dm rq: fix a race condition in rq_completed()

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.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 8 insertions, 2 deletions

diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 1d0d2adc050a..31a89c8832c0 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -226,6 +226,9 @@ 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 */
@@ -238,8 +241,11 @@ 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