Re: [PATCH] memcg: Fix memcg_kmem_bypass() for remote memcg charging

Michal Hocko
2020-05-13T09:05:02Z

On Wed 13-05-20 15:28:28, Li Zefan wrote:
> While trying to use remote memcg charging in an out-of-tree kernel module
> I found it's not working, because the current thread is a workqueue thread.
>
> Signed-off-by: Zefan Li <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
> ---
>
> No need to queue this for v5.7 as currently no upstream users of this memcg
> feature suffer from this bug.
>
> ---
> mm/memcontrol.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index a3b97f1..db836fc 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2802,6 +2802,8 @@ static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
>
> static inline bool memcg_kmem_bypass(void)
> {
> + if (unlikely(current->active_memcg))
> + return false;

I am confused. Why the check below is insufficient? It checks for both mm
and PF_KTHREAD?

> if (in_interrupt() || !current->mm || (current->flags & PF_KTHREAD))
> return true;
> return false;
> --
> 2.7.4

--
Michal Hocko
SUSE Labs