code: func UdevWait(cookie *uint) error {
  	if res := DmUdevWait(*cookie); res != 1 {
  		logrus.Debugf("devicemapper: Failed to wait on udev cookie %d, %d", *cookie, res)
  		return ErrUdevWait
  	}
  	return nil
  }
docs: // UdevWait waits for any processes that are waiting for udev to complete the specified cookie.