block: Schedule runtime resume earlier

Instead of scheduling runtime resume of a request queue after a
request has been queued, schedule asynchronous resume during request
allocation. The new pm_request_resume() calls occur after
blk_queue_enter() has increased the q_usage_counter request queue
member. This change is needed for a later patch that will make request
allocation block while the queue status is not RPM_ACTIVE.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Jianchao Wang <jianchao.w.wang@oracle.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-core.c

@@ -956,7 +956,8 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags)
 
 		wait_event(q->mq_freeze_wq,
 			   (atomic_read(&q->mq_freeze_depth) == 0 &&
-			    (pm || !blk_queue_pm_only(q))) ||
+			    (pm || (blk_pm_request_resume(q),
+				    !blk_queue_pm_only(q)))) ||
 			   blk_queue_dying(q));
 		if (blk_queue_dying(q))
 			return -ENODEV;

block/elevator.c

@@ -601,7 +601,6 @@ void __elv_add_request(struct request_queue *q, struct request *rq, int where)
 	trace_block_rq_insert(q, rq);
 
 	blk_pm_add_request(q, rq);
-	blk_pm_request_resume(q);
 
 	rq->q = q;