r5_next_bio
wbi2 = r5_next_bio(conf, wbi, dev->sector);
rbi2 = r5_next_bio(conf, rbi, dev->sector);
rbi = r5_next_bio(conf, rbi, dev->sector);
wbi = r5_next_bio(conf, wbi, dev->sector);
bi = r5_next_bio(conf, bi, sh->dev[dd_idx].sector)) {
struct bio *nextbi = r5_next_bio(conf, bi, sh->dev[i].sector);
struct bio *bi2 = r5_next_bio(conf, bi, sh->dev[i].sector);
r5_next_bio(conf, bi, sh->dev[i].sector);
wbi2 = r5_next_bio(conf, wbi, dev->sector);