btrfs_set_inode_index
int btrfs_set_inode_index(struct btrfs_inode *dir, u64 *index);
ret = btrfs_set_inode_index(BTRFS_I(dir), &BTRFS_I(inode)->dir_index);
ret = btrfs_set_inode_index(BTRFS_I(dir), &index);
ret = btrfs_set_inode_index(BTRFS_I(new_dir), &old_idx);
ret = btrfs_set_inode_index(BTRFS_I(old_dir), &new_idx);
ret = btrfs_set_inode_index(BTRFS_I(new_dir), &index);
ret = btrfs_set_inode_index(parent_inode, &index);