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Date: Mon, 10 Aug 2026 11:47:49 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Guopeng Zhang <guopeng.zhang@linux.dev>
Cc: shakeel.butt@linux.dev, hannes@cmpxchg.org, mhocko@kernel.org,
 roman.gushchin@linux.dev, muchun.song@linux.dev, cgroups@vger.kernel.org,
 linux-mm@kvack.org, linux-kernel@vger.kernel.org, Guopeng Zhang
 <zhangguopeng@kylinos.cn>
Subject: Re: [PATCH] mm: memcg-v1: fix memory.memsw.failcnt accounting
Message-Id: <20260810114749.368140ad5be4fa10085bbee0@linux-foundation.org>
In-Reply-To: <20260810074247.52747-1-guopeng.zhang@linux.dev>
References: <20260810074247.52747-1-guopeng.zhang@linux.dev>
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On Mon, 10 Aug 2026 15:42:47 +0800 Guopeng Zhang <guopeng.zhang@linux.dev> wrote:

> Commit 0e2759afcaf9 ("page_counter: track failcnt only for legacy
> cgroups") made failcnt accounting conditional on track_failcnt. It
> enabled the flag for memcg->memory, but not for memcg->memsw.
> 
> Consequently, memory.memsw.failcnt remains zero when the memory+swap
> limit is hit. Enable failcnt accounting for the v1 memsw counter.
> 
> Reproducer:
> 
>     CG=/sys/fs/cgroup/memory/memsw-test
>     LIMIT=33554432
>     mkdir "$CG"
>     echo "$LIMIT" > "$CG/memory.limit_in_bytes"
>     echo "$LIMIT" > "$CG/memory.memsw.limit_in_bytes"
> 
> Start a child process in the cgroup and make it allocate and touch 96 MiB
> of memory, causing a memcg OOM.
> 
>     cat "$CG/memory.memsw.failcnt"
> 
> Without the patch, memory.memsw.failcnt is 0. With the patch,
> memory.memsw.failcnt is greater than 0.

Thanks.  Nice changelog.

> Fixes: 0e2759afcaf9 ("page_counter: track failcnt only for legacy cgroups")

I'll add cc:stable to this.

AI review thinks that memcg->tcpmem.track_failcnt should receive the
same treatment:

	https://sashiko.dev/#/patchset/20260810074247.52747-1-guopeng.zhang@linux.dev