STATX_MNT_ID
stat->result_mask |= STATX_MNT_ID;
{ STATX_MNT_ID, "MNT_ID" }, \
old_parent_id = get_mnt_id("parent", root_mntpoint, STATX_MNT_ID);
old_root_id = get_mnt_id("root", "/", STATX_MNT_ID);