On Tue, Dec 21, 2021 at 8:15 PM Muchun Song [off-list ref] wrote:

[...]

quoted

+static inline void mod_memcg_page_state(struct page *page,
+                                       int idx, int val)
+{
+       struct mem_cgroup *memcg = page_memcg(page);
+
+       if (!mem_cgroup_disabled() && memcg)
+               mod_memcg_state(memcg, idx, val);

It's not safe to access @memcg throughout mod_memcg_state() for the
kmem charged through objcg infrastructure. It's supposed to be safe
to access @memcg under rcu read lock. Otherwise, it looks good to
me.

Indeed you are right. v2 coming.