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Date: Thu, 17 Sep 2026 20:49:01 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Hongfu Li <hongfu.li@linux.dev>
Cc: Muchun Song <muchun.song@linux.dev>, Oscar Salvador <osalvador@suse.de>,
 David Hildenbrand <david@kernel.org>, Kees Cook <kees@kernel.org>, Colin
 Ian King <colin.i.king@gmail.com>, Shakeel Butt <shakeel.butt@linux.dev>,
 Mina Almasry <almasrymina@google.com>, Mike Kravetz
 <mike.kravetz@oracle.com>, linux-mm@kvack.org,
 linux-kernel@vger.kernel.org, Hongfu Li <lihongfu@kylinos.cn>,
 stable@vger.kernel.org
Subject: Re: [PATCH v2 0/2] mm/hugetlb_cgroup: move the per-node usage along
 with the folio
Message-Id: <20260917204901.efd6e6908c85c104467fdeff@linux-foundation.org>
In-Reply-To: <20260918-for-hugetlb-charge-v2-0-2b6d8c2bdc36@kylinos.cn>
References: <20260918-for-hugetlb-charge-v2-0-2b6d8c2bdc36@kylinos.cn>
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On Fri, 18 Sep 2026 10:56:09 +0800 Hongfu Li <hongfu.li@linux.dev> wrote:

> The per-node usage reported by hugetlb.<size>.numa_stat is accounted
> against folio_nid() in __hugetlb_cgroup_commit_charge() and
> __hugetlb_cgroup_uncharge_folio(), so it is only correct while a folio
> stays charged on the same node and in the same hugetlb_cgroup.
> 
> Two paths move a folio which stays charged, and neither moves the usage
> with it. hugetlb_cgroup_migrate() only moves the hugetlb_cgroup pointers
> of a folio migrated to another node, and hugetlb_cgroup_move_parent()
> only moves the page_counter charges and the hugetlb_cgroup pointer of
> the folios of a dying cgroup. In both cases the node (or cgroup) which
> was charged keeps a usage which never goes away, while the node
> (or cgroup) which ends up uncharging the folio underflows as soon as
> the folio is freed.

Thanks.

> Fixes: f47761999052 ("hugetlb: add hugetlb.*.numa_stat file")
> Cc: stable@vger.kernel.org

I'll queue these for the next merge window, with cc:stable.  I don't
see a hurry to fix a four year old bug.