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Date: Tue, 16 Jul 2013 09:19:12 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 16/17] block: add default get_block_status
 implementation for protocols
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To: Peter Lieven <pl@kamp.de>
Cc: kwolf@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com

Il 16/07/2013 08:47, Peter Lieven ha scritto:
>>
>> @@ -2977,7 +2977,11 @@ static int64_t coroutine_fn
>> bdrv_co_get_block_status(BlockDriverState *bs,
>>         if (!bs->drv->bdrv_co_get_block_status) {
>>           *pnum = nb_sectors;
>> -        return BDRV_BLOCK_DATA;
>> +        ret = BDRV_BLOCK_DATA;
>> +        if (bs->drv->protocol_name) {
>> +            ret |= BDRV_BLOCK_OFFSET_VALID | (sector_num *
>> BDRV_SECTOR_SIZE);
>> +        }
>> +        return ret;
>>       }
>>         ret = bs->drv->bdrv_co_get_block_status(bs, sector_num,
>> nb_sectors, pnum);
> I am curious if this is right. Doesn't this mean we say that at offset
> sector_num * BDRV_SECTOR_SIZE are nb_sectors of linear data? This is
> something we do not know for sure.

Only for protocols.  In this case, we do know, or format=raw wouldn't
work.  This is not propagated up to the actual BDS for the image, except
for format=raw.

Paolo