On 28.06.20 13:02, Alberto Garcia wrote:
> The QCOW_OFLAG_ZERO bit that indicates that a cluster reads as
> zeroes is only used in standard L2 entries. Extended L2 entries use
> individual 'all zeroes' bits for each subcluster.
> 
> This must be taken into account when updating the L2 entry and also
> when deciding that an existing entry does not need to be updated.
> 
> Signed-off-by: Alberto Garcia <berto@igalia.com>
> Reviewed-by: Eric Blake <eblake@redhat.com>
> ---
>  block/qcow2-cluster.c | 36 +++++++++++++++++++-----------------
>  1 file changed, 19 insertions(+), 17 deletions(-)

Reviewed-by: Max Reitz <mreitz@redhat.com>