Re: [Qemu-block] [Qemu-devel] callout to *file in bdrv_co_get_block_status

[Paolo Bonzini]

On 20/03/2017 14:35, Peter Lieven wrote:
> Am 20.03.2017 um 14:23 schrieb Paolo Bonzini:
>> On 20/03/2017 14:13, Peter Lieven wrote:
>>> Am 20.03.2017 um 13:47 schrieb Peter Lieven:
>>>> commit 5daa74a6ebce7543aaad178c4061dc087bb4c705
>>>> Author: Paolo Bonzini <address@hidden>
>>>> Date:   Wed Sep 4 19:00:38 2013 +0200
>>>>
>>>>     block: look for zero blocks in bs->file
>>>>    
>>>>     Reviewed-by: Eric Blake <address@hidden>
>>>>     Signed-off-by: Paolo Bonzini <address@hidden>
>>>>     Signed-off-by: Stefan Hajnoczi <address@hidden>
>>>>
>>>>
>>>> It was introduced while introducing bdv_get_block_status. I don't know 
>>>> what the real
>>>>
>>>> issue was that was addressed with this patch?
>>> Is it possible that this optimization was added especially for RAW? I was 
>>> believing that
>>> raw would forward the get_block_status call to bs->file, but it looks it 
>>> doesn't.
>>> If this one here was for RAW would it be an option to move this callout to 
>>> the raw-format driver
>>> and remove it from the generic code?
>> It was meant for both raw and qcow2.
> 
> Okay, but as Fam mentioned qcow2 Metadata should know that a cluster is zero. 
> Do you remember
> what the issue was?

I said that already---preallocated metadata.  Also, at the time
pre-qcow2v3 was more important.

Are you using libiscsi, block devices or files?

Paolo