bio_attempt_back_merge
return bio_attempt_back_merge(rq, bio, nr_segs);
if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
if (bio_attempt_back_merge(req, bio, bio->__bi_nr_segments) !=
enum bio_merge_status bio_attempt_back_merge(struct request *req,