block: don't call blk_mq_quiesce_queue() after queue is frozen

After queue is frozen, no request in this queue can be in use at all, so
there can't be any .queue_rq() running on this queue.  It isn't
necessary to call blk_mq_quiesce_queue() any more, so remove it in both
elevator_switch_mq() and blk_mq_update_nr_requests().

Cc: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>

Fixed up the description a bit.

Signed-off-by: Jens Axboe <axboe@fb.com>

block/blk-mq.c

@@ -2609,7 +2609,6 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
 		return -EINVAL;
 
 	blk_mq_freeze_queue(q);
-	blk_mq_quiesce_queue(q);
 
 	ret = 0;
 	queue_for_each_hw_ctx(q, hctx, i) {
@@ -2635,7 +2634,6 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
 		q->nr_requests = nr;
 
 	blk_mq_unfreeze_queue(q);
-	blk_mq_start_stopped_hw_queues(q, true);
 
 	return ret;
 }

block/elevator.c

@@ -950,7 +950,6 @@ static int elevator_switch_mq(struct request_queue *q,
 	int ret;
 
 	blk_mq_freeze_queue(q);
-	blk_mq_quiesce_queue(q);
 
 	if (q->elevator) {
 		if (q->elevator->registered)
@@ -978,9 +977,7 @@ static int elevator_switch_mq(struct request_queue *q,
 
 out:
 	blk_mq_unfreeze_queue(q);
-	blk_mq_start_stopped_hw_queues(q, true);
 	return ret;
-
 }
 
 /*