__swap_cgroup_get
*memcg_id = __swap_cgroup_get(ci, ci_off);
(memcg_id && *memcg_id != __swap_cgroup_get(ci, ci_off))))
unsigned short old = __swap_cgroup_get(ci, ci_off);
WARN_ON_ONCE(__swap_cgroup_get(ci, ci_off));