rq_mergeable
if (rq_mergeable(rq)) {
if (!rq_mergeable(req) || !rq_mergeable(next))
if (!rq_mergeable(rq) || !bio_mergeable(bio))
return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq, free);
if (unlikely(!rq_mergeable(rq))) {
if (rq_mergeable(rq)) {