[Qemu-devel] Re: [PATCH v3] qcow2: Implement bdrv_truncate() for growing images

[Kevin Wolf <kwolf@redhat.com>]

Am 28.04.2010 12:36, schrieb Stefan Hajnoczi:
> This patch adds the ability to grow qcow2 images in-place using
> bdrv_truncate().  This enables qemu-img resize command support for
> qcow2.
> 
> Snapshots are not supported and bdrv_truncate() will return -ENOTSUP.
> The notion of resizing an image with snapshots could lead to confusion:
> users may expect snapshots to remain unchanged, but this is not possible
> with the current qcow2 on-disk format where the header.size field is
> global instead of per-snapshot.  Others may expect snapshots to change
> size along with the current image data.  I think it is safest to not
> support snapshots and perhaps add behavior later if there is a
> consensus.
> 
> Backing images continue to work.  If the image is now larger than its
> backing image, zeroes are read when accessing beyond the end of the
> backing image.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

Thanks, applied to the block branch.

Kevin