diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 1bf4a71919ec..9380be7b1895 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -2488,6 +2488,7 @@ static int cache_map(struct dm_target *ti, struct bio *bio)
 
 		} else {
 			inc_hit_counter(cache, bio);
+			pb->all_io_entry = dm_deferred_entry_inc(cache->all_io_ds);
 
 			if (bio_data_dir(bio) == WRITE && writethrough_mode(&cache->features) &&
 			    !is_dirty(cache, lookup_result.cblock))
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 53728be84dee..13abade76ad9 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -232,6 +232,13 @@ struct thin_c {
 	struct bio_list deferred_bio_list;
 	struct bio_list retry_on_resume_list;
 	struct rb_root sort_bio_list; /* sorted list of deferred bios */
+
+	/*
+	 * Ensures the thin is not destroyed until the worker has finished
+	 * iterating the active_thins list.
+	 */
+	atomic_t refcount;
+	struct completion can_destroy;
 };
 
 /*----------------------------------------------------------------*/
@@ -1486,6 +1493,45 @@ static void process_thin_deferred_bios(struct thin_c *tc)
 	blk_finish_plug(&plug);
 }
 
+static void thin_get(struct thin_c *tc);
+static void thin_put(struct thin_c *tc);
+
+/*
+ * We can't hold rcu_read_lock() around code that can block.  So we
+ * find a thin with the rcu lock held; bump a refcount; then drop
+ * the lock.
+ */
+static struct thin_c *get_first_thin(struct pool *pool)
+{
+	struct thin_c *tc = NULL;
+
+	rcu_read_lock();
+	if (!list_empty(&pool->active_thins)) {
+		tc = list_entry_rcu(pool->active_thins.next, struct thin_c, list);
+		thin_get(tc);
+	}
+	rcu_read_unlock();
+
+	return tc;
+}
+
+static struct thin_c *get_next_thin(struct pool *pool, struct thin_c *tc)
+{
+	struct thin_c *old_tc = tc;
+
+	rcu_read_lock();
+	list_for_each_entry_continue_rcu(tc, &pool->active_thins, list) {
+		thin_get(tc);
+		thin_put(old_tc);
+		rcu_read_unlock();
+		return tc;
+	}
+	thin_put(old_tc);
+	rcu_read_unlock();
+
+	return NULL;
+}
+
 static void process_deferred_bios(struct pool *pool)
 {
 	unsigned long flags;
@@ -1493,10 +1539,11 @@ static void process_deferred_bios(struct pool *pool)
 	struct bio_list bios;
 	struct thin_c *tc;
 
-	rcu_read_lock();
-	list_for_each_entry_rcu(tc, &pool->active_thins, list)
+	tc = get_first_thin(pool);
+	while (tc) {
 		process_thin_deferred_bios(tc);
-	rcu_read_unlock();
+		tc = get_next_thin(pool, tc);
+	}
 
 	/*
 	 * If there are any deferred flush bios, we must commit
@@ -1578,7 +1625,7 @@ static void noflush_work(struct thin_c *tc, void (*fn)(struct work_struct *))
 {
 	struct noflush_work w;
 
-	INIT_WORK(&w.worker, fn);
+	INIT_WORK_ONSTACK(&w.worker, fn);
 	w.tc = tc;
 	atomic_set(&w.complete, 0);
 	init_waitqueue_head(&w.wait);
@@ -3061,11 +3108,25 @@ static struct target_type pool_target = {
 /*----------------------------------------------------------------
  * Thin target methods
  *--------------------------------------------------------------*/
+static void thin_get(struct thin_c *tc)
+{
+	atomic_inc(&tc->refcount);
+}
+
+static void thin_put(struct thin_c *tc)
+{
+	if (atomic_dec_and_test(&tc->refcount))
+		complete(&tc->can_destroy);
+}
+
 static void thin_dtr(struct dm_target *ti)
 {
 	struct thin_c *tc = ti->private;
 	unsigned long flags;
 
+	thin_put(tc);
+	wait_for_completion(&tc->can_destroy);
+
 	spin_lock_irqsave(&tc->pool->lock, flags);
 	list_del_rcu(&tc->list);
 	spin_unlock_irqrestore(&tc->pool->lock, flags);
@@ -3101,6 +3162,7 @@ static int thin_ctr(struct dm_target *ti, unsigned argc, char **argv)
 	struct thin_c *tc;
 	struct dm_dev *pool_dev, *origin_dev;
 	struct mapped_device *pool_md;
+	unsigned long flags;
 
 	mutex_lock(&dm_thin_pool_table.mutex);
 
@@ -3191,9 +3253,12 @@ static int thin_ctr(struct dm_target *ti, unsigned argc, char **argv)
 
 	mutex_unlock(&dm_thin_pool_table.mutex);
 
-	spin_lock(&tc->pool->lock);
+	atomic_set(&tc->refcount, 1);
+	init_completion(&tc->can_destroy);
+
+	spin_lock_irqsave(&tc->pool->lock, flags);
 	list_add_tail_rcu(&tc->list, &tc->pool->active_thins);
-	spin_unlock(&tc->pool->lock);
+	spin_unlock_irqrestore(&tc->pool->lock, flags);
 	/*
 	 * This synchronize_rcu() call is needed here otherwise we risk a
 	 * wake_worker() call finding no bios to process (because the newly
diff --git a/drivers/md/dm-verity.c b/drivers/md/dm-verity.c
index 796007a5e0e1..7a7bab8947ae 100644
--- a/drivers/md/dm-verity.c
+++ b/drivers/md/dm-verity.c
@@ -330,15 +330,17 @@ test_block_hash:
 				return r;
 			}
 		}
-
 		todo = 1 << v->data_dev_block_bits;
-		while (io->iter.bi_size) {
+		do {
 			u8 *page;
+			unsigned len;
 			struct bio_vec bv = bio_iter_iovec(bio, io->iter);
 
 			page = kmap_atomic(bv.bv_page);
-			r = crypto_shash_update(desc, page + bv.bv_offset,
-						bv.bv_len);
+			len = bv.bv_len;
+			if (likely(len >= todo))
+				len = todo;
+			r = crypto_shash_update(desc, page + bv.bv_offset, len);
 			kunmap_atomic(page);
 
 			if (r < 0) {
@@ -346,8 +348,9 @@ test_block_hash:
 				return r;
 			}
 
-			bio_advance_iter(bio, &io->iter, bv.bv_len);
-		}
+			bio_advance_iter(bio, &io->iter, len);
+			todo -= len;
+		} while (todo);
 
 		if (!v->version) {
 			r = crypto_shash_update(desc, v->salt, v->salt_size);