linux-kernel - Re: [PATCH v1 5/6] memcg-v1: no need for memcg locking for MGLRU

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Message-ID: <CAOUHufZexpg-m5rqJXUvkCh5nS6RqJYcaS9b=xra--pVnHctPA@mail.gmail.com>
Date: Sat, 26 Oct 2024 09:26:04 -0600
From: Yu Zhao <yuzhao@...gle.com>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Johannes Weiner <hannes@...xchg.org>, 
	Michal Hocko <mhocko@...nel.org>, Roman Gushchin <roman.gushchin@...ux.dev>, 
	Muchun Song <muchun.song@...ux.dev>, Hugh Dickins <hughd@...gle.com>, 
	Yosry Ahmed <yosryahmed@...gle.com>, linux-mm@...ck.org, cgroups@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	linux-doc@...r.kernel.org, Meta kernel team <kernel-team@...a.com>
Subject: Re: [PATCH v1 5/6] memcg-v1: no need for memcg locking for MGLRU

On Sat, Oct 26, 2024 at 12:34 AM Shakeel Butt <shakeel.butt@...ux.dev> wrote:
>
> On Thu, Oct 24, 2024 at 06:23:02PM GMT, Shakeel Butt wrote:
> > While updating the generation of the folios, MGLRU requires that the
> > folio's memcg association remains stable. With the charge migration
> > deprecated, there is no need for MGLRU to acquire locks to keep the
> > folio and memcg association stable.
> >
> > Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
>
> Andrew, can you please apply the following fix to this patch after your
> unused fixup?

Thanks!

> index fd7171658b63..b8b0e8fa1332 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -3353,7 +3353,7 @@ static struct folio *get_pfn_folio(unsigned long pfn, struct mem_cgroup *memcg,
>         if (folio_nid(folio) != pgdat->node_id)
>                 return NULL;
>
> -       if (folio_memcg_rcu(folio) != memcg)
> +       if (folio_memcg(folio) != memcg)
>                 return NULL;
>
>         /* file VMAs can contain anon pages from COW */
>
>