mm/memcg: non-hierarchical mode is deprecated

After commit bef8620cd8e0 ("mm: memcg: deprecate the non-hierarchical
mode"), we won't have a NULL parent except root_mem_cgroup.  And this case
is handled when (memcg == root).

Link: https://lkml.kernel.org/r/20220403020833.26164-1-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1ae0a2a..b2d5c66 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6587,9 +6587,6 @@ void mem_cgroup_calculate_protection(struct mem_cgroup *root,
                return;
 
        parent = parent_mem_cgroup(memcg);
-       /* No parent means a non-hierarchical mode on v1 memcg */
-       if (!parent)
-               return;
 
        if (parent == root) {
                memcg->memory.emin = READ_ONCE(memcg->memory.min);