def parent_link_update_from_dirrecord(self):
        # type: () -> None
        '''
        Update the logical extent number stored in the parent link record (if
        there is one), from the directory record entry that was stored in
        the parent_link member.  This is used at the end of reshuffling extents
        to properly update the parent link records.

        Parameters:
         None.
        Returns:
         Nothing.
        '''
        if not self._initialized:
            raise pycdlibexception.PyCdlibInternalError('Rock Ridge extension not yet initialized')

        if self.parent_link is None:
            raise pycdlibexception.PyCdlibInvalidInput('No parent link found!')

        if self.dr_entries.pl_record is not None:
            self.dr_entries.pl_record.set_log_block_num(self.parent_link.extent_location())
        elif self.ce_entries.pl_record is not None:
            self.ce_entries.pl_record.set_log_block_num(self.parent_link.extent_location())
        else:
            raise pycdlibexception.PyCdlibInvalidInput('Could not find parent link record!')