On Tue, Oct 27, 2020 at 8:50 PM Muchun Song <songmuchun@xxxxxxxxxxxxx> wrote:
>
> Consider the following memcg hierarchy.
>
> root
> / \
> A B
>
> If we get the objcg of memcg A failed,
Please fix the above statement.
> the get_obj_cgroup_from_current
> can return the wrong objcg for the root memcg.
>
> Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API")
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> ---
> changelog in v2:
> 1. Do not use a comparison with the root_mem_cgroup
>
> mm/memcontrol.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 1337775b04f3..8c8b4c3ed5a0 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2961,6 +2961,7 @@ __always_inline struct obj_cgroup *get_obj_cgroup_from_current(void)
> objcg = rcu_dereference(memcg->objcg);
> if (objcg && obj_cgroup_tryget(objcg))
> break;
> + objcg = NULL;
Roman, in your cleanup, are you planning to have objcg for root memcg as well?
> }
> rcu_read_unlock();
>
> --
> 2.20.1
>
