Re: [PATCH v3 14/16] qcow2: Fix v3 snapshot table entry compliancy

[Eric Blake <eblake@redhat.com>]

On 10/11/19 10:28 AM, Max Reitz wrote:
> qcow2 v3 images require every snapshot table entry to have at least 16
> bytes of extra data.  If they do not, let qemu-img check -r all fix it.
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> Reviewed-by: Eric Blake <eblake@redhat.com>
> ---
>   block/qcow2-snapshot.c | 18 ++++++++++++++++++
>   1 file changed, 18 insertions(+)
> 
> diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
> index dac8a778e4..5ab64da1ec 100644
> --- a/block/qcow2-snapshot.c
> +++ b/block/qcow2-snapshot.c
> @@ -516,6 +516,24 @@ int coroutine_fn qcow2_check_read_snapshot_table(BlockDriverState *bs,
>           result->corruptions -= nb_clusters_reduced;
>       }
>   
> +    /*
> +     * All of v3 images' snapshot table entries need to have at least
> +     * 16 bytes of extra data.
> +     */
> +    if (s->qcow_version >= 3) {
> +        int i;
> +        for (i = 0; i < s->nb_snapshots; i++) {
> +            if (s->snapshots[i].extra_data_size <
> +                sizeof_field(QCowSnapshotExtraData, vm_state_size_large) +
> +                sizeof_field(QCowSnapshotExtraData, disk_size))
> +            {

Another stylistic place where sizeof(QCowSnapshotExtraData) would be 
more compact.  Doesn't change R-b

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org