Commit 621739b0 authored Jul 08, 2015 by Mike Snitzer

Revert "dm: only run the queue on completion if congested or no requests pending"

This reverts commit 9a0e609e.
(Resolved a conflict during revert due to commit bfebd1cd that came
after)

This revert is motivated by a couple failure reports on request-based DM
multipath testbeds:
1) Netapp reported that their multipath fault injection test under heavy
   IO load can stall longer than 300 seconds.
2) IBM reported elevated lock contention in their testbed (likely due to
   increased back pressure due to IO not being dispatched as quickly):
   https://www.redhat.com/archives/dm-devel/2015-July/msg00057.html



Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 4.1+

parent 1c751879

drivers/md/dm.c

+2 −6

Original line number	Diff line number	Diff line
		@@ -1067,13 +1067,10 @@ static void rq_end_stats(struct mapped_device md, struct request orig)
		*/
		static void rq_completed(struct mapped_device *md, int rw, bool run_queue)
		{
		int nr_requests_pending;

		atomic_dec(&md->pending[rw]);

		/* nudge anyone waiting on suspend queue */
		nr_requests_pending = md_in_flight(md);
		if (!nr_requests_pending)
		if (!md_in_flight(md))
		wake_up(&md->wait);

		/*
		@@ -1085,8 +1082,7 @@ static void rq_completed(struct mapped_device *md, int rw, bool run_queue)
		if (run_queue) {
		if (md->queue->mq_ops)
		blk_mq_run_hw_queues(md->queue, true);
		else if (!nr_requests_pending \|\|
		(nr_requests_pending >= md->queue->nr_congestion_on))
		else
		blk_run_queue_async(md->queue);
		}