Patch "dm rq: take request_queue lock while clearing QUEUE_FLAG_STOPPED" has been added to the 4.8-stable tree

This is a note to let you know that I've just added the patch titled

dm rq: take request_queue lock while clearing QUEUE_FLAG_STOPPED

to the 4.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
dm-rq-take-request_queue-lock-while-clearing-queue_flag_stopped.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Mike Snitzer <[email protected]>
Date: Thu, 1 Sep 2016 11:59:33 -0400
Subject: dm rq: take request_queue lock while clearing QUEUE_FLAG_STOPPED

From: Mike Snitzer <[email protected]>

commit 9dbeaeabacb26260d1621fe58f0f6fdedc8860d4 upstream.

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().

---
 drivers/md/dm-rq.c |   19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

@@ -73,15 +73,24 @@ static void dm_old_start_queue(struct re
 	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)

Patches currently in stable-queue which might be from [email protected] are

queue-4.8/dm-crypt-fix-crash-on-exit.patch queue-4.8/dm-rq-take-request_queue-lock-while-clearing-queue_flag_stopped.patch queue-4.8/dm-mark-request_queue-dead-before-destroying-the-dm-device.patch queue-4.8/dm-mpath-check-if-path-s-request_queue-is-dying-in-activate_path.patch queue-4.8/dm-return-correct-error-code-in-dm_resume-s-retry-loop.patch