1 files changed, 18 insertions, 0 deletions

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 39fddda2fef2..55b5e0e77b17 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1470,7 +1470,25 @@ static void raid10_make_request(struct mddev *mddev, struct bio *bio)
                         split = bio;
                 }
 
+                /*
+                 * If a bio is splitted, the first part of bio will pass
+                 * barrier but the bio is queued in current->bio_list (see
+                 * generic_make_request). If there is a raise_barrier() called
+                 * here, the second part of bio can't pass barrier. But since
+                 * the first part bio isn't dispatched to underlaying disks
+                 * yet, the barrier is never released, hence raise_barrier will
+                 * alays wait. We have a deadlock.
+                 * Note, this only happens in read path. For write path, the
+                 * first part of bio is dispatched in a schedule() call
+                 * (because of blk plug) or offloaded to raid10d.
+                 * Quitting from the function immediately can change the bio
+                 * order queued in bio_list and avoid the deadlock.
+                 */
                 __make_request(mddev, split);
+                if (split != bio && bio_data_dir(bio) == READ) {
+                        generic_make_request(bio);
+                        break;
+                }
         } while (split != bio);
 
         /* In case raid10d snuck in to freeze_array */