readahead_expand
readahead_expand(ractl, ra_pos, em_end - ra_pos);
readahead_expand(rac, headoffset, cur - headoffset);
readahead_expand(ractl, rreq->start, rreq->len);
readahead_expand(rac, new_start, new_len);
readahead_expand(ractl, start, (len | mask) + 1);
void readahead_expand(struct readahead_control *ractl,
EXPORT_SYMBOL(readahead_expand);