---

yaml
---
r: 209155
b: refs/heads/master
c: 708e929
h: refs/heads/master
i:
  209153: c145a16
  209151: b53da4c
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 87c961cb747fa55b664b76abfcb9d44c14ae851f
+refs/heads/master: 708e929513502fb050c0a3c3ee267cab5b056ded

trunk/drivers/md/dm.c

@@ -639,8 +639,14 @@ static void dec_pending(struct dm_io *io, int error)
 			 * There can be just one barrier request so we use
 			 * a per-device variable for error reporting.
 			 * Note that you can't touch the bio after end_io_acct
+			 *
+			 * We ignore -EOPNOTSUPP for empty flush reported by
+			 * underlying devices. We assume that if the device
+			 * doesn't support empty barriers, it doesn't need
+			 * cache flushing commands.
 			 */
-			if (!md->barrier_error && io_error != -EOPNOTSUPP)
+			if (!md->barrier_error &&
+			    !(bio_empty_barrier(bio) && io_error == -EOPNOTSUPP))
 				md->barrier_error = io_error;
 			end_io_acct(io);
 			free_io(md, io);
@@ -2284,7 +2290,12 @@ static void process_barrier(struct mapped_device *md, struct bio *bio)
 
 	if (!bio_empty_barrier(bio)) {
 		__split_and_process_bio(md, bio);
-		dm_flush(md);
+		/*
+		 * If the request isn't supported, don't waste time with
+		 * the second flush.
+		 */
+		if (md->barrier_error != -EOPNOTSUPP)
+			dm_flush(md);
 	}
 
 	if (md->barrier_error != DM_ENDIO_REQUEUE)