bio_seg_gap
rq->phys_gap_bit = bio_seg_gap(rq->q, rq->biotail, bio,
req->phys_gap_bit = bio_seg_gap(req->q, req->biotail, next->bio,
req->phys_gap_bit = bio_seg_gap(req->q, req->biotail, bio,
req->phys_gap_bit = bio_seg_gap(req->q, bio, req->bio,
u8 bio_seg_gap(struct request_queue *q, struct bio *prev, struct bio *next,