'Return size of volume for manage_existing.'

def _manage_existing_get_size(self, volume, existing_ref):

    ldev = self._string2int(existing_ref.get('ldev'))
    if (ldev is None):
        msg = basic_lib.output_err(701)
        raise exception.HBSDError(data=msg)
    size = self.command.get_ldev_size_in_gigabyte(ldev, existing_ref)
    metadata = {'type': basic_lib.NORMAL_VOLUME_TYPE, 'ldev': ldev}
    self._update_volume_metadata(volume['id'], metadata)
    return size
