linux-kernel - [PATCH 4.14 201/228] dm rq: dont call blk_mq_queue_stopped() in dm_stop

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Date:   Thu, 20 Aug 2020 11:22:56 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ming Lei <ming.lei@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.14 201/228] dm rq: dont call blk_mq_queue_stopped() in dm_stop_queue()

From: Ming Lei <ming.lei@...hat.com>

[ Upstream commit e766668c6cd49d741cfb49eaeb38998ba34d27bc ]

dm_stop_queue() only uses blk_mq_quiesce_queue() so it doesn't
formally stop the blk-mq queue; therefore there is no point making the
blk_mq_queue_stopped() check -- it will never be stopped.

In addition, even though dm_stop_queue() actually tries to quiesce hw
queues via blk_mq_quiesce_queue(), checking with blk_queue_quiesced()
to avoid unnecessary queue quiesce isn't reliable because: the
QUEUE_FLAG_QUIESCED flag is set before synchronize_rcu() and
dm_stop_queue() may be called when synchronize_rcu() from another
blk_mq_quiesce_queue() is in-progress.

Fixes: 7b17c2f7292ba ("dm: Fix a race condition related to stopping and starting queues")
Signed-off-by: Ming Lei <ming.lei@...hat.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/md/dm-rq.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index eadfcfd106fff..cac8ec16e6031 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -95,9 +95,6 @@ static void dm_old_stop_queue(struct request_queue *q)

 static void dm_mq_stop_queue(struct request_queue *q)
 {
-	if (blk_mq_queue_stopped(q))
-		return;
-
 	blk_mq_quiesce_queue(q);
 }

-- 
2.25.1