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From: Pavel Butsykin <pbutsykin@virtuozzo.com>
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Date: Tue, 28 Jun 2016 15:32:13 +0300
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Subject: Re: [Qemu-devel] [PATCH 07/11] block: optimization
 blk_pwrite_compressed()
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To: Kevin Wolf <kwolf@redhat.com>, "Denis V. Lunev" <den@openvz.org>
Cc: qemu-devel@nongnu.org, Jeff Cody <jcody@redhat.com>, Markus Armbruster <armbru@redhat.com>, Eric Blake <eblake@redhat.com>, John Snow <jsnow@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>

On 28.06.2016 14:47, Kevin Wolf wrote:
> Am 31.05.2016 um 11:15 hat Denis V. Lunev geschrieben:
>> From: Pavel Butsykin <pbutsykin@virtuozzo.com>
>>
>> For bdrv_pwrite_compressed() it looks like most of the code creating coroutine
>> is duplicated in blk_prw(). So we can just add a flag(BDRV_REQ_WRITE_COMPRESSED)
>> and use the blk_prw() as a generic one.
>>
>> Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
>> Signed-off-by: Denis V. Lunev <den@openvz.org>
>> CC: Jeff Cody <jcody@redhat.com>
>> CC: Markus Armbruster <armbru@redhat.com>
>> CC: Eric Blake <eblake@redhat.com>
>> CC: John Snow <jsnow@redhat.com>
>> CC: Stefan Hajnoczi <stefanha@redhat.com>
>> CC: Kevin Wolf <kwolf@redhat.com>
>
> Oh, so you already do use a flag. Nice. :-)
>
>> diff --git a/block/block-backend.c b/block/block-backend.c
>> index 3c1fc50..9e1c793 100644
>> --- a/block/block-backend.c
>> +++ b/block/block-backend.c
>> @@ -785,7 +785,11 @@ int coroutine_fn blk_co_pwritev(BlockBackend *blk, int64_t offset,
>>           flags |= BDRV_REQ_FUA;
>>       }
>>
>> -    return bdrv_co_pwritev(blk_bs(blk), offset, bytes, qiov, flags);
>> +    if (flags & BDRV_REQ_WRITE_COMPRESSED) {
>> +        return bdrv_co_pwritev_compressed(blk_bs(blk), offset, bytes, qiov);
>> +    } else {
>> +        return bdrv_co_pwritev(blk_bs(blk), offset, bytes, qiov, flags);
>> +    }
>>   }
>
> If you move the processing of the flag inside bdrv_co_pwritev(), where I
> think it belongs anyway, you could use the flag from the start (by going
> through bdrv_prwv_co()) instead of temporarily introducing your own
> coroutine wrapper. I think that would make the initial conversion
> patches quite a bit simpler.

You propose to add bdrv_driver_compressed and call it from 
bdrv_aligned_pwritev ?

> Kevin
>