diff --git a/Documentation/device-mapper/dm-raid.txt b/Documentation/device-mapper/dm-raid.txt
index cb12af3b51c21b3b11674fb9b15312c9cee827cb..df2d636b60880cb36c105f68c953d60e50110c77 100644
--- a/Documentation/device-mapper/dm-raid.txt
+++ b/Documentation/device-mapper/dm-raid.txt
@@ -209,6 +209,37 @@ include:
 	"repair" - Initiate a repair of the array.
 	"reshape"- Currently unsupported (-EINVAL).
 
+
+Discard Support
+---------------
+The implementation of discard support among hardware vendors varies.
+When a block is discarded, some storage devices will return zeroes when
+the block is read.  These devices set the 'discard_zeroes_data'
+attribute.  Other devices will return random data.  Confusingly, some
+devices that advertise 'discard_zeroes_data' will not reliably return
+zeroes when discarded blocks are read!  Since RAID 4/5/6 uses blocks
+from a number of devices to calculate parity blocks and (for performance
+reasons) relies on 'discard_zeroes_data' being reliable, it is important
+that the devices be consistent.  Blocks may be discarded in the middle
+of a RAID 4/5/6 stripe and if subsequent read results are not
+consistent, the parity blocks may be calculated differently at any time;
+making the parity blocks useless for redundancy.  It is important to
+understand how your hardware behaves with discards if you are going to
+enable discards with RAID 4/5/6.
+
+Since the behavior of storage devices is unreliable in this respect,
+even when reporting 'discard_zeroes_data', by default RAID 4/5/6
+discard support is disabled -- this ensures data integrity at the
+expense of losing some performance.
+
+Storage devices that properly support 'discard_zeroes_data' are
+increasingly whitelisted in the kernel and can thus be trusted.
+
+For trusted devices, the following dm-raid module parameter can be set
+to safely enable discard support for RAID 4/5/6:
+    'devices_handle_discards_safely'
+
+
 Version History
 ---------------
 1.0.0	Initial version.  Support for RAID 4/5/6
diff --git a/Documentation/device-mapper/statistics.txt b/Documentation/device-mapper/statistics.txt
index 4919b2dfd1b391c4169de1b66f5e78bd9ba2d9cc..6f5ef944ca4c8fcdbe9ce8cb06b0bddf0bcdfe59 100644
--- a/Documentation/device-mapper/statistics.txt
+++ b/Documentation/device-mapper/statistics.txt
@@ -121,6 +121,10 @@ Messages
 
 	Output format:
 	  <region_id>: <start_sector>+<length> <step> <program_id> <aux_data>
+	        precise_timestamps histogram:n1,n2,n3,...
+
+	The strings "precise_timestamps" and "histogram" are printed only
+	if they were specified when creating the region.
 
     @stats_print <region_id> [<starting_line> <number_of_lines>]
 
diff --git a/drivers/md/dm-cache-policy-smq.c b/drivers/md/dm-cache-policy-smq.c
index 200366c62231dd5f8f38f74284a42810c8603d19..1ffbeb1b3ea6088fd07bed9c68352821223c0b84 100644
--- a/drivers/md/dm-cache-policy-smq.c
+++ b/drivers/md/dm-cache-policy-smq.c
@@ -772,7 +772,7 @@ struct smq_policy {
 	struct dm_cache_policy policy;
 
 	/* protects everything */
-	struct mutex lock;
+	spinlock_t lock;
 	dm_cblock_t cache_size;
 	sector_t cache_block_size;
 
@@ -807,13 +807,7 @@ struct smq_policy {
 	/*
 	 * Keeps track of time, incremented by the core.  We use this to
 	 * avoid attributing multiple hits within the same tick.
-	 *
-	 * Access to tick_protected should be done with the spin lock held.
-	 * It's copied to tick at the start of the map function (within the
-	 * mutex).
 	 */
-	spinlock_t tick_lock;
-	unsigned tick_protected;
 	unsigned tick;
 
 	/*
@@ -1296,46 +1290,20 @@ static void smq_destroy(struct dm_cache_policy *p)
 	kfree(mq);
 }
 
-static void copy_tick(struct smq_policy *mq)
-{
-	unsigned long flags, tick;
-
-	spin_lock_irqsave(&mq->tick_lock, flags);
-	tick = mq->tick_protected;
-	if (tick != mq->tick) {
-		update_sentinels(mq);
-		end_hotspot_period(mq);
-		end_cache_period(mq);
-		mq->tick = tick;
-	}
-	spin_unlock_irqrestore(&mq->tick_lock, flags);
-}
-
-static bool maybe_lock(struct smq_policy *mq, bool can_block)
-{
-	if (can_block) {
-		mutex_lock(&mq->lock);
-		return true;
-	} else
-		return mutex_trylock(&mq->lock);
-}
-
 static int smq_map(struct dm_cache_policy *p, dm_oblock_t oblock,
 		   bool can_block, bool can_migrate, bool fast_promote,
 		   struct bio *bio, struct policy_locker *locker,
 		   struct policy_result *result)
 {
 	int r;
+	unsigned long flags;
 	struct smq_policy *mq = to_smq_policy(p);
 
 	result->op = POLICY_MISS;
 
-	if (!maybe_lock(mq, can_block))
-		return -EWOULDBLOCK;
-
-	copy_tick(mq);
+	spin_lock_irqsave(&mq->lock, flags);
 	r = map(mq, bio, oblock, can_migrate, fast_promote, locker, result);
-	mutex_unlock(&mq->lock);
+	spin_unlock_irqrestore(&mq->lock, flags);
 
 	return r;
 }
@@ -1343,20 +1311,18 @@ static int smq_map(struct dm_cache_policy *p, dm_oblock_t oblock,
 static int smq_lookup(struct dm_cache_policy *p, dm_oblock_t oblock, dm_cblock_t *cblock)
 {
 	int r;
+	unsigned long flags;
 	struct smq_policy *mq = to_smq_policy(p);
 	struct entry *e;
 
-	if (!mutex_trylock(&mq->lock))
-		return -EWOULDBLOCK;
-
+	spin_lock_irqsave(&mq->lock, flags);
 	e = h_lookup(&mq->table, oblock);
 	if (e) {
 		*cblock = infer_cblock(mq, e);
 		r = 0;
 	} else
 		r = -ENOENT;
-
-	mutex_unlock(&mq->lock);
+	spin_unlock_irqrestore(&mq->lock, flags);
 
 	return r;
 }
@@ -1375,20 +1341,22 @@ static void __smq_set_clear_dirty(struct smq_policy *mq, dm_oblock_t oblock, boo
 
 static void smq_set_dirty(struct dm_cache_policy *p, dm_oblock_t oblock)
 {
+	unsigned long flags;
 	struct smq_policy *mq = to_smq_policy(p);
 
-	mutex_lock(&mq->lock);
+	spin_lock_irqsave(&mq->lock, flags);
 	__smq_set_clear_dirty(mq, oblock, true);
-	mutex_unlock(&mq->lock);
+	spin_unlock_irqrestore(&mq->lock, flags);
 }
 
 static void smq_clear_dirty(struct dm_cache_policy *p, dm_oblock_t oblock)
 {
 	struct smq_policy *mq = to_smq_policy(p);
+	unsigned long flags;
 
-	mutex_lock(&mq->lock);
+	spin_lock_irqsave(&mq->lock, flags);
 	__smq_set_clear_dirty(mq, oblock, false);
-	mutex_unlock(&mq->lock);
+	spin_unlock_irqrestore(&mq->lock, flags);
 }
 
 static int smq_load_mapping(struct dm_cache_policy *p,
@@ -1433,14 +1401,14 @@ static int smq_walk_mappings(struct dm_cache_policy *p, policy_walk_fn fn,
 	struct smq_policy *mq = to_smq_policy(p);
 	int r = 0;
 
-	mutex_lock(&mq->lock);
-
+	/*
+	 * We don't need to lock here since this method is only called once
+	 * the IO has stopped.
+	 */
 	r = smq_save_hints(mq, &mq->clean, fn, context);
 	if (!r)
 		r = smq_save_hints(mq, &mq->dirty, fn, context);
 
-	mutex_unlock(&mq->lock);
-
 	return r;
 }
 
@@ -1458,10 +1426,11 @@ static void __remove_mapping(struct smq_policy *mq, dm_oblock_t oblock)
 static void smq_remove_mapping(struct dm_cache_policy *p, dm_oblock_t oblock)
 {
 	struct smq_policy *mq = to_smq_policy(p);
+	unsigned long flags;
 
-	mutex_lock(&mq->lock);
+	spin_lock_irqsave(&mq->lock, flags);
 	__remove_mapping(mq, oblock);
-	mutex_unlock(&mq->lock);
+	spin_unlock_irqrestore(&mq->lock, flags);
 }
 
 static int __remove_cblock(struct smq_policy *mq, dm_cblock_t cblock)
@@ -1480,11 +1449,12 @@ static int __remove_cblock(struct smq_policy *mq, dm_cblock_t cblock)
 static int smq_remove_cblock(struct dm_cache_policy *p, dm_cblock_t cblock)
 {
 	int r;
+	unsigned long flags;
 	struct smq_policy *mq = to_smq_policy(p);
 
-	mutex_lock(&mq->lock);
+	spin_lock_irqsave(&mq->lock, flags);
 	r = __remove_cblock(mq, cblock);
-	mutex_unlock(&mq->lock);
+	spin_unlock_irqrestore(&mq->lock, flags);
 
 	return r;
 }
@@ -1537,11 +1507,12 @@ static int smq_writeback_work(struct dm_cache_policy *p, dm_oblock_t *oblock,
 			      dm_cblock_t *cblock, bool critical_only)
 {
 	int r;
+	unsigned long flags;
 	struct smq_policy *mq = to_smq_policy(p);
 
-	mutex_lock(&mq->lock);
+	spin_lock_irqsave(&mq->lock, flags);
 	r = __smq_writeback_work(mq, oblock, cblock, critical_only);
-	mutex_unlock(&mq->lock);
+	spin_unlock_irqrestore(&mq->lock, flags);
 
 	return r;
 }
@@ -1562,21 +1533,23 @@ static void __force_mapping(struct smq_policy *mq,
 static void smq_force_mapping(struct dm_cache_policy *p,
 			      dm_oblock_t current_oblock, dm_oblock_t new_oblock)
 {
+	unsigned long flags;
 	struct smq_policy *mq = to_smq_policy(p);
 
-	mutex_lock(&mq->lock);
+	spin_lock_irqsave(&mq->lock, flags);
 	__force_mapping(mq, current_oblock, new_oblock);
-	mutex_unlock(&mq->lock);
+	spin_unlock_irqrestore(&mq->lock, flags);
 }
 
 static dm_cblock_t smq_residency(struct dm_cache_policy *p)
 {
 	dm_cblock_t r;
+	unsigned long flags;
 	struct smq_policy *mq = to_smq_policy(p);
 
-	mutex_lock(&mq->lock);
+	spin_lock_irqsave(&mq->lock, flags);
 	r = to_cblock(mq->cache_alloc.nr_allocated);
-	mutex_unlock(&mq->lock);
+	spin_unlock_irqrestore(&mq->lock, flags);
 
 	return r;
 }
@@ -1586,15 +1559,12 @@ static void smq_tick(struct dm_cache_policy *p, bool can_block)
 	struct smq_policy *mq = to_smq_policy(p);
 	unsigned long flags;
 
-	spin_lock_irqsave(&mq->tick_lock, flags);
-	mq->tick_protected++;
-	spin_unlock_irqrestore(&mq->tick_lock, flags);
-
-	if (can_block) {
-		mutex_lock(&mq->lock);
-		copy_tick(mq);
-		mutex_unlock(&mq->lock);
-	}
+	spin_lock_irqsave(&mq->lock, flags);
+	mq->tick++;
+	update_sentinels(mq);
+	end_hotspot_period(mq);
+	end_cache_period(mq);
+	spin_unlock_irqrestore(&mq->lock, flags);
 }
 
 /* Init the policy plugin interface function pointers. */
@@ -1694,10 +1664,8 @@ static struct dm_cache_policy *smq_create(dm_cblock_t cache_size,
 	} else
 		mq->cache_hit_bits = NULL;
 
-	mq->tick_protected = 0;
 	mq->tick = 0;
-	mutex_init(&mq->lock);
-	spin_lock_init(&mq->tick_lock);
+	spin_lock_init(&mq->lock);
 
 	q_init(&mq->hotspot, &mq->es, NR_HOTSPOT_LEVELS);
 	mq->hotspot.nr_top_levels = 8;
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 7245071778dba2f28bac62057f7b2bb444fc56e3..dd90d1236f4a46be1cf28d7ef8ebc5d64235adf7 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -424,7 +424,6 @@ static void free_migration(struct dm_cache_migration *mg)
 		wake_up(&cache->migration_wait);
 
 	mempool_free(mg, cache->migration_pool);
-	wake_worker(cache);
 }
 
 static int prealloc_data_structs(struct cache *cache, struct prealloc *p)
@@ -1064,14 +1063,6 @@ static void dec_io_migrations(struct cache *cache)
 	atomic_dec(&cache->nr_io_migrations);
 }
 
-static void __cell_release(struct cache *cache, struct dm_bio_prison_cell *cell,
-			   bool holder, struct bio_list *bios)
-{
-	(holder ? dm_cell_release : dm_cell_release_no_holder)
-		(cache->prison, cell, bios);
-	free_prison_cell(cache, cell);
-}
-
 static bool discard_or_flush(struct bio *bio)
 {
 	return bio->bi_rw & (REQ_FLUSH | REQ_FUA | REQ_DISCARD);
@@ -1079,14 +1070,13 @@ static bool discard_or_flush(struct bio *bio)
 
 static void __cell_defer(struct cache *cache, struct dm_bio_prison_cell *cell)
 {
-	if (discard_or_flush(cell->holder))
+	if (discard_or_flush(cell->holder)) {
 		/*
-		 * We have to handle these bios
-		 * individually.
+		 * We have to handle these bios individually.
 		 */
-		__cell_release(cache, cell, true, &cache->deferred_bios);
-
-	else
+		dm_cell_release(cache->prison, cell, &cache->deferred_bios);
+		free_prison_cell(cache, cell);
+	} else
 		list_add_tail(&cell->user_list, &cache->deferred_cells);
 }
 
@@ -1113,7 +1103,7 @@ static void cell_defer(struct cache *cache, struct dm_bio_prison_cell *cell, boo
 static void cell_error_with_code(struct cache *cache, struct dm_bio_prison_cell *cell, int err)
 {
 	dm_cell_error(cache->prison, cell, err);
-	dm_bio_prison_free_cell(cache->prison, cell);
+	free_prison_cell(cache, cell);
 }
 
 static void cell_requeue(struct cache *cache, struct dm_bio_prison_cell *cell)
@@ -1123,8 +1113,11 @@ static void cell_requeue(struct cache *cache, struct dm_bio_prison_cell *cell)
 
 static void free_io_migration(struct dm_cache_migration *mg)
 {
-	dec_io_migrations(mg->cache);
+	struct cache *cache = mg->cache;
+
+	dec_io_migrations(cache);
 	free_migration(mg);
+	wake_worker(cache);
 }
 
 static void migration_failure(struct dm_cache_migration *mg)
@@ -1351,16 +1344,18 @@ static void issue_discard(struct dm_cache_migration *mg)
 {
 	dm_dblock_t b, e;
 	struct bio *bio = mg->new_ocell->holder;
+	struct cache *cache = mg->cache;
 
-	calc_discard_block_range(mg->cache, bio, &b, &e);
+	calc_discard_block_range(cache, bio, &b, &e);
 	while (b != e) {
-		set_discard(mg->cache, b);
+		set_discard(cache, b);
 		b = to_dblock(from_dblock(b) + 1);
 	}
 
 	bio_endio(bio);
-	cell_defer(mg->cache, mg->new_ocell, false);
+	cell_defer(cache, mg->new_ocell, false);
 	free_migration(mg);
+	wake_worker(cache);
 }
 
 static void issue_copy_or_discard(struct dm_cache_migration *mg)
@@ -1729,6 +1724,8 @@ static void remap_cell_to_origin_clear_discard(struct cache *cache,
 		remap_to_origin(cache, bio);
 		issue(cache, bio);
 	}
+
+	free_prison_cell(cache, cell);
 }
 
 static void remap_cell_to_cache_dirty(struct cache *cache, struct dm_bio_prison_cell *cell,
@@ -1763,6 +1760,8 @@ static void remap_cell_to_cache_dirty(struct cache *cache, struct dm_bio_prison_
 		remap_to_cache(cache, bio, cblock);
 		issue(cache, bio);
 	}
+
+	free_prison_cell(cache, cell);
 }
 
 /*----------------------------------------------------------------*/
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index ba5c2105f4e62f4d05c755fca131484f7633b6c1..d60c88df5234a0099292712cc1117dc1e65b78e0 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -1811,11 +1811,13 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	}
 	cc->iv_offset = tmpll;
 
-	if (dm_get_device(ti, argv[3], dm_table_get_mode(ti->table), &cc->dev)) {
+	ret = dm_get_device(ti, argv[3], dm_table_get_mode(ti->table), &cc->dev);
+	if (ret) {
 		ti->error = "Device lookup failed";
 		goto bad;
 	}
 
+	ret = -EINVAL;
 	if (sscanf(argv[4], "%llu%c", &tmpll, &dummy) != 1) {
 		ti->error = "Invalid device sector";
 		goto bad;
diff --git a/drivers/md/dm-delay.c b/drivers/md/dm-delay.c
index 57b6a1901c917127eccb8247cd1015a9b588159e..b34f6e27293dcc9e408289c7955af921b4cb8990 100644
--- a/drivers/md/dm-delay.c
+++ b/drivers/md/dm-delay.c
@@ -129,6 +129,7 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	struct delay_c *dc;
 	unsigned long long tmpll;
 	char dummy;
+	int ret;
 
 	if (argc != 3 && argc != 6) {
 		ti->error = "requires exactly 3 or 6 arguments";
@@ -143,6 +144,7 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 
 	dc->reads = dc->writes = 0;
 
+	ret = -EINVAL;
 	if (sscanf(argv[1], "%llu%c", &tmpll, &dummy) != 1) {
 		ti->error = "Invalid device sector";
 		goto bad;
@@ -154,12 +156,14 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 		goto bad;
 	}
 
-	if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
-			  &dc->dev_read)) {
+	ret = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
+			    &dc->dev_read);
+	if (ret) {
 		ti->error = "Device lookup failed";
 		goto bad;
 	}
 
+	ret = -EINVAL;
 	dc->dev_write = NULL;
 	if (argc == 3)
 		goto out;
@@ -175,13 +179,15 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 		goto bad_dev_read;
 	}
 
-	if (dm_get_device(ti, argv[3], dm_table_get_mode(ti->table),
-			  &dc->dev_write)) {
+	ret = dm_get_device(ti, argv[3], dm_table_get_mode(ti->table),
+			    &dc->dev_write);
+	if (ret) {
 		ti->error = "Write device lookup failed";
 		goto bad_dev_read;
 	}
 
 out:
+	ret = -EINVAL;
 	dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
 	if (!dc->kdelayd_wq) {
 		DMERR("Couldn't start kdelayd");
@@ -208,7 +214,7 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	dm_put_device(ti, dc->dev_read);
 bad:
 	kfree(dc);
-	return -EINVAL;
+	return ret;
 }
 
 static void delay_dtr(struct dm_target *ti)
diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c
index afab13bd683e0e7bed2c21846155a0a9ce086e6e..645e8b4f808eee3f1f63e2432bf12cf8cbcde961 100644
--- a/drivers/md/dm-flakey.c
+++ b/drivers/md/dm-flakey.c
@@ -183,6 +183,7 @@ static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 
 	devname = dm_shift_arg(&as);
 
+	r = -EINVAL;
 	if (sscanf(dm_shift_arg(&as), "%llu%c", &tmpll, &dummy) != 1) {
 		ti->error = "Invalid device sector";
 		goto bad;
@@ -211,7 +212,8 @@ static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	if (r)
 		goto bad;
 
-	if (dm_get_device(ti, devname, dm_table_get_mode(ti->table), &fc->dev)) {
+	r = dm_get_device(ti, devname, dm_table_get_mode(ti->table), &fc->dev);
+	if (r) {
 		ti->error = "Device lookup failed";
 		goto bad;
 	}
@@ -224,7 +226,7 @@ static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 
 bad:
 	kfree(fc);
-	return -EINVAL;
+	return r;
 }
 
 static void flakey_dtr(struct dm_target *ti)
diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
index 7dd5fc8e3eeaac8d8d8f148862ecf3c6f298fec2..436f5c9b6aea56dd6652696cc3eac489690c1e8e 100644
--- a/drivers/md/dm-linear.c
+++ b/drivers/md/dm-linear.c
@@ -30,6 +30,7 @@ static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	struct linear_c *lc;
 	unsigned long long tmp;
 	char dummy;
+	int ret;
 
 	if (argc != 2) {
 		ti->error = "Invalid argument count";
@@ -42,13 +43,15 @@ static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 		return -ENOMEM;
 	}
 
+	ret = -EINVAL;
 	if (sscanf(argv[1], "%llu%c", &tmp, &dummy) != 1) {
 		ti->error = "dm-linear: Invalid device sector";
 		goto bad;
 	}
 	lc->start = tmp;
 
-	if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &lc->dev)) {
+	ret = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &lc->dev);
+	if (ret) {
 		ti->error = "dm-linear: Device lookup failed";
 		goto bad;
 	}
@@ -61,7 +64,7 @@ static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 
       bad:
 	kfree(lc);
-	return -EINVAL;
+	return ret;
 }
 
 static void linear_dtr(struct dm_target *ti)
diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c
index 316cc3fb741f972a075fb56888585ef4ada72468..b2912dbac8bce7356f06eebc8063317c6bc411b0 100644
--- a/drivers/md/dm-log-writes.c
+++ b/drivers/md/dm-log-writes.c
@@ -417,6 +417,7 @@ static int log_writes_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	struct log_writes_c *lc;
 	struct dm_arg_set as;
 	const char *devname, *logdevname;
+	int ret;
 
 	as.argc = argc;
 	as.argv = argv;
@@ -440,18 +441,22 @@ static int log_writes_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	atomic_set(&lc->pending_blocks, 0);
 
 	devname = dm_shift_arg(&as);
-	if (dm_get_device(ti, devname, dm_table_get_mode(ti->table), &lc->dev)) {
+	ret = dm_get_device(ti, devname, dm_table_get_mode(ti->table), &lc->dev);
+	if (ret) {
 		ti->error = "Device lookup failed";
 		goto bad;
 	}
 
 	logdevname = dm_shift_arg(&as);
-	if (dm_get_device(ti, logdevname, dm_table_get_mode(ti->table), &lc->logdev)) {
+	ret = dm_get_device(ti, logdevname, dm_table_get_mode(ti->table),
+			    &lc->logdev);
+	if (ret) {
 		ti->error = "Log device lookup failed";
 		dm_put_device(ti, lc->dev);
 		goto bad;
 	}
 
+	ret = -EINVAL;
 	lc->log_kthread = kthread_run(log_writes_kthread, lc, "log-write");
 	if (!lc->log_kthread) {
 		ti->error = "Couldn't alloc kthread";
@@ -476,7 +481,7 @@ static int log_writes_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 
 bad:
 	kfree(lc);
-	return -EINVAL;
+	return ret;
 }
 
 static int log_mark(struct log_writes_c *lc, char *data)
diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index e1eabfb2f52da0bc017f7be80dc7d8d949dfa52e..f2a363a89629902350649cb818f6159ecda1afd9 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -945,16 +945,18 @@ static int get_mirror(struct mirror_set *ms, struct dm_target *ti,
 {
 	unsigned long long offset;
 	char dummy;
+	int ret;
 
 	if (sscanf(argv[1], "%llu%c", &offset, &dummy) != 1) {
 		ti->error = "Invalid offset";
 		return -EINVAL;
 	}
 
-	if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
-			  &ms->mirror[mirror].dev)) {
+	ret = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
+			    &ms->mirror[mirror].dev);
+	if (ret) {
 		ti->error = "Device lookup failure";
-		return -ENXIO;
+		return ret;
 	}
 
 	ms->mirror[mirror].ms = ms;
diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
index 808b8419bc48d42423d750eb64d178bfa77509e5..bf71583296f732b6b78c71ae67dee5222824b2f8 100644
--- a/drivers/md/dm-snap-persistent.c
+++ b/drivers/md/dm-snap-persistent.c
@@ -533,7 +533,7 @@ static int read_exceptions(struct pstore *ps,
 		chunk = area_location(ps, ps->current_area);
 
 		area = dm_bufio_read(client, chunk, &bp);
-		if (unlikely(IS_ERR(area))) {
+		if (IS_ERR(area)) {
 			r = PTR_ERR(area);
 			goto ret_destroy_bufio;
 		}
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index d10b6876018eee6b62ca7f937022d3648c6295c0..c0bcd6516dfe17f8e7a06ec8c66d1e1d5801f133 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -63,6 +63,13 @@ struct dm_snapshot {
 	 */
 	int valid;
 
+	/*
+	 * The snapshot overflowed because of a write to the snapshot device.
+	 * We don't have to invalidate the snapshot in this case, but we need
+	 * to prevent further writes.
+	 */
+	int snapshot_overflowed;
+
 	/* Origin writes don't trigger exceptions until this is set */
 	int active;
 
@@ -1152,6 +1159,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 
 	s->ti = ti;
 	s->valid = 1;
+	s->snapshot_overflowed = 0;
 	s->active = 0;
 	atomic_set(&s->pending_exceptions_count, 0);
 	s->exception_start_sequence = 0;
@@ -1301,6 +1309,7 @@ static void __handover_exceptions(struct dm_snapshot *snap_src,
 
 	snap_dest->ti->max_io_len = snap_dest->store->chunk_size;
 	snap_dest->valid = snap_src->valid;
+	snap_dest->snapshot_overflowed = snap_src->snapshot_overflowed;
 
 	/*
 	 * Set source invalid to ensure it receives no further I/O.
@@ -1691,7 +1700,7 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio)
 	 * to copy an exception */
 	down_write(&s->lock);
 
-	if (!s->valid) {
+	if (!s->valid || (unlikely(s->snapshot_overflowed) && bio_rw(bio) == WRITE)) {
 		r = -EIO;
 		goto out_unlock;
 	}
@@ -1715,7 +1724,7 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio)
 			pe = alloc_pending_exception(s);
 			down_write(&s->lock);
 
-			if (!s->valid) {
+			if (!s->valid || s->snapshot_overflowed) {
 				free_pending_exception(pe);
 				r = -EIO;
 				goto out_unlock;
@@ -1730,7 +1739,8 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio)
 
 			pe = __find_pending_exception(s, pe, chunk);
 			if (!pe) {
-				__invalidate_snapshot(s, -ENOMEM);
+				s->snapshot_overflowed = 1;
+				DMERR("Snapshot overflowed: Unable to allocate exception.");
 				r = -EIO;
 				goto out_unlock;
 			}
@@ -1990,6 +2000,8 @@ static void snapshot_status(struct dm_target *ti, status_type_t type,
 			DMEMIT("Invalid");
 		else if (snap->merge_failed)
 			DMEMIT("Merge failed");
+		else if (snap->snapshot_overflowed)
+			DMEMIT("Overflow");
 		else {
 			if (snap->store->type->usage) {
 				sector_t total_sectors, sectors_allocated,
@@ -2353,7 +2365,7 @@ static struct target_type origin_target = {
 
 static struct target_type snapshot_target = {
 	.name    = "snapshot",
-	.version = {1, 13, 0},
+	.version = {1, 14, 0},
 	.module  = THIS_MODULE,
 	.ctr     = snapshot_ctr,
 	.dtr     = snapshot_dtr,
diff --git a/drivers/md/dm-stats.c b/drivers/md/dm-stats.c
index 8a8b48fa901ab162696d89c94679d78bff6f7d9c..8289804ccd998a1d4d9be9fce2a32bd4bfa6cad8 100644
--- a/drivers/md/dm-stats.c
+++ b/drivers/md/dm-stats.c
@@ -457,12 +457,24 @@ static int dm_stats_list(struct dm_stats *stats, const char *program,
 	list_for_each_entry(s, &stats->list, list_entry) {
 		if (!program || !strcmp(program, s->program_id)) {
 			len = s->end - s->start;
-			DMEMIT("%d: %llu+%llu %llu %s %s\n", s->id,
+			DMEMIT("%d: %llu+%llu %llu %s %s", s->id,
 				(unsigned long long)s->start,
 				(unsigned long long)len,
 				(unsigned long long)s->step,
 				s->program_id,
 				s->aux_data);
+			if (s->stat_flags & STAT_PRECISE_TIMESTAMPS)
+				DMEMIT(" precise_timestamps");
+			if (s->n_histogram_entries) {
+				unsigned i;
+				DMEMIT(" histogram:");
+				for (i = 0; i < s->n_histogram_entries; i++) {
+					if (i)
+						DMEMIT(",");
+					DMEMIT("%llu", s->histogram_boundaries[i]);
+				}
+			}
+			DMEMIT("\n");
 		}
 	}
 	mutex_unlock(&stats->mutex);
diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
index 484029db8cba10931a91b0fabfdd58c315904a9d..797ddb900b062079cae7aca92b0b7bad2ead619f 100644
--- a/drivers/md/dm-stripe.c
+++ b/drivers/md/dm-stripe.c
@@ -75,13 +75,15 @@ static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
 {
 	unsigned long long start;
 	char dummy;
+	int ret;
 
 	if (sscanf(argv[1], "%llu%c", &start, &dummy) != 1)
 		return -EINVAL;
 
-	if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
-			  &sc->stripe[stripe].dev))
-		return -ENXIO;
+	ret = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
+			    &sc->stripe[stripe].dev);
+	if (ret)
+		return ret;
 
 	sc->stripe[stripe].physical_start = start;
 
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 271a6624936313863a753aa6ddde802a41bc27be..6578b7bc1fbba5339a740c8447f8bfdf8266fd8f 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -332,9 +332,6 @@ struct thin_c {
  *
  * Description:
  *    Asynchronously issue a discard request for the sectors in question.
- *    NOTE: this variant of blk-core's blkdev_issue_discard() is a stop-gap
- *    that is being kept local to DM thinp until the block changes to allow
- *    late bio splitting land upstream.
  */
 static int __blkdev_issue_discard_async(struct block_device *bdev, sector_t sector,
 					sector_t nr_sects, gfp_t gfp_mask, unsigned long flags,
@@ -342,91 +339,36 @@ static int __blkdev_issue_discard_async(struct block_device *bdev, sector_t sect
 {
 	struct request_queue *q = bdev_get_queue(bdev);
 	int type = REQ_WRITE | REQ_DISCARD;
-	unsigned int max_discard_sectors, granularity;
-	int alignment;
 	struct bio *bio;
-	int ret = 0;
-	struct blk_plug plug;
 
-	if (!q)
+	if (!q || !nr_sects)
 		return -ENXIO;
 
 	if (!blk_queue_discard(q))
 		return -EOPNOTSUPP;
 
-	/* Zero-sector (unknown) and one-sector granularities are the same.  */
-	granularity = max(q->limits.discard_granularity >> 9, 1U);
-	alignment = (bdev_discard_alignment(bdev) >> 9) % granularity;
-
-	/*
-	 * Ensure that max_discard_sectors is of the proper
-	 * granularity, so that requests stay aligned after a split.
-	 */
-	max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
-	max_discard_sectors -= max_discard_sectors % granularity;
-	if (unlikely(!max_discard_sectors)) {
-		/* Avoid infinite loop below. Being cautious never hurts. */
-		return -EOPNOTSUPP;
-	}
-
 	if (flags & BLKDEV_DISCARD_SECURE) {
 		if (!blk_queue_secdiscard(q))
 			return -EOPNOTSUPP;
 		type |= REQ_SECURE;
 	}
 
-	blk_start_plug(&plug);
-	while (nr_sects) {
-		unsigned int req_sects;
-		sector_t end_sect, tmp;
-
-		/*
-		 * Required bio_put occurs in bio_endio thanks to bio_chain below
-		 */
-		bio = bio_alloc(gfp_mask, 1);
-		if (!bio) {
-			ret = -ENOMEM;
-			break;
-		}
-
-		req_sects = min_t(sector_t, nr_sects, max_discard_sectors);
-
-		/*
-		 * If splitting a request, and the next starting sector would be
-		 * misaligned, stop the discard at the previous aligned sector.
-		 */
-		end_sect = sector + req_sects;
-		tmp = end_sect;
-		if (req_sects < nr_sects &&
-		    sector_div(tmp, granularity) != alignment) {
-			end_sect = end_sect - alignment;
-			sector_div(end_sect, granularity);
-			end_sect = end_sect * granularity + alignment;
-			req_sects = end_sect - sector;
-		}
-
-		bio_chain(bio, parent_bio);
-
-		bio->bi_iter.bi_sector = sector;
-		bio->bi_bdev = bdev;
+	/*
+	 * Required bio_put occurs in bio_endio thanks to bio_chain below
+	 */
+	bio = bio_alloc(gfp_mask, 1);
+	if (!bio)
+		return -ENOMEM;
 
-		bio->bi_iter.bi_size = req_sects << 9;
-		nr_sects -= req_sects;
-		sector = end_sect;
+	bio_chain(bio, parent_bio);
 
-		submit_bio(type, bio);
+	bio->bi_iter.bi_sector = sector;
+	bio->bi_bdev = bdev;
+	bio->bi_iter.bi_size = nr_sects << 9;
 
-		/*
-		 * We can loop for a long time in here, if someone does
-		 * full device discards (like mkfs). Be nice and allow
-		 * us to schedule out to avoid softlocking if preempt
-		 * is disabled.
-		 */
-		cond_resched();
-	}
-	blk_finish_plug(&plug);
+	submit_bio(type, bio);
 
-	return ret;
+	return 0;
 }
 
 static bool block_size_is_power_of_two(struct pool *pool)
@@ -1543,9 +1485,8 @@ static void process_discard_cell_no_passdown(struct thin_c *tc,
 }
 
 /*
- * FIXME: DM local hack to defer parent bios's end_io until we
- * _know_ all chained sub range discard bios have completed.
- * Will go away once late bio splitting lands upstream!
+ * __bio_inc_remaining() is used to defer parent bios's end_io until
+ * we _know_ all chained sub range discard bios have completed.
  */
 static inline void __bio_inc_remaining(struct bio *bio)
 {
diff --git a/drivers/md/dm-verity.c b/drivers/md/dm-verity.c
index c137dcb147b8329015ff1872f09418993eab6df4..edc624bccf9aa841dc76073208735bd2455e12a8 100644
--- a/drivers/md/dm-verity.c
+++ b/drivers/md/dm-verity.c
@@ -26,8 +26,6 @@
 #define DM_VERITY_ENV_LENGTH		42
 #define DM_VERITY_ENV_VAR_NAME		"DM_VERITY_ERR_BLOCK_NR"
 
-#define DM_VERITY_IO_VEC_INLINE		16
-#define DM_VERITY_MEMPOOL_SIZE		4
 #define DM_VERITY_DEFAULT_PREFETCH_SIZE	262144
 
 #define DM_VERITY_MAX_LEVELS		63
@@ -76,8 +74,6 @@ struct dm_verity {
 	enum verity_mode mode;	/* mode for handling verification errors */
 	unsigned corrupted_errs;/* Number of errors for corrupted blocks */
 
-	mempool_t *vec_mempool;	/* mempool of bio vector */
-
 	struct workqueue_struct *verify_wq;
 
 	/* starting blocks for each tree level. 0 is the lowest level. */
@@ -271,7 +267,7 @@ static int verity_verify_level(struct dm_verity_io *io, sector_t block,
 	verity_hash_at_level(v, block, level, &hash_block, &offset);
 
 	data = dm_bufio_read(v->bufio, hash_block, &buf);
-	if (unlikely(IS_ERR(data)))
+	if (IS_ERR(data))
 		return PTR_ERR(data);
 
 	aux = dm_bufio_get_aux_data(buf);
@@ -677,9 +673,6 @@ static void verity_dtr(struct dm_target *ti)
 	if (v->verify_wq)
 		destroy_workqueue(v->verify_wq);
 
-	if (v->vec_mempool)
-		mempool_destroy(v->vec_mempool);
-
 	if (v->bufio)
 		dm_bufio_client_destroy(v->bufio);
 
@@ -948,14 +941,6 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 
 	ti->per_bio_data_size = roundup(sizeof(struct dm_verity_io) + v->shash_descsize + v->digest_size * 2, __alignof__(struct dm_verity_io));
 
-	v->vec_mempool = mempool_create_kmalloc_pool(DM_VERITY_MEMPOOL_SIZE,
-					BIO_MAX_PAGES * sizeof(struct bio_vec));
-	if (!v->vec_mempool) {
-		ti->error = "Cannot allocate vector mempool";
-		r = -ENOMEM;
-		goto bad;
-	}
-
 	/* WQ_UNBOUND greatly improves performance when running on ramdisk */
 	v->verify_wq = alloc_workqueue("kverityd", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | WQ_UNBOUND, num_online_cpus());
 	if (!v->verify_wq) {
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 6ffc01bb85f2a8ee6a127cf3c651bebd3cdf6a32..6264781dc69a6066b88d719537c471b7d1cd7b27 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1464,7 +1464,7 @@ static void __map_bio(struct dm_target_io *tio)
 		md = tio->io->md;
 		dec_pending(tio->io, r);
 		free_tio(md, tio);
-	} else if (r) {
+	} else if (r != DM_MAPIO_SUBMITTED) {
 		DMWARN("unimplemented target map return value: %d", r);
 		BUG();
 	}
diff --git a/drivers/md/persistent-data/dm-block-manager.c b/drivers/md/persistent-data/dm-block-manager.c
index 4d6c9b689eaa73d4fccbe44991fc04913e413a8c..88dbe7b97c2c3ca7ace7cbee4b75f80496a0c62a 100644
--- a/drivers/md/persistent-data/dm-block-manager.c
+++ b/drivers/md/persistent-data/dm-block-manager.c
@@ -454,7 +454,7 @@ int dm_bm_read_lock(struct dm_block_manager *bm, dm_block_t b,
 	int r;
 
 	p = dm_bufio_read(bm->bufio, b, (struct dm_buffer **) result);
-	if (unlikely(IS_ERR(p)))
+	if (IS_ERR(p))
 		return PTR_ERR(p);
 
 	aux = dm_bufio_get_aux_data(to_buffer(*result));
@@ -490,7 +490,7 @@ int dm_bm_write_lock(struct dm_block_manager *bm,
 		return -EPERM;
 
 	p = dm_bufio_read(bm->bufio, b, (struct dm_buffer **) result);
-	if (unlikely(IS_ERR(p)))
+	if (IS_ERR(p))
 		return PTR_ERR(p);
 
 	aux = dm_bufio_get_aux_data(to_buffer(*result));
@@ -523,7 +523,7 @@ int dm_bm_read_try_lock(struct dm_block_manager *bm,
 	int r;
 
 	p = dm_bufio_get(bm->bufio, b, (struct dm_buffer **) result);
-	if (unlikely(IS_ERR(p)))
+	if (IS_ERR(p))
 		return PTR_ERR(p);
 	if (unlikely(!p))
 		return -EWOULDBLOCK;
@@ -559,7 +559,7 @@ int dm_bm_write_lock_zero(struct dm_block_manager *bm,
 		return -EPERM;
 
 	p = dm_bufio_new(bm->bufio, b, (struct dm_buffer **) result);
-	if (unlikely(IS_ERR(p)))
+	if (IS_ERR(p))
 		return PTR_ERR(p);
 
 	memset(p, 0, dm_bm_block_size(bm));
diff --git a/drivers/md/persistent-data/dm-btree-remove.c b/drivers/md/persistent-data/dm-btree-remove.c
index 4222f774cf369b1eb1b031bd652854c573b224af..421a36c593e3e7dedef785a5f78c12914c13d8b3 100644
--- a/drivers/md/persistent-data/dm-btree-remove.c
+++ b/drivers/md/persistent-data/dm-btree-remove.c
@@ -409,29 +409,11 @@ static int rebalance3(struct shadow_spine *s, struct dm_btree_info *info,
 	return 0;
 }
 
-static int get_nr_entries(struct dm_transaction_manager *tm,
-			  dm_block_t b, uint32_t *result)
-{
-	int r;
-	struct dm_block *block;
-	struct btree_node *n;
-
-	r = dm_tm_read_lock(tm, b, &btree_node_validator, &block);
-	if (r)
-		return r;
-
-	n = dm_block_data(block);
-	*result = le32_to_cpu(n->header.nr_entries);
-
-	return dm_tm_unlock(tm, block);
-}
-
 static int rebalance_children(struct shadow_spine *s,
 			      struct dm_btree_info *info,
 			      struct dm_btree_value_type *vt, uint64_t key)
 {
 	int i, r, has_left_sibling, has_right_sibling;
-	uint32_t child_entries;
 	struct btree_node *n;
 
 	n = dm_block_data(shadow_current(s));
@@ -458,10 +440,6 @@ static int rebalance_children(struct shadow_spine *s,
 	if (i < 0)
 		return -ENODATA;
 
-	r = get_nr_entries(info->tm, value64(n, i), &child_entries);
-	if (r)
-		return r;
-
 	has_left_sibling = i > 0;
 	has_right_sibling = i < (le32_to_cpu(n->header.nr_entries) - 1);
 
diff --git a/drivers/md/persistent-data/dm-btree.c b/drivers/md/persistent-data/dm-btree.c
index c7726cebc4950c24cb6f6f2b7cacfa6465bddeb6..b6cec258cc2138497b3c8875fc4defdb7523701f 100644
--- a/drivers/md/persistent-data/dm-btree.c
+++ b/drivers/md/persistent-data/dm-btree.c
@@ -420,8 +420,8 @@ EXPORT_SYMBOL_GPL(dm_btree_lookup);
  *
  * Where A* is a shadow of A.
  */
-static int btree_split_sibling(struct shadow_spine *s, dm_block_t root,
-			       unsigned parent_index, uint64_t key)
+static int btree_split_sibling(struct shadow_spine *s, unsigned parent_index,
+			       uint64_t key)
 {
 	int r;
 	size_t size;
@@ -625,7 +625,7 @@ static int btree_insert_raw(struct shadow_spine *s, dm_block_t root,
 			if (top)
 				r = btree_split_beneath(s, key);
 			else
-				r = btree_split_sibling(s, root, i, key);
+				r = btree_split_sibling(s, i, key);
 
 			if (r < 0)
 				return r;
diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h
index 061aca3a962d73a8f9323b6920230d9895a3eb29..d34611e35a30f10995d19cc4ae80aeb4a9547211 100644
--- a/include/uapi/linux/dm-ioctl.h
+++ b/include/uapi/linux/dm-ioctl.h
@@ -267,9 +267,9 @@ enum {
 #define DM_DEV_SET_GEOMETRY	_IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)
 
 #define DM_VERSION_MAJOR	4
-#define DM_VERSION_MINOR	32
+#define DM_VERSION_MINOR	33
 #define DM_VERSION_PATCHLEVEL	0
-#define DM_VERSION_EXTRA	"-ioctl (2015-6-26)"
+#define DM_VERSION_EXTRA	"-ioctl (2015-8-18)"
 
 /* Status bits */
 #define DM_READONLY_FLAG	(1 << 0) /* In/Out */