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

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Message-ID: <iwmabnye3nl4merealrawt3bdvfii2pwavwrddrqpraoveet7h@ezrsdhjwwej7>
Date: Fri, 25 Oct 2024 23:34:34 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: 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 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?


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 */