[PATCH resend] block: silently error unsupported empty barriers too

From: Mark McLoughlin
Date: Thu Sep 03 2009 - 11:49:49 EST

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 <mpatocka@xxxxxxxxxx>
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:


Signed-off-by: Mark McLoughlin <markmc@xxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Cc: Alasdair G Kergon <agk@xxxxxxxxxx>
Cc: Neil Brown <neilb@xxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
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;

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