From: Mark McLoughlin Subject: [PATCH] block: silently error unsupported empty barriers too With 2.6.31-rc5 in a KVM guest using dm and virtio_blk, we see the following errors: end_request: I/O error, dev vda, sector 0 end_request: I/O error, dev vda, sector 0 The errors go away if dm stops submitting empty barriers, by reverting: commit 52b1fd5a27c625c78373e024bf570af3c9d44a79 Author: Mikulas Patocka dm: send empty barriers to targets in dm_flush We should error all barriers, even empty barriers, on devices like virtio_blk which don't support them. See also: https://bugzilla.redhat.com/514901 Signed-off-by: Mark McLoughlin Cc: Rusty Russell Cc: Mikulas Patocka Cc: Alasdair G Kergon Cc: Neil Brown --- block/blk-core.c | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index e3299a7..35ad2bb 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1163,8 +1163,7 @@ static int __make_request(struct request_queue *q, struct bio *bio) const int unplug = bio_unplug(bio); int rw_flags; - if (bio_barrier(bio) && bio_has_data(bio) && - (q->next_ordered == QUEUE_ORDERED_NONE)) { + if (bio_barrier(bio) && (q->next_ordered == QUEUE_ORDERED_NONE)) { bio_endio(bio, -EOPNOTSUPP); return 0; } -- 1.6.4