[dm-devel] [PATCH 03/14] dm: Fix a race condition in rq_completed()

[Bart Van Assche]

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.

Signed-off-by: Bart Van Assche <bart.vanassche at sandisk.com>
---
 drivers/md/dm-rq.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index f9f37ad..7df7948 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -210,6 +210,9 @@ static void rq_end_stats(struct mapped_device *md, struct request *orig)
  */
 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 */
@@ -222,8 +225,11 @@ static void rq_completed(struct mapped_device *md, int rw, bool run_queue)
 	 * 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
-- 
2.10.1