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From: "Denis V. Lunev" <den@openvz.org>
Message-ID: <576273BF.70806@openvz.org>
Date: Thu, 16 Jun 2016 12:39:11 +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: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>, 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 06/16/2016 12:34 PM, Vladimir Sementsov-Ogievskiy wrote:
> 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;
>>   }
>
>
very nice, thanks ;)