From 650badd18a5816546745986e2f2c439bf76a04eb Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@redhat.com>
Date: Fri, 19 Jun 2020 16:42:14 +0800
Subject: [PATCH] dm rq: don't call blk_mq_queue_stopped() in dm_stop_queue()

commit e766668c6cd49d741cfb49eaeb38998ba34d27bc upstream.

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@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index b41ecb451c78..99784f16cb56 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -70,9 +70,6 @@ void dm_start_queue(struct request_queue *q)
 
 void dm_stop_queue(struct request_queue *q)
 {
-	if (blk_mq_queue_stopped(q))
-		return;
-
 	blk_mq_quiesce_queue(q);
 }
 
-- 
2.27.0