'Use driver or generic method to rollback volume.'

def _revert_to_snapshot(self, context, volume, snapshot):

    self._notify_about_volume_usage(context, volume, 'revert.start')
    self._notify_about_snapshot_usage(context, snapshot, 'revert.start')
    try:
        self.driver.revert_to_snapshot(context, volume, snapshot)
    except (NotImplementedError, AttributeError):
        LOG.info("Driver's    'revert_to_snapshot'    is    not    found.    Try    to    use    copy-snapshot-to-volume    method.")
        self._revert_to_snapshot_generic(context, volume, snapshot)
    self._notify_about_volume_usage(context, volume, 'revert.end')
    self._notify_about_snapshot_usage(context, snapshot, 'revert.end')
