Comment 10 for bug 1436314

Hmmm actually it won't:

        # NOTE(johannes): root_gb is allowed to be 0 for legacy reasons
        # since libvirt interpreted the value differently than other
        # drivers. A value of 0 means don't check size.
        root_gb = instance_type['root_gb']
        if root_gb:
            if int(image.get('size') or 0) > root_gb * (1024 ** 3):
                raise exception.FlavorDiskTooSmall()

            if int(image.get('min_disk') or 0) > root_gb:
                    raise exception.FlavorDiskTooSmall()

It seems like flavor is still the natural place to have this (as opposed to a global disable.