Updated from Linux LTS 3.10.21 to 3.10.22

drivers/md/dm-cache-target.c

@@ -151,6 +151,9 @@ struct cache {
 	atomic_t nr_migrations;
 	wait_queue_head_t migration_wait;
 
+	wait_queue_head_t quiescing_wait;
+	atomic_t quiescing_ack;
+
 	/*
 	 * cache_size entries, dirty if set
 	 */
@@ -742,8 +745,9 @@ static void cell_defer(struct cache *cache, struct dm_bio_prison_cell *cell,
 
 static void cleanup_migration(struct dm_cache_migration *mg)
 {
-	dec_nr_migrations(mg->cache);
+	struct cache *cache = mg->cache;
 	free_migration(mg);
+	dec_nr_migrations(cache);
 }
 
 static void migration_failure(struct dm_cache_migration *mg)
@@ -1340,24 +1344,6 @@ static void writeback_some_dirty_blocks(struct cache *cache)
 /*----------------------------------------------------------------
  * Main worker loop
  *--------------------------------------------------------------*/
-static void start_quiescing(struct cache *cache)
-{
-	unsigned long flags;
-
-	spin_lock_irqsave(&cache->lock, flags);
-	cache->quiescing = 1;
-	spin_unlock_irqrestore(&cache->lock, flags);
-}
-
-static void stop_quiescing(struct cache *cache)
-{
-	unsigned long flags;
-
-	spin_lock_irqsave(&cache->lock, flags);
-	cache->quiescing = 0;
-	spin_unlock_irqrestore(&cache->lock, flags);
-}
-
 static bool is_quiescing(struct cache *cache)
 {
 	int r;
@@ -1370,6 +1356,41 @@ static bool is_quiescing(struct cache *cache)
 	return r;
 }
 
+static void ack_quiescing(struct cache *cache)
+{
+	if (is_quiescing(cache)) {
+		atomic_inc(&cache->quiescing_ack);
+		wake_up(&cache->quiescing_wait);
+	}
+}
+
+static void wait_for_quiescing_ack(struct cache *cache)
+{
+	wait_event(cache->quiescing_wait, atomic_read(&cache->quiescing_ack));
+}
+
+static void start_quiescing(struct cache *cache)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&cache->lock, flags);
+	cache->quiescing = true;
+	spin_unlock_irqrestore(&cache->lock, flags);
+
+	wait_for_quiescing_ack(cache);
+}
+
+static void stop_quiescing(struct cache *cache)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&cache->lock, flags);
+	cache->quiescing = false;
+	spin_unlock_irqrestore(&cache->lock, flags);
+
+	atomic_set(&cache->quiescing_ack, 0);
+}
+
 static void wait_for_migrations(struct cache *cache)
 {
 	wait_event(cache->migration_wait, !atomic_read(&cache->nr_migrations));
@@ -1414,16 +1435,15 @@ static void do_worker(struct work_struct *ws)
 	struct cache *cache = container_of(ws, struct cache, worker);
 
 	do {
-		if (!is_quiescing(cache))
+		if (!is_quiescing(cache)) {
+			writeback_some_dirty_blocks(cache);
+			process_deferred_writethrough_bios(cache);
 			process_deferred_bios(cache);
+		}
 
 		process_migrations(cache, &cache->quiesced_migrations, issue_copy);
 		process_migrations(cache, &cache->completed_migrations, complete_migration);
 
-		writeback_some_dirty_blocks(cache);
-
-		process_deferred_writethrough_bios(cache);
-
 		if (commit_if_needed(cache)) {
 			process_deferred_flush_bios(cache, false);
 
@@ -1436,6 +1456,9 @@ static void do_worker(struct work_struct *ws)
 			process_migrations(cache, &cache->need_commit_migrations,
 					   migration_success_post_commit);
 		}
+
+		ack_quiescing(cache);
+
 	} while (more_work(cache));
 }
 
@@ -1998,6 +2021,9 @@ static int cache_create(struct cache_args *ca, struct cache **result)
 	atomic_set(&cache->nr_migrations, 0);
 	init_waitqueue_head(&cache->migration_wait);
 
+	init_waitqueue_head(&cache->quiescing_wait);
+	atomic_set(&cache->quiescing_ack, 0);
+
 	r = -ENOMEM;
 	cache->nr_dirty = 0;
 	cache->dirty_bitset = alloc_bitset(from_cblock(cache->cache_size));