bio->bi_bdev = sc->stripe[stripe].dev->bdev;
bio->bi_sector = sc->stripe[stripe].physical_start +
(chunk << sc->chunk_shift) + (offset & sc->chunk_mask);
bio->bi_bdev = sc->stripe[stripe].dev->bdev;
bio->bi_sector = sc->stripe[stripe].physical_start +
(chunk << sc->chunk_shift) + (offset & sc->chunk_mask);