-        fmode_t mode = 0;
+        struct multipath *m = ti->private;
+        struct block_device *bdev;
+        fmode_t mode;
         unsigned long flags;
-        int r = 0;
+        int r;
+
+again:
+        bdev = NULL;
+        mode = 0;
+        r = 0;
 
         spin_lock_irqsave(&m->lock, flags);
 
@@ -1546,6 +1553,12 @@ static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
         if (!r && ti->len != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT)
                 r = scsi_verify_blk_ioctl(NULL, cmd);
 
+        if (r == -EAGAIN && !fatal_signal_pending(current)) {
+                queue_work(kmultipathd, &m->process_queued_ios);
+                msleep(10);
+                goto again;
+        }
+
         return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
 }
 
@@ -1643,7 +1656,7 @@ out:
  *---------------------------------------------------------------*/
 static struct target_type multipath_target = {
         .name = "multipath",
-        .version = {1, 3, 0},
+        .version = {1, 4, 0},
         .module = THIS_MODULE,
         .ctr = multipath_ctr,
         .dtr = multipath_dtr,
diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
index 737d38865b69..3e2907f0bc46 100644
--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -1082,12 +1082,89 @@ int dm_pool_get_metadata_transaction_id(struct dm_pool_metadata *pmd,
         return 0;
 }
 
-static int __get_held_metadata_root(struct dm_pool_metadata *pmd,
-                                    dm_block_t *result)
+static int __reserve_metadata_snap(struct dm_pool_metadata *pmd)
+{
+        int r, inc;
+        struct thin_disk_superblock *disk_super;
+        struct dm_block *copy, *sblock;
+        dm_block_t held_root;
+
+        /*
+         * Copy the superblock.
+         */
+        dm_sm_inc_block(pmd->metadata_sm, THIN_SUPERBLOCK_LOCATION);
+        r = dm_tm_shadow_block(pmd->tm, THIN_SUPERBLOCK_LOCATION,
+                               &sb_validator, &copy, &inc);
+        if (r)
+                return r;
+
+        BUG_ON(!inc);
+
+        held_root = dm_block_location(copy);
+        disk_super = dm_block_data(copy);
+
+        if (le64_to_cpu(disk_super->held_root)) {
+                DMWARN("Pool metadata snapshot already exists: release this before taking another.");
+
+                dm_tm_dec(pmd->tm, held_root);
+                dm_tm_unlock(pmd->tm, copy);
+                pmd->need_commit = 1;
+
+                return -EBUSY;
+        }
+
+        /*
+         * Wipe the spacemap since we're not publishing this.
+         */
+        memset(&disk_super->data_space_map_root, 0,
+               sizeof(disk_super->data_space_map_root));
+        memset(&disk_super->metadata_space_map_root, 0,
+               sizeof(disk_super->metadata_space_map_root));
+
+        /*
+         * Increment the data structures that need to be preserved.
+         */
+        dm_tm_inc(pmd->tm, le64_to_cpu(disk_super->data_mapping_root));
+        dm_tm_inc(pmd->tm, le64_to_cpu(disk_super->device_details_root));
+        dm_tm_unlock(pmd->tm, copy);
+
+        /*
+         * Write the held root into the superblock.
+         */
+        r = dm_bm_write_lock(pmd->bm, THIN_SUPERBLOCK_LOCATION,
+                             &sb_validator, &sblock);
+        if (r) {
+                dm_tm_dec(pmd->tm, held_root);
+                pmd->need_commit = 1;
+                return r;
+        }
+
+        disk_super = dm_block_data(sblock);
+        disk_super->held_root = cpu_to_le64(held_root);
+        dm_bm_unlock(sblock);
+
+        pmd->need_commit = 1;
+
+        return 0;
+}
+
+int dm_pool_reserve_metadata_snap(struct dm_pool_metadata *pmd)
+{
+        int r;
+
+        down_write(&pmd->root_lock);
+        r = __reserve_metadata_snap(pmd);
+        up_write(&pmd->root_lock);
+
+        return r;
+}
+
+static int __release_metadata_snap(struct dm_pool_metadata *pmd)
 {
         int r;
         struct thin_disk_superblock *disk_super;
-        struct dm_block *sblock;
+        struct dm_block *sblock, *copy;
+        dm_block_t held_root;
 
         r = dm_bm_write_lock(pmd->bm, THIN_SUPERBLOCK_LOCATION,
                              &sb_validator, &sblock);
@@ -1095,18 +1172,65 @@ static int __get_held_metadata_root(struct dm_pool_metadata *pmd,
                 return r;
 
         disk_super = dm_block_data(sblock);
+        held_root = le64_to_cpu(disk_super->held_root);
+        disk_super->held_root = cpu_to_le64(0);
+        pmd->need_commit = 1;
+
+        dm_bm_unlock(sblock);
+
+        if (!held_root) {
+                DMWARN("No pool metadata snapshot found: nothing to release.");
+                return -EINVAL;
+        }
+
+        r = dm_tm_read_lock(pmd->tm, held_root, &sb_validator, &copy);
+        if (r)
+                return r;
+
+        disk_super = dm_block_data(copy);
+        dm_sm_dec_block(pmd->metadata_sm, le64_to_cpu(disk_super->data_mapping_root));
+        dm_sm_dec_block(pmd->metadata_sm, le64_to_cpu(disk_super->device_details_root));
+        dm_sm_dec_block(pmd->metadata_sm, held_root);
+
+        return dm_tm_unlock(pmd->tm, copy);
+}
+
+int dm_pool_release_metadata_snap(struct dm_pool_metadata *pmd)
+{
+        int r;
+
+        down_write(&pmd->root_lock);
+        r = __release_metadata_snap(pmd);
+        up_write(&pmd->root_lock);
+
+        return r;
+}
+
+static int __get_metadata_snap(struct dm_pool_metadata *pmd,
+                               dm_block_t *result)
+{
+        int r;
+        struct thin_disk_superblock *disk_super;
+        struct dm_block *sblock;
+
+        r = dm_bm_read_lock(pmd->bm, THIN_SUPERBLOCK_LOCATION,
+                            &sb_validator, &sblock);
+        if (r)
+                return r;
+
+        disk_super = dm_block_data(sblock);
         *result = le64_to_cpu(disk_super->held_root);
 
         return dm_bm_unlock(sblock);
 }
 
-int dm_pool_get_held_metadata_root(struct dm_pool_metadata *pmd,
-                                   dm_block_t *result)
+int dm_pool_get_metadata_snap(struct dm_pool_metadata *pmd,
+                              dm_block_t *result)
 {
         int r;
 
         down_read(&pmd->root_lock);
-        r = __get_held_metadata_root(pmd, result);
+        r = __get_metadata_snap(pmd, result);
         up_read(&pmd->root_lock);
 
         return r;
diff --git a/drivers/md/dm-thin-metadata.h b/drivers/md/dm-thin-metadata.h
index ed4725e67c96..b88918ccdaf6 100644
--- a/drivers/md/dm-thin-metadata.h
+++ b/drivers/md/dm-thin-metadata.h
@@ -90,11 +90,18 @@ int dm_pool_get_metadata_transaction_id(struct dm_pool_metadata *pmd,
 
 /*
  * Hold/get root for userspace transaction.
+ *
+ * The metadata snapshot is a copy of the current superblock (minus the
+ * space maps).  Userland can access the data structures for READ
+ * operations only.  A small performance hit is incurred by providing this
+ * copy of the metadata to userland due to extra copy-on-write operations
+ * on the metadata nodes.  Release this as soon as you finish with it.
  */
-int dm_pool_hold_metadata_root(struct dm_pool_metadata *pmd);
+int dm_pool_reserve_metadata_snap(struct dm_pool_metadata *pmd);
+int dm_pool_release_metadata_snap(struct dm_pool_metadata *pmd);
 
-int dm_pool_get_held_metadata_root(struct dm_pool_metadata *pmd,
-                                   dm_block_t *result);
+int dm_pool_get_metadata_snap(struct dm_pool_metadata *pmd,
+                              dm_block_t *result);
 
 /*
  * Actions on a single virtual device.
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index eb3d138ff55a..37fdaf81bd1f 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -111,7 +111,7 @@ struct cell_key {
         dm_block_t block;
 };
 
-struct cell {
+struct dm_bio_prison_cell {
         struct hlist_node list;
         struct bio_prison *prison;
         struct cell_key key;
@@ -141,6 +141,8 @@ static uint32_t calc_nr_buckets(unsigned nr_cells)
         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.
@@ -157,8 +159,7 @@ static struct bio_prison *prison_create(unsigned nr_cells)
                 return NULL;
 
         spin_lock_init(&prison->lock);
-        prison->cell_pool = mempool_create_kmalloc_pool(nr_cells,
-                                                        sizeof(struct cell));
+        prison->cell_pool = mempool_create_slab_pool(nr_cells, _cell_cache);
         if (!prison->cell_pool) {
                 kfree(prison);
                 return NULL;
@@ -194,10 +195,10 @@ static int keys_equal(struct cell_key *lhs, struct cell_key *rhs)
                        (lhs->block == rhs->block);
 }
 
-static struct cell *__search_bucket(struct hlist_head *bucket,
-                                    struct cell_key *key)
+static struct dm_bio_prison_cell *__search_bucket(struct hlist_head *bucket,
+                                                  struct cell_key *key)
 {
-        struct cell *cell;
+        struct dm_bio_prison_cell *cell;
         struct hlist_node *tmp;
 
         hlist_for_each_entry(cell, tmp, bucket, list)
@@ -214,12 +215,12 @@ static struct cell *__search_bucket(struct hlist_head *bucket,
  * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
  */
 static int bio_detain(struct bio_prison *prison, struct cell_key *key,
-                      struct bio *inmate, struct cell **ref)
+                      struct bio *inmate, struct dm_bio_prison_cell **ref)
 {
         int r = 1;
         unsigned long flags;
         uint32_t hash = hash_key(prison, key);
-        struct cell *cell, *cell2;
+        struct dm_bio_prison_cell *cell, *cell2;
 
         BUG_ON(hash > prison->nr_buckets);
 
@@ -273,7 +274,7 @@ out:
 /*
  * @inmates must have been initialised prior to this call
  */
-static void __cell_release(struct cell *cell, struct bio_list *inmates)
+static void __cell_release(struct dm_bio_prison_cell *cell, struct bio_list *inmates)
 {
         struct bio_prison *prison = cell->prison;
 
@@ -287,7 +288,7 @@ static void __cell_release(struct cell *cell, struct bio_list *inmates)
         mempool_free(cell, prison->cell_pool);
 }
 
-static void cell_release(struct cell *cell, struct bio_list *bios)
+static void cell_release(struct dm_bio_prison_cell *cell, struct bio_list *bios)
 {
         unsigned long flags;
         struct bio_prison *prison = cell->prison;
@@ -303,7 +304,7 @@ static void cell_release(struct cell *cell, struct bio_list *bios)
  * bio may be in the cell.  This function releases the cell, and also does
  * a sanity check.
  */
-static void __cell_release_singleton(struct cell *cell, struct bio *bio)
+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));
@@ -311,7 +312,7 @@ static void __cell_release_singleton(struct cell *cell, struct bio *bio)
         __cell_release(cell, NULL);
 }
 
-static void cell_release_singleton(struct cell *cell, struct bio *bio)
+static void cell_release_singleton(struct dm_bio_prison_cell *cell, struct bio *bio)
 {
         unsigned long flags;
         struct bio_prison *prison = cell->prison;
@@ -324,7 +325,8 @@ static void cell_release_singleton(struct cell *cell, struct bio *bio)
 /*
  * Sometimes we don't want the holder, just the additional bios.
  */
-static void __cell_release_no_holder(struct cell *cell, struct bio_list *inmates)
+static void __cell_release_no_holder(struct dm_bio_prison_cell *cell,
+                                     struct bio_list *inmates)
 {
         struct bio_prison *prison = cell->prison;
 
@@ -334,7 +336,8 @@ static void __cell_release_no_holder(struct cell *cell, struct bio_list *inmates
         mempool_free(cell, prison->cell_pool);
 }
 
-static void cell_release_no_holder(struct cell *cell, struct bio_list *inmates)
+static void cell_release_no_holder(struct dm_bio_prison_cell *cell,
+                                   struct bio_list *inmates)
 {
         unsigned long flags;
         struct bio_prison *prison = cell->prison;
@@ -344,7 +347,7 @@ static void cell_release_no_holder(struct cell *cell, struct bio_list *inmates)
         spin_unlock_irqrestore(&prison->lock, flags);
 }
 
-static void cell_error(struct cell *cell)
+static void cell_error(struct dm_bio_prison_cell *cell)
 {
         struct bio_prison *prison = cell->prison;
         struct bio_list bios;
@@ -491,7 +494,7 @@ static void build_virtual_key(struct dm_thin_device *td, dm_block_t b,
  * also provides the interface for creating and destroying internal
  * devices.
  */
-struct new_mapping;
+struct dm_thin_new_mapping;
 
 struct pool_features {
         unsigned zero_new_blocks:1;
@@ -537,7 +540,7 @@ struct pool {
         struct deferred_set shared_read_ds;
         struct deferred_set all_io_ds;
 
-        struct new_mapping *next_mapping;
+        struct dm_thin_new_mapping *next_mapping;
         mempool_t *mapping_pool;
         mempool_t *endio_hook_pool;
 };
@@ -630,11 +633,11 @@ static struct pool *__pool_table_lookup_metadata_dev(struct block_device *md_dev
 
 /*----------------------------------------------------------------*/
 
-struct endio_hook {
+struct dm_thin_endio_hook {
         struct thin_c *tc;
         struct deferred_entry *shared_read_entry;
         struct deferred_entry *all_io_entry;
-        struct new_mapping *overwrite_mapping;
+        struct dm_thin_new_mapping *overwrite_mapping;
 };
 
 static void __requeue_bio_list(struct thin_c *tc, struct bio_list *master)
@@ -647,7 +650,8 @@ static void __requeue_bio_list(struct thin_c *tc, struct bio_list *master)
         bio_list_init(master);
 
         while ((bio = bio_list_pop(&bios))) {
-                struct endio_hook *h = dm_get_mapinfo(bio)->ptr;
+                struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;
+
                 if (h->tc == tc)
                         bio_endio(bio, DM_ENDIO_REQUEUE);
                 else
@@ -736,7 +740,7 @@ static void wake_worker(struct pool *pool)
 /*
  * Bio endio functions.
  */
-struct new_mapping {
+struct dm_thin_new_mapping {
         struct list_head list;
 
         unsigned quiesced:1;
@@ -746,7 +750,7 @@ struct new_mapping {
         struct thin_c *tc;
         dm_block_t virt_block;
         dm_block_t data_block;
-        struct cell *cell, *cell2;
+        struct dm_bio_prison_cell *cell, *cell2;
         int err;
 
         /*
@@ -759,7 +763,7 @@ struct new_mapping {
         bio_end_io_t *saved_bi_end_io;
 };
 
-static void __maybe_add_mapping(struct new_mapping *m)
+static void __maybe_add_mapping(struct dm_thin_new_mapping *m)
 {
         struct pool *pool = m->tc->pool;
 
@@ -772,7 +776,7 @@ static void __maybe_add_mapping(struct new_mapping *m)
 static void copy_complete(int read_err, unsigned long write_err, void *context)
 {
         unsigned long flags;
-        struct new_mapping *m = context;
+        struct dm_thin_new_mapping *m = context;
         struct pool *pool = m->tc->pool;
 
         m->err = read_err || write_err ? -EIO : 0;
@@ -786,8 +790,8 @@ static void copy_complete(int read_err, unsigned long write_err, void *context)
 static void overwrite_endio(struct bio *bio, int err)
 {
         unsigned long flags;
-        struct endio_hook *h = dm_get_mapinfo(bio)->ptr;
-        struct new_mapping *m = h->overwrite_mapping;
+        struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;
+        struct dm_thin_new_mapping *m = h->overwrite_mapping;
         struct pool *pool = m->tc->pool;
 
         m->err = err;
@@ -811,7 +815,7 @@ static void overwrite_endio(struct bio *bio, int err)
 /*
  * This sends the bios in the cell back to the deferred_bios list.
  */
-static void cell_defer(struct thin_c *tc, struct cell *cell,
+static void cell_defer(struct thin_c *tc, struct dm_bio_prison_cell *cell,
                        dm_block_t data_block)
 {
         struct pool *pool = tc->pool;
@@ -828,7 +832,7 @@ static void cell_defer(struct thin_c *tc, struct cell *cell,
  * Same as cell_defer above, except it omits one particular detainee,
  * a write bio that covers the block and has already been processed.
  */
-static void cell_defer_except(struct thin_c *tc, struct cell *cell)
+static void cell_defer_except(struct thin_c *tc, struct dm_bio_prison_cell *cell)
 {
         struct bio_list bios;
         struct pool *pool = tc->pool;
@@ -843,7 +847,7 @@ static void cell_defer_except(struct thin_c *tc, struct cell *cell)
         wake_worker(pool);
 }
 
-static void process_prepared_mapping(struct new_mapping *m)
+static void process_prepared_mapping(struct dm_thin_new_mapping *m)
 {
         struct thin_c *tc = m->tc;
         struct bio *bio;
@@ -886,7 +890,7 @@ static void process_prepared_mapping(struct new_mapping *m)
         mempool_free(m, tc->pool->mapping_pool);
 }
 
-static void process_prepared_discard(struct new_mapping *m)
+static void process_prepared_discard(struct dm_thin_new_mapping *m)
 {
         int r;
         struct thin_c *tc = m->tc;
@@ -909,11 +913,11 @@ static void process_prepared_discard(struct new_mapping *m)
 }
 
 static void process_prepared(struct pool *pool, struct list_head *head,
-                             void (*fn)(struct new_mapping *))
+                             void (*fn)(struct dm_thin_new_mapping *))
 {
         unsigned long flags;
         struct list_head maps;
-        struct new_mapping *m, *tmp;
+        struct dm_thin_new_mapping *m, *tmp;
 
         INIT_LIST_HEAD(&maps);
         spin_lock_irqsave(&pool->lock, flags);
@@ -957,9 +961,9 @@ static int ensure_next_mapping(struct pool *pool)
         return pool->next_mapping ? 0 : -ENOMEM;
 }
 
-static struct new_mapping *get_next_mapping(struct pool *pool)
+static struct dm_thin_new_mapping *get_next_mapping(struct pool *pool)
 {
-        struct new_mapping *r = pool->next_mapping;
+        struct dm_thin_new_mapping *r = pool->next_mapping;
 
         BUG_ON(!pool->next_mapping);
 
@@ -971,11 +975,11 @@ static struct new_mapping *get_next_mapping(struct pool *pool)
 static void schedule_copy(struct thin_c *tc, dm_block_t virt_block,
                           struct dm_dev *origin, dm_block_t data_origin,
                           dm_block_t data_dest,
-                          struct cell *cell, struct bio *bio)
+                          struct dm_bio_prison_cell *cell, struct bio *bio)
 {
         int r;
         struct pool *pool = tc->pool;
-        struct new_mapping *m = get_next_mapping(pool);
+        struct dm_thin_new_mapping *m = get_next_mapping(pool);
 
         INIT_LIST_HEAD(&m->list);
         m->quiesced = 0;
@@ -997,7 +1001,8 @@ static void schedule_copy(struct thin_c *tc, dm_block_t virt_block,
          * bio immediately. Otherwise we use kcopyd to clone the data first.
          */
         if (io_overwrites_block(pool, bio)) {
-                struct endio_hook *h = dm_get_mapinfo(bio)->ptr;
+                struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;
+
                 h->overwrite_mapping = m;
                 m->bio = bio;
                 save_and_set_endio(bio, &m->saved_bi_end_io, overwrite_endio);
@@ -1025,7 +1030,7 @@ static void schedule_copy(struct thin_c *tc, dm_block_t virt_block,
 
 static void schedule_internal_copy(struct thin_c *tc, dm_block_t virt_block,
                                    dm_block_t data_origin, dm_block_t data_dest,
-                                   struct cell *cell, struct bio *bio)
+                                   struct dm_bio_prison_cell *cell, struct bio *bio)
 {
         schedule_copy(tc, virt_block, tc->pool_dev,
                       data_origin, data_dest, cell, bio);
@@ -1033,18 +1038,18 @@ static void schedule_internal_copy(struct thin_c *tc, dm_block_t virt_block,
 
 static void schedule_external_copy(struct thin_c *tc, dm_block_t virt_block,
                                    dm_block_t data_dest,
-                                   struct cell *cell, struct bio *bio)
+                                   struct dm_bio_prison_cell *cell, struct bio *bio)
 {
         schedule_copy(tc, virt_block, tc->origin_dev,
                       virt_block, data_dest, cell, bio);
 }
 
 static void schedule_zero(struct thin_c *tc, dm_block_t virt_block,
-                          dm_block_t data_block, struct cell *cell,
+                          dm_block_t data_block, struct dm_bio_prison_cell *cell,
                           struct bio *bio)
 {
         struct pool *pool = tc->pool;
-        struct new_mapping *m = get_next_mapping(pool);
+        struct dm_thin_new_mapping *m = get_next_mapping(pool);
 
         INIT_LIST_HEAD(&m->list);
         m->quiesced = 1;
@@ -1065,12 +1070,12 @@ static void schedule_zero(struct thin_c *tc, dm_block_t virt_block,
                 process_prepared_mapping(m);
 
         else if (io_overwrites_block(pool, bio)) {
-                struct endio_hook *h = dm_get_mapinfo(bio)->ptr;
+                struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;
+
                 h->overwrite_mapping = m;
                 m->bio = bio;
                 save_and_set_endio(bio, &m->saved_bi_end_io, overwrite_endio);
                 remap_and_issue(tc, bio, data_block);
-
         } else {
                 int r;
                 struct dm_io_region to;
@@ -1155,7 +1160,7 @@ static int alloc_data_block(struct thin_c *tc, dm_block_t *result)
  */
 static void retry_on_resume(struct bio *bio)
 {
-        struct endio_hook *h = dm_get_mapinfo(bio)->ptr;
+        struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;
         struct thin_c *tc = h->tc;
         struct pool *pool = tc->pool;
         unsigned long flags;
@@ -1165,7 +1170,7 @@ static void retry_on_resume(struct bio *bio)
         spin_unlock_irqrestore(&pool->lock, flags);
 }
 
-static void no_space(struct cell *cell)
+static void no_space(struct dm_bio_prison_cell *cell)
 {
         struct bio *bio;
         struct bio_list bios;
@@ -1182,11 +1187,11 @@ static void process_discard(struct thin_c *tc, struct bio *bio)
         int r;
         unsigned long flags;
         struct pool *pool = tc->pool;
-        struct cell *cell, *cell2;
+        struct dm_bio_prison_cell *cell, *cell2;
         struct cell_key key, key2;
         dm_block_t block = get_bio_block(tc, bio);
         struct dm_thin_lookup_result lookup_result;
-        struct new_mapping *m;
+        struct dm_thin_new_mapping *m;
 
         build_virtual_key(tc->td, block, &key);
         if (bio_detain(tc->pool->prison, &key, bio, &cell))
@@ -1263,7 +1268,7 @@ static void process_discard(struct thin_c *tc, struct bio *bio)
 static void break_sharing(struct thin_c *tc, struct bio *bio, dm_block_t block,
                           struct cell_key *key,
                           struct dm_thin_lookup_result *lookup_result,
-                          struct cell *cell)
+                          struct dm_bio_prison_cell *cell)
 {
         int r;
         dm_block_t data_block;
@@ -1290,7 +1295,7 @@ static void process_shared_bio(struct thin_c *tc, struct bio *bio,
                                dm_block_t block,
                                struct dm_thin_lookup_result *lookup_result)
 {
-        struct cell *cell;
+        struct dm_bio_prison_cell *cell;
         struct pool *pool = tc->pool;
         struct cell_key key;
 
@@ -1305,7 +1310,7 @@ static void process_shared_bio(struct thin_c *tc, struct bio *bio,
         if (bio_data_dir(bio) == WRITE)
                 break_sharing(tc, bio, block, &key, lookup_result, cell);
         else {
-                struct endio_hook *h = dm_get_mapinfo(bio)->ptr;
+                struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;
 
                 h->shared_read_entry = ds_inc(&pool->shared_read_ds);
 
@@ -1315,7 +1320,7 @@ static void process_shared_bio(struct thin_c *tc, struct bio *bio,
 }
 
 static void provision_block(struct thin_c *tc, struct bio *bio, dm_block_t block,
-                            struct cell *cell)
+                            struct dm_bio_prison_cell *cell)
 {
         int r;
         dm_block_t data_block;
@@ -1363,7 +1368,7 @@ static void process_bio(struct thin_c *tc, struct bio *bio)
 {
         int r;
         dm_block_t block = get_bio_block(tc, bio);
-        struct cell *cell;
+        struct dm_bio_prison_cell *cell;
         struct cell_key key;
         struct dm_thin_lookup_result lookup_result;
 
@@ -1432,7 +1437,7 @@ static void process_deferred_bios(struct pool *pool)
         spin_unlock_irqrestore(&pool->lock, flags);
 
         while ((bio = bio_list_pop(&bios))) {
-                struct endio_hook *h = dm_get_mapinfo(bio)->ptr;
+                struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;
                 struct thin_c *tc = h->tc;
 
                 /*
@@ -1522,10 +1527,10 @@ static void thin_defer_bio(struct thin_c *tc, struct bio *bio)
         wake_worker(pool);
 }
 
-static struct endio_hook *thin_hook_bio(struct thin_c *tc, struct bio *bio)
+static struct dm_thin_endio_hook *thin_hook_bio(struct thin_c *tc, struct bio *bio)
 {
         struct pool *pool = tc->pool;
-        struct endio_hook *h = mempool_alloc(pool->endio_hook_pool, GFP_NOIO);
+        struct dm_thin_endio_hook *h = mempool_alloc(pool->endio_hook_pool, GFP_NOIO);
 
         h->tc = tc;
         h->shared_read_entry = NULL;
@@ -1687,6 +1692,9 @@ static void __pool_destroy(struct pool *pool)
         kfree(pool);
 }
 
+static struct kmem_cache *_new_mapping_cache;
+static struct kmem_cache *_endio_hook_cache;
+
 static struct pool *pool_create(struct mapped_device *pool_md,
                                 struct block_device *metadata_dev,
                                 unsigned long block_size, char **error)
@@ -1755,16 +1763,16 @@ static struct pool *pool_create(struct mapped_device *pool_md,
         ds_init(&pool->all_io_ds);
 
         pool->next_mapping = NULL;
-        pool->mapping_pool =
-                mempool_create_kmalloc_pool(MAPPING_POOL_SIZE, sizeof(struct new_mapping));
+        pool->mapping_pool = mempool_create_slab_pool(MAPPING_POOL_SIZE,
+                                                      _new_mapping_cache);
         if (!pool->mapping_pool) {
                 *error = "Error creating pool's mapping mempool";
                 err_p = ERR_PTR(-ENOMEM);
                 goto bad_mapping_pool;
         }
 
-        pool->endio_hook_pool =
-                mempool_create_kmalloc_pool(ENDIO_HOOK_POOL_SIZE, sizeof(struct endio_hook));
+        pool->endio_hook_pool = mempool_create_slab_pool(ENDIO_HOOK_POOL_SIZE,
+                                                         _endio_hook_cache);
         if (!pool->endio_hook_pool) {
                 *error = "Error creating pool's endio_hook mempool";
                 err_p = ERR_PTR(-ENOMEM);
@@ -2276,6 +2284,36 @@ static int process_set_transaction_id_mesg(unsigned argc, char **argv, struct po
         return 0;
 }
 
+static int process_reserve_metadata_snap_mesg(unsigned argc, char **argv, struct pool *pool)
+{
+        int r;
+
+        r = check_arg_count(argc, 1);
+        if (r)
+                return r;
+
+        r = dm_pool_reserve_metadata_snap(pool->pmd);
+        if (r)
+                DMWARN("reserve_metadata_snap message failed.");
+
+        return r;
+}
+
+static int process_release_metadata_snap_mesg(unsigned argc, char **argv, struct pool *pool)
+{
+        int r;
+
+        r = check_arg_count(argc, 1);
+        if (r)
+                return r;
+
+        r = dm_pool_release_metadata_snap(pool->pmd);
+        if (r)
+                DMWARN("release_metadata_snap message failed.");
+
+        return r;
+}
+
 /*
  * Messages supported:
  *   create_thin        <dev_id>
@@ -2283,6 +2321,8 @@ static int process_set_transaction_id_mesg(unsigned argc, char **argv, struct po
  *   delete             <dev_id>
  *   trim               <dev_id> <new_size_in_sectors>
  *   set_transaction_id <current_trans_id> <new_trans_id>
+ *   reserve_metadata_snap
+ *   release_metadata_snap
  */
 static int pool_message(struct dm_target *ti, unsigned argc, char **argv)
 {
@@ -2302,6 +2342,12 @@ static int pool_message(struct dm_target *ti, unsigned argc, char **argv)
         else if (!strcasecmp(argv[0], "set_transaction_id"))
                 r = process_set_transaction_id_mesg(argc, argv, pool);
 
+        else if (!strcasecmp(argv[0], "reserve_metadata_snap"))
+                r = process_reserve_metadata_snap_mesg(argc, argv, pool);
+
+        else if (!strcasecmp(argv[0], "release_metadata_snap"))
+                r = process_release_metadata_snap_mesg(argc, argv, pool);
+
         else
                 DMWARN("Unrecognised thin pool target message received: %s", argv[0]);
 
@@ -2361,7 +2407,7 @@ static int pool_status(struct dm_target *ti, status_type_t type,
                 if (r)
                         return r;
 
-                r = dm_pool_get_held_metadata_root(pool->pmd, &held_root);
+                r = dm_pool_get_metadata_snap(pool->pmd, &held_root);
                 if (r)
                         return r;
 
@@ -2457,7 +2503,7 @@ static struct target_type pool_target = {
         .name = "thin-pool",
         .features = DM_TARGET_SINGLETON | DM_TARGET_ALWAYS_WRITEABLE |
                     DM_TARGET_IMMUTABLE,
-        .version = {1, 1, 0},
+        .version = {1, 2, 0},
         .module = THIS_MODULE,
         .ctr = pool_ctr,
         .dtr = pool_dtr,
@@ -2613,9 +2659,9 @@ static int thin_endio(struct dm_target *ti,
                       union map_info *map_context)
 {
         unsigned long flags;
-        struct endio_hook *h = map_context->ptr;
+        struct dm_thin_endio_hook *h = map_context->ptr;
         struct list_head work;
-        struct new_mapping *m, *tmp;
+        struct dm_thin_new_mapping *m, *tmp;
         struct pool *pool = h->tc->pool;
 
         if (h->shared_read_entry) {
@@ -2755,7 +2801,32 @@ static int __init dm_thin_init(void)
 
         r = dm_register_target(&pool_target);
         if (r)
-                dm_unregister_target(&thin_target);
+                goto bad_pool_target;
+
+        r = -ENOMEM;
+
+        _cell_cache = KMEM_CACHE(dm_bio_prison_cell, 0);
+        if (!_cell_cache)
+                goto bad_cell_cache;
+
+        _new_mapping_cache = KMEM_CACHE(dm_thin_new_mapping, 0);
+        if (!_new_mapping_cache)
+                goto bad_new_mapping_cache;
+
+        _endio_hook_cache = KMEM_CACHE(dm_thin_endio_hook, 0);
+        if (!_endio_hook_cache)
+                goto bad_endio_hook_cache;
+
+        return 0;
+
+bad_endio_hook_cache:
+        kmem_cache_destroy(_new_mapping_cache);
+bad_new_mapping_cache:
+        kmem_cache_destroy(_cell_cache);
+bad_cell_cache:
+        dm_unregister_target(&pool_target);
+bad_pool_target:
+        dm_unregister_target(&thin_target);
 
         return r;
 }
@@ -2764,6 +2835,10 @@ static void dm_thin_exit(void)
 {
         dm_unregister_target(&thin_target);
         dm_unregister_target(&pool_target);
+
+        kmem_cache_destroy(_cell_cache);
+        kmem_cache_destroy(_new_mapping_cache);
+        kmem_cache_destroy(_endio_hook_cache);
 }
 
 module_init(dm_thin_init);
diff --git a/drivers/md/persistent-data/dm-transaction-manager.c b/drivers/md/persistent-data/dm-transaction-manager.c
index 6f8d38747d7f..400fe144c0cd 100644
--- a/drivers/md/persistent-data/dm-transaction-manager.c
+++ b/drivers/md/persistent-data/dm-transaction-manager.c
@@ -249,6 +249,7 @@ int dm_tm_shadow_block(struct dm_transaction_manager *tm, dm_block_t orig,
 
         return r;
 }
+EXPORT_SYMBOL_GPL(dm_tm_shadow_block);
 
 int dm_tm_read_lock(struct dm_transaction_manager *tm, dm_block_t b,
                     struct dm_block_validator *v,
@@ -259,6 +260,7 @@ int dm_tm_read_lock(struct dm_transaction_manager *tm, dm_block_t b,
 
         return dm_bm_read_lock(tm->bm, b, v, blk);
 }
+EXPORT_SYMBOL_GPL(dm_tm_read_lock);
 
 int dm_tm_unlock(struct dm_transaction_manager *tm, struct dm_block *b)
 {