From: Mike Snitzer <snitzer@redhat.com>
Date: Thu, 1 Sep 2016 15:59:33 +0000 (-0400)
Subject: dm rq: take request_queue lock while clearing QUEUE_FLAG_STOPPED
X-Git-Tag: v4.9-rc1~70^2~20
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=9dbeaeabacb26260d1621fe58f0f6fdedc8860d4;p=karo-tx-linux.git

dm rq: take request_queue lock while clearing QUEUE_FLAG_STOPPED

Every call of queue_flag_clear_unlocked() after block device
initialization has finished is wrong if blk_cleanup_queue() can be
called concurrently.  Convert queue_flag_clear_unlocked() into
queue_flag_clear() and protect it by the block layer queue lock.

Also, factor out dm_mq_start_queue().

Reported-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
---

diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 2f605f62e47d..bd3ba97d44a2 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -73,15 +73,24 @@ static void dm_old_start_queue(struct request_queue *q)
 	spin_unlock_irqrestore(q->queue_lock, flags);
 }
 
+static void dm_mq_start_queue(struct request_queue *q)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	queue_flag_clear(QUEUE_FLAG_STOPPED, q);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+
+	blk_mq_start_stopped_hw_queues(q, true);
+	blk_mq_kick_requeue_list(q);
+}
+
 void dm_start_queue(struct request_queue *q)
 {
 	if (!q->mq_ops)
 		dm_old_start_queue(q);
-	else {
-		queue_flag_clear_unlocked(QUEUE_FLAG_STOPPED, q);
-		blk_mq_start_stopped_hw_queues(q, true);
-		blk_mq_kick_requeue_list(q);
-	}
+	else
+		dm_mq_start_queue(q);
 }
 
 static void dm_old_stop_queue(struct request_queue *q)