[PATCH 1/1] UBUNTU: [Upstream] block: silently error unsupported empty barriers too

[Stefan Bader]

Should get used to that now...

Andy Whitcroft wrote:
> BugLink: http://bugs.launchpad.net/bugs/420423
> Patch: http://patchwork.kernel.org/patch/39589/
> 
> 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 at redhat.com>
>     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 <markmc at redhat.com>
> Cc: Rusty Russell <rusty at rustcorp.com.au>
> Cc: Mikulas Patocka <mpatocka at redhat.com>
> Cc: Alasdair G Kergon <agk at redhat.com>
> Cc: Neil Brown <neilb at suse.de>
> Signed-off-by: Andy Whitcroft <apw at canonical.com>

Acked-by: Stefan Bader <stefan.bader at canonical.com>

> ---
>  block/blk-core.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index e3299a7..af20cbd 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -1163,7 +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) &&
> +	if (bio_barrier(bio) &&
>  	    (q->next_ordered == QUEUE_ORDERED_NONE)) {
>  		bio_endio(bio, -EOPNOTSUPP);
>  		return 0;