def METHOD_NAME(self, m):
    opt_set = set()
    if m.fs_type == "xfs":
        opt_set.add("nouuid")
    if m.mount_options is None:
        opt_set.add("ro")
        return ','.join(opt_set)
    opt_set |= set(m.mount_options.split(','))
    opt_set -= set(['rw', 'ro'])
    opt_set |= set(['ro'])
    return ','.join(opt_set)