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

[Roman Gushchin <guro@fb.com>]

On Tue, May 26, 2020 at 09:25:25AM +0800, Zefan Li 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@cmpxchg.org>
> Signed-off-by: Zefan Li <lizefan@huawei.com>
> ---

Reviewed-by: Roman Gushchin <guro@fb.com>

Thanks!

> 
> 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
>