Re: [PATCH 1/9] memcg: accounting for allocations called with disabled BH

[Roman Gushchin <guro@fb.com>]

On Tue, Mar 09, 2021 at 11:03:48AM +0300, Vasily Averin wrote:
> in_interrupt() check in memcg_kmem_bypass() is incorrect because
> it does not allow to account memory allocation called from task context
> with disabled BH, i.e. inside spin_lock_bh()/spin_unlock_bh() sections
> 
> Signed-off-by: Vasily Averin <vvs@virtuozzo.com>

Good catch!

It looks like the bug was there for years: in_interrupt() was there since
the commit 7ae1e1d0f8ac ("memcg: kmem controller infrastructure") from 2012!
So I guess there is no point for a stable fix, but it's definitely nice to
have it fixed.

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

for this patch and the rest of the series.

Thank you!

> ---
>  mm/memcontrol.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 845eec0..568f2cb 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1076,7 +1076,7 @@ static __always_inline bool memcg_kmem_bypass(void)
>  		return false;
>  
>  	/* Memcg to charge can't be determined. */
> -	if (in_interrupt() || !current->mm || (current->flags & PF_KTHREAD))
> +	if (!in_task() || !current->mm || (current->flags & PF_KTHREAD))
>  		return true;
>  
>  	return false;
> -- 
> 1.8.3.1
>