def rollback(self, context, reservations, project_id=None, user_id=None):

        try:
            self._driver.rollback(context, reservations, project_id=project_id,
                                  user_id=user_id)
        except Exception:
            # NOTE(Vek): Ignoring exceptions here is safe, because the
            # usage resynchronization and the reservation expiration
            # mechanisms will resolve the issue.  The exception is
            # logged, however, because this is less than optimal.
            LOG.exception(_LE("Failed to roll back reservations %s"),
                          reservations)
            return
        LOG.debug("Rolled back reservations %s", reservations)
Roll back reservations.
dataset/ETHPy150Open openstack/nova/nova/quota.py/QuotaEngine.rollback