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Date: Fri, 13 Sep 2013 11:14:08 +0200
From: Peter Lieven <pl@kamp.de>
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Subject: Re: [Qemu-devel] [PULL 39/42] block: look for zero blocks in
	bs->file
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Anthony Liguori <anthony@codemonkey.ws>, Peter Lieven <lieven-lists@dlhnet.de>, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>

On 13.09.2013 11:10, Paolo Bonzini wrote:
> Il 13/09/2013 11:08, Peter Lieven ha scritto:
>> On 13.09.2013 10:00, Peter Lieven wrote:
>>> On 06.09.2013 17:39, Stefan Hajnoczi wrote:
>>>> From: Paolo Bonzini <pbonzini@redhat.com>
>>>>
>>>> Reviewed-by: Eric Blake <eblake@redhat.com>
>>>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>>>> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
>>>> ---
>>>>    block.c | 16 +++++++++++++++-
>>>>    1 file changed, 15 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/block.c b/block.c
>>>> index 3c39769..a325efc 100644
>>>> --- a/block.c
>>>> +++ b/block.c
>>>> @@ -3075,7 +3075,7 @@ static int64_t coroutine_fn
>>>> bdrv_co_get_block_status(BlockDriverState *bs,
>>>>    {
>>>>        int64_t length;
>>>>        int64_t n;
>>>> -    int64_t ret;
>>>> +    int64_t ret, ret2;
>>>>          length = bdrv_getlength(bs);
>>>>        if (length < 0) {
>>>> @@ -3117,6 +3117,20 @@ static int64_t coroutine_fn
>>>> bdrv_co_get_block_status(BlockDriverState *bs,
>>>>                }
>>>>            }
>>>>        }
>>>> +
>>>> +    if (bs->file &&
>>>> +        (ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
>>>> +        (ret & BDRV_BLOCK_OFFSET_VALID)) {
>>>> +        ret2 = bdrv_co_get_block_status(bs->file, ret >>
>>>> BDRV_SECTOR_BITS,
>>>> +                                        *pnum, pnum);
>>>> +        if (ret2 >= 0) {
>>>> +            /* Ignore errors.  This is just providing extra
>>>> information, it
>>>> +             * is useful but not necessary.
>>>> +             */
>>>> +            ret |= (ret2 & BDRV_BLOCK_ZERO);
>>>> +        }
>>>> +    }
>>>> +
>>>>        return ret;
>>>>    }
>>> for allocated blocks in iscsi this actually leads to 2 call outs to
>>> iscsi_get_block_status.
>>>
>>> because the raw driver passes the get_block_status request to bs->file.
>>>
>> correct patch?
> Correct but a bit hackish... Stefan, Kevin, any ideas?
add a BDRV_BLOCK_RAW flag to the get_block_status flags?