On Mon, Apr 03, 2017 at 06:09:29PM +0200, Max Reitz wrote:
> This patch adds two new parameters to the preallocate() function so we
> will be able to use it not just for preallocating a new image but also
> for preallocated image growth.
> 
> The offset parameter allows the caller to specify a virtual offset from
> which to start preallocating. For newly created images this is always 0,
> but for preallocating growth this will be the old image length.
> 
> The new_length parameter specifies the supposed new length of the image
> (basically the "end offset" for preallocation). During image truncation,
> bdrv_getlength() will return the old image length so we cannot rely on
> its return value then.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/qcow2.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>