Re: [Qemu-devel] [PATCH] qcow2: Allow qcow2 disk images with size zero

[Kevin Wolf]

Am 27.10.2009 15:11, schrieb Anthony Liguori:
> Stefan Weil wrote:
>> Images with disk size 0 may be used for
>> VM snapshots, but not to save normal block data.
>>
>> It is possible to create such images using
>> qemu-img, but opening them later fails.
>>
>> So even "qemu-img info image.qcow2" is not
>> possible for an image created with
>> "qemu-img create -f qcow2 image.qcow2 0".
>>
>> This is fixed here.
>>
>> Signed-off-by: Stefan Weil <address@hidden>
>>   
> 
> What do you think Kevin?

That with malloc instead of qemu_malloc the patch would have been a bit
smaller. ;-) I think it can make sense to have such images in some cases
(although a 64k image isn't much worse) and I don't see any obvious
problem with the patch. Not sure how guests like 0 byte disks, but I
assume Stefan has tested that.

I'm just wondering how Stefan did create his test image - with current
qemu-img I can't create such images, so I needed to patch it first. For
this one I'll send a fix.

Kevin