Merge tag 'for-4.16/dm-chained-bios-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm

Pull device mapper fix from Mike Snitzer:
 "Fix for DM core to properly propagate errors (avoids overriding
  non-zero error with 0). This is particularly important given DM core's
  increased use of chained bios"

* tag 'for-4.16/dm-chained-bios-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
  dm: correctly handle chained bios in dec_pending()

drivers/md/dm.c

@@ -903,7 +903,8 @@ static void dec_pending(struct dm_io *io, blk_status_t error)
 			queue_io(md, bio);
 		} else {
 			/* done with normal IO or empty flush */
-			bio->bi_status = io_error;
+			if (io_error)
+				bio->bi_status = io_error;
 			bio_endio(bio);
 		}
 	}