On 05/17/2016 10:51 AM, Kevin Wolf wrote:
> From: "Denis V. Lunev" <den@openvz.org>
> 
> We should check for (res & BDRV_BLOCK_ZERO) only. The situation when we
> will have !(res & BDRV_BLOCK_DATA) and will not have BDRV_BLOCK_ZERO is
> not possible for images with bdi.unallocated_blocks_are_zero == true.
> 
> For those images where it's false, however, it can happen and we must
> not consider the data zeroed then or we would corrupt the image.
> 
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Kevin Wolf <kwolf@redhat.com>
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/qcow2.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org