This allows us to differentiate between filters and nodes with COW
backing files: Filters cannot be used as overlays at all (for this
function).
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
goto out;
}
- if (state->new_bs->backing != NULL) {
+ if (state->new_bs->drv->is_filter) {
+ error_setg(errp, "Filters cannot be used as overlays");
+ goto out;
+ }
+
+ if (bdrv_cow_child(state->new_bs)) {
error_setg(errp, "The overlay already has a backing image");
goto out;
}