bch_btree_insert
int bch_btree_insert(struct cache_set *c, struct keylist *keys,
ret = bch_btree_insert(s, &keylist, i->pin, NULL);
ret = bch_btree_insert(op->c, &op->insert_keys,
ret = bch_btree_insert(dc->disk.c, &keys, NULL, &w->key);