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Date: Thu, 16 Jun 2016 15:38:27 +0800
From: Fam Zheng <famz@redhat.com>
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In-Reply-To: <1466060287-31514-3-git-send-email-den@openvz.org>
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>
Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>, Stefan Hajnoczi <stefanha@redhat.com>, Kevin Wolf <kwolf@redhat.com>, Max Reitz <mreitz@redhat.com>

On Thu, 06/16 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,
> +                   req.bytes << BDRV_SECTOR_BITS);
>      tracked_request_end(&req);
>      return ret;
>  }
> -- 
> 2.5.0
> 

Reviewed-by: Fam Zheng <famz@redhat.com>