Re: [PATCH v3] memcg: Fix memcg_kmem_bypass() for remote memcg charging

Michal Hocko
2020-05-28T14:44:10Z

On Tue 26-05-20 09:25:25, 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.
>
> As we will probably encounter this issue in the future as the users of
> memalloc_use_memcg() grow, and it's nothing wrong for this usage, it's
> better we fix it now.
>
> Acked-by: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
> Signed-off-by: Zefan Li <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>

Acked-by: Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org>

> ---
>
> v3: bypass __GFP_ACCOUNT allocations in interrupt contexts.
>
> ---
> mm/memcontrol.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index a3b97f1..3c7717a 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2802,7 +2802,12 @@ static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
>
> static inline bool memcg_kmem_bypass(void)
> {
> - if (in_interrupt() || !current->mm || (current->flags & PF_KTHREAD))
> + if (in_interrupt())
> + return true;
> +
> + /* Allow remote memcg charging in kthread contexts. */
> + if ((!current->mm || (current->flags & PF_KTHREAD)) &&
> + !current->active_memcg)
> return true;
> return false;
> }
> --
> 2.7.4

--
Michal Hocko
SUSE Labs