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From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-ID: <5762728E.4090407@virtuozzo.com>
Date: Thu, 16 Jun 2016 12:34:06 +0300
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Subject: Re: [Qemu-devel] [PATCH 2/3] block: fix race in bdrv_co_discard
 with drive-mirror
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To: "Denis V. Lunev" <den@openvz.org>, qemu-devel@nongnu.org, qemu-block@nongnu.org
Cc: Stefan Hajnoczi <stefanha@redhat.com>, Fam Zheng <famz@redhat.com>, Kevin Wolf <kwolf@redhat.com>, Max Reitz <mreitz@redhat.com>

On 16.06.2016 09:58, Denis V. Lunev wrote:
> Actually we must set dirty bitmap dirty after we have written all our
> zeroes for correct processing in drive mirror code. In the other case
> we can face not zeroes in this dirty area there in mirror_iteration.
>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Vladimir Sementsov-Ogievskiy<vsementsov@virtuozzo.com>
> CC: Stefan Hajnoczi <stefanha@redhat.com>
> CC: Fam Zheng <famz@redhat.com>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Max Reitz <mreitz@redhat.com>
> ---
>   block/io.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/block/io.c b/block/io.c
> index b51f681..513bd99 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -2265,7 +2265,6 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
>   
>       tracked_request_begin(&req, bs, NULL, sector_num << BDRV_SECTOR_BITS,
>                             nb_sectors << BDRV_SECTOR_BITS, BDRV_TRACKED_DISCARD);
> -    bdrv_set_dirty(bs, sector_num, nb_sectors);
>   
>       max_discard = MIN_NON_ZERO(bs->bl.max_discard, BDRV_REQUEST_MAX_SECTORS);
>       while (nb_sectors > 0) {
> @@ -2314,6 +2313,8 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
>       }
>       ret = 0;
>   out:
> +    bdrv_set_dirty(bs, req.offset << BDRV_SECTOR_BITS,
  s/<</>>/
> +                   req.bytes << BDRV_SECTOR_BITS);
and here
>       tracked_request_end(&req);
>       return ret;
>   }


-- 
Best regards,
Vladimir