meta_bucket_bytes
((meta_bucket_bytes(&(ca)->sb) - sizeof(struct prio_set)) / \
c->nr_uuids = meta_bucket_bytes(sb) / sizeof(struct uuid_entry);
bio->bi_iter.bi_size = meta_bucket_bytes(&ca->sb);
p->csum = bch_crc64(&p->magic, meta_bucket_bytes(&ca->sb) - 8);
bch_crc64(&p->magic, meta_bucket_bytes(&ca->sb) - 8)) {