bch_btree_insert_keys
bch_btree_insert_keys(n1, op, insert_keys, replace_key);
bch_btree_insert_keys(n1, op, insert_keys, replace_key);
bch_btree_insert_keys(n3, op, &parent_keys, NULL);
if (bch_btree_insert_keys(b, op, insert_keys, replace_key)) {