bch_submit_bbio
void bch_submit_bbio(struct bio *bio, struct cache_set *c,
bch_submit_bbio(bio, b->c, &b->key, 0);
bch_submit_bbio(b->bio, b->c, &k.key, 0);
bch_submit_bbio(b->bio, b->c, &k.key, 0);
bch_submit_bbio(bio, io->op.c, &io->w->key, 0);
bch_submit_bbio(n, op->c, k, 0);
bch_submit_bbio(bio, c, k, i);