Commit 05a4fed6 authored Jul 07, 2020 by Ming Lei Committed by Jens Axboe Jul 07, 2020

blk-mq: consider non-idle request as "inflight" in blk_mq_rq_inflight()



dm-multipath is the only user of blk_mq_queue_inflight().  When
dm-multipath calls blk_mq_queue_inflight() to check if it has
outstanding IO it can get a false negative.  The reason for this is
blk_mq_rq_inflight() doesn't consider requests that are no longer
MQ_RQ_IN_FLIGHT but that are now MQ_RQ_COMPLETE (->complete isn't
called or finished yet) as "inflight".

This causes request-based dm-multipath's dm_wait_for_completion() to
return before all outstanding dm-multipath requests have actually
completed.  This breaks DM multipath's suspend functionality because
blk-mq requests complete after DM's suspend has finished -- which
shouldn't happen.

Fix this by considering any request not in the MQ_RQ_IDLE state
(so either MQ_RQ_COMPLETE or MQ_RQ_IN_FLIGHT) as "inflight" in
blk_mq_rq_inflight().

Fixes: 3c94d83c ("blk-mq: change blk_mq_queue_busy() to blk_mq_queue_inflight()")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 65752aef

block/blk-mq.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -828,10 +828,10 @@ static bool blk_mq_rq_inflight(struct blk_mq_hw_ctx hctx, struct request rq,
		void *priv, bool reserved)
		{
		/*
		* If we find a request that is inflight and the queue matches,
		* If we find a request that isn't idle and the queue matches,
		* we know the queue is busy. Return false to stop the iteration.
		*/
		if (rq->state == MQ_RQ_IN_FLIGHT && rq->q == hctx->queue) {
		if (blk_mq_request_started(rq) && rq->q == hctx->queue) {
		bool *busy = priv;

		*busy = true;

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