Patch "dm rq: fix a race condition in rq_completed()" has been added to the 4.9-stable tree

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

dm rq: fix a race condition in rq_completed()

to the 4.9-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-fix-a-race-condition-in-rq_completed.patch
and it can be found in the queue-4.9 subdirectory.

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

From: Bart Van Assche <[email protected]>
Date: Fri, 11 Nov 2016 17:05:27 -0800
Subject: dm rq: fix a race condition in rq_completed()

From: Bart Van Assche <[email protected]>

commit d15bb3a6467e102e60d954aadda5fb19ce6fd8ec upstream.

It is required to hold the queue lock when calling blk_run_queue_async() to avoid that a race between blk_run_queue_async() and blk_cleanup_queue() is triggered.

---
 drivers/md/dm-rq.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

@@ -226,6 +226,9 @@ static void rq_end_stats(struct mapped_d
  */
 static void rq_completed(struct mapped_device *md, int rw, bool run_queue)
 {
+	struct request_queue *q = md->queue;
+	unsigned long flags;
+
 	atomic_dec(&md->pending[rw]);
 
 	/* nudge anyone waiting on suspend queue */

@@ -238,8 +241,11 @@ static void rq_completed(struct mapped_d
 	 * back into ->request_fn() could deadlock attempting to grab the
 	 * queue lock again.
 	 */
-	if (!md->queue->mq_ops && run_queue)
-		blk_run_queue_async(md->queue);
+	if (!q->mq_ops && run_queue) {
+		spin_lock_irqsave(q->queue_lock, flags);
+		blk_run_queue_async(q);
+		spin_unlock_irqrestore(q->queue_lock, flags);
+	}
 
 	/*
 	 * dm_put() must be at the end of this function. See the comment above

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

queue-4.9/dm-rq-fix-a-race-condition-in-rq_completed.patch queue-4.9/blk-mq-do-not-invoke-.queue_rq-for-a-stopped-queue.patch queue-4.9/dm-table-fix-all_blk_mq-inconsistency-when-an-empty-table-is-loaded.patch queue-4.9/dm-table-an-all_blk_mq-table-must-be-loaded-for-a-blk-mq-dm-device.patch