diff --git a/block/blk-mq.c b/block/blk-mq.c
index 6418c2a7cd2c..5fca78778c31 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -4354,7 +4354,7 @@ static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,
 {
 	unsigned int i;
 
-	mutex_lock(&set->tag_list_lock);
+	lockdep_assert_held(&set->tag_list_lock);
 
 	/*
 	 * Check to see if we're transitioning to shared (from 1 to 2 queues).
@@ -4379,8 +4379,6 @@ static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,
 			blk_mq_quiesce_queue_nowait(q);
 	}
 	spin_unlock(&set->quiesce_lock);
-
-	mutex_unlock(&set->tag_list_lock);
 }
 
 /* All allocations will be freed in release handler of q->mq_kobj */
@@ -4657,6 +4655,8 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
 int blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
 		struct request_queue *q)
 {
+	unsigned int memflags;
+
 	/* mark the queue as mq asap */
 	q->mq_ops = set->ops;
 
@@ -4675,6 +4675,16 @@ int blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
 	INIT_LIST_HEAD(&q->unused_hctx_list);
 	spin_lock_init(&q->unused_hctx_lock);
 
+	/*
+	 * Keep blk_mq_update_nr_hw_queues() away until the queue is on
+	 * set->tag_list: it changes the number of hardware queues, the tags and
+	 * the maps, and blk_mq_map_swqueue() allocates and frees tags of the set.
+	 * An update can be part of the error handling of a driver, so it must
+	 * not have to wait for somebody who waits for I/O.
+	 */
+	memflags = memalloc_noio_save();
+	mutex_lock(&set->tag_list_lock);
+
 	blk_mq_realloc_hw_ctxs(set, q);
 	if (!q->nr_hw_queues)
 		goto err_hctxs;
@@ -4695,9 +4705,14 @@ int blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
 	blk_mq_init_cpu_queues(q, set->nr_hw_queues);
 	blk_mq_map_swqueue(q);
 	blk_mq_add_queue_tag_set(set, q);
+
+	mutex_unlock(&set->tag_list_lock);
+	memalloc_noio_restore(memflags);
 	return 0;
 
 err_hctxs:
+	mutex_unlock(&set->tag_list_lock);
+	memalloc_noio_restore(memflags);
 	blk_mq_release(q);
 err_exit:
 	q->mq_ops = NULL;