1 files changed, 13 insertions, 1 deletions

diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index c63044e9c4c0..8eba4e43bb0c 100644
--- a/block/blk-barrier.c
+++ b/block/blk-barrier.c
@@ -166,9 +166,21 @@ static inline bool start_ordered(struct request_queue *q, struct request **rqp)
          * For an empty barrier, there's no actual BAR request, which
          * in turn makes POSTFLUSH unnecessary.  Mask them off.
          */
-        if (!rq->hard_nr_sectors)
+        if (!rq->hard_nr_sectors) {
                 q->ordered &= ~(QUEUE_ORDERED_DO_BAR |
                                 QUEUE_ORDERED_DO_POSTFLUSH);
+                /*
+                 * Empty barrier on a write-through device w/ ordered
+                 * tag has no command to issue and without any command
+                 * to issue, ordering by tag can't be used.  Drain
+                 * instead.
+                 */
+                if ((q->ordered & QUEUE_ORDERED_BY_TAG) &&
+                    !(q->ordered & QUEUE_ORDERED_DO_PREFLUSH)) {
+                        q->ordered &= ~QUEUE_ORDERED_BY_TAG;
+                        q->ordered |= QUEUE_ORDERED_BY_DRAIN;
+                }
+        }
 
         /* stash away the original request */
         elv_dequeue_request(q, rq);