From: Usama Arif <usama.arif@linux.dev>
To: Johannes Weiner <hannes@cmpxchg.org>,
Andrew Morton <akpm@linux-foundation.org>
Cc: David Hildenbrand <david@kernel.org>,
Lorenzo Stoakes <ljs@kernel.org>,
Shakeel Butt <shakeel.butt@linux.dev>,
Michal Hocko <mhocko@kernel.org>,
Dave Chinner <david@fromorbit.com>,
Roman Gushchin <roman.gushchin@linux.dev>,
Muchun Song <muchun.song@linux.dev>,
Qi Zheng <qi.zheng@linux.dev>,
Yosry Ahmed <yosry.ahmed@linux.dev>, Zi Yan <ziy@nvidia.com>,
"Liam R . Howlett" <liam@infradead.org>,
Kiryl Shutsemau <kas@kernel.org>,
Vlastimil Babka <vbabka@kernel.org>,
Kairui Song <ryncsn@gmail.com>,
Mikhail Zaslonko <zaslonko@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
Barry Song <baohua@kernel.org>, Dev Jain <dev.jain@arm.com>,
Lance Yang <lance.yang@linux.dev>, Nico Pache <npache@redhat.com>,
Ryan Roberts <ryan.roberts@arm.com>,
cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 1/9] mm: list_lru: fix set_shrinker_bit() call during race with cgroup deletion
Date: Thu, 28 May 2026 14:25:10 +0100 [thread overview]
Message-ID: <1eb96ce9-6959-403a-980c-c3bbd5843bbf@linux.dev> (raw)
In-Reply-To: <20260527204757.2544958-2-hannes@cmpxchg.org>
On 27/05/2026 21:45, Johannes Weiner wrote:
> When list_lru_add() races with cgroup deletion, the shrinker bit is set
> on the wrong group and lost. This can cause a shrinker run to miss the
> cgroup that actually has the object.
>
> When the passed in memcg is dead, the function finds the first non-dead
> parent from the passed in memcg and adds the object there; but the
> shrinker bit is set on the memcg that was passed in.
>
> This bug is as old as the shrinker bitmap itself.
>
> Fix it by returning the "effective" memcg from the locking function, and
> have the caller use that.
>
> Fixes: fae91d6d8be5 ("mm/list_lru.c: set bit in memcg shrinker bitmap on first list_lru item appearance")
> Reported-by: Usama Arif <usama.arif@linux.dev>
> Reported-by: Sashiko
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> ---
> mm/list_lru.c | 26 +++++++++++++++-----------
> 1 file changed, 15 insertions(+), 11 deletions(-)
>
Acked-by: Usama Arif <usama.arif@linux.dev>
next prev parent reply other threads:[~2026-05-28 13:25 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-27 20:45 [PATCH v5 0/9] mm: switch THP shrinker to list_lru Johannes Weiner
2026-05-27 20:45 ` [PATCH v5 1/9] mm: list_lru: fix set_shrinker_bit() call during race with cgroup deletion Johannes Weiner
2026-05-28 13:25 ` Usama Arif [this message]
2026-05-30 2:38 ` Wei Yang
2026-05-27 20:45 ` [PATCH v5 2/9] mm: list_lru: lock_list_lru_of_memcg() cannot return NULL if !skip_empty Johannes Weiner
2026-05-27 20:45 ` [PATCH v5 3/9] mm: list_lru: deduplicate unlock_list_lru() Johannes Weiner
2026-05-27 20:45 ` [PATCH v5 4/9] mm: list_lru: move list dead check to lock_list_lru_of_memcg() Johannes Weiner
2026-05-27 20:45 ` [PATCH v5 5/9] mm: list_lru: deduplicate lock_list_lru() Johannes Weiner
2026-05-29 9:56 ` Wei Yang
2026-05-29 13:42 ` Johannes Weiner
2026-05-30 1:25 ` Wei Yang
2026-05-27 20:45 ` [PATCH v5 6/9] mm: list_lru: introduce caller locking for additions and deletions Johannes Weiner
2026-05-27 20:45 ` [PATCH v5 7/9] mm: list_lru: introduce folio_memcg_list_lru_alloc() Johannes Weiner
2026-05-27 20:45 ` [PATCH v5 8/9] mm: memory: flatten alloc_anon_folio() retry loop Johannes Weiner
2026-05-30 9:06 ` Dev Jain
2026-05-27 20:45 ` [PATCH v5 9/9] mm: switch deferred split shrinker to list_lru Johannes Weiner
2026-05-28 7:08 ` SeongJae Park
2026-05-28 14:03 ` Johannes Weiner
2026-05-28 13:32 ` Usama Arif
2026-05-28 14:02 ` Johannes Weiner
2026-05-28 15:31 ` Usama Arif
2026-05-29 17:33 ` Kairui Song
2026-05-31 8:00 ` Wei Yang
2026-06-01 10:39 ` Lance Yang
2026-06-01 11:09 ` Lance Yang
2026-06-01 13:21 ` Lance Yang
2026-06-01 18:17 ` Johannes Weiner
2026-06-01 8:36 ` [PATCH v5 0/9] mm: switch THP " Lance Yang
2026-06-02 21:46 ` Johannes Weiner
2026-06-03 4:44 ` Lance Yang
2026-06-03 11:41 ` Johannes Weiner
2026-06-03 11:53 ` Lance Yang
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