read_block_for_search
ret2 = read_block_for_search(root, p, &b, slot, key);
ret2 = read_block_for_search(root, p, &b, slot, key);
ret = read_block_for_search(root, path, &next, slot, &key);
ret = read_block_for_search(root, path, &next, 0, &key);