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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1772711762; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=uFugfqe6/ZOVEb7BRYdC4hEvLiQEcyW+5o69Lqfswgk=; b=Sp5oK5oFjJ4WgSWliPpVc97gKNr6NqbPwLiwIZw2Z5SdXlWR5qqaGTuz0QH15VeaTPFeTL DhNfLnKGRBoCG/NKALOxn+6rpvwZ+0MFsAYZK5mRe2jhWsni/vOgmp0glTUg1xHKOXNwk2 OXk+yVV6975l6Mvz8Y7qKdWdSI/kOaA= From: Qi Zheng To: hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, harry.yoo@oracle.com, yosry.ahmed@linux.dev, imran.f.khan@oracle.com, kamalesh.babulal@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, chenridong@huaweicloud.com, mkoutny@suse.com, akpm@linux-foundation.org, hamzamahfooz@linux.microsoft.com, apais@linux.microsoft.com, lance.yang@linux.dev, bhe@redhat.com, usamaarif642@gmail.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng Subject: [PATCH v6 11/33] mm: memcontrol: prevent memory cgroup release in count_memcg_folio_events() Date: Thu, 5 Mar 2026 19:52:29 +0800 Message-ID: In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 9DA89100011 X-Stat-Signature: aso6pwxk3zd4n9soyjpui1denstnaz9c X-Rspam-User: X-HE-Tag: 1772711765-836959 X-HE-Meta: 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 pge5vwwI o+Ft3GTKE5OIVLGYjfpsbOQQg9aEBV2U30W06dRCuoHRaEMJRZEI98ROKQKYqAr0qrnZfx/HmMMZ/dQUQ5m43r3LkT4DBAeo/AqlJPcY6hwQFp1pO+wsZUzL6LlhBCLJXhgOIuTwA7uHOQc5g7qlfeLqblHQ04cYjLoDI5RPGXiEE2W9D/J6Cb3cQvYv5VBpK7GHPduw7YLHaFXxOsGFR5jK6nEIr9bY2N5VzqKlsyPQUBR+dr6wsnwe7kPTrBx/JkYcGs9P1Relc0YW006l+CLLDzjtfeicsLPqeFGvHgGmfNs46cSH4TKCUMnB84TTPEimE3qLppD1Ctbr74BWrXOUFxjvHu8rgOJt0 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Muchun Song In the near future, a folio will no longer pin its corresponding memory cgroup. To ensure safety, it will only be appropriate to hold the rcu read lock or acquire a reference to the memory cgroup returned by folio_memcg(), thereby preventing it from being released. In the current patch, the rcu read lock is employed to safeguard against the release of the memory cgroup in count_memcg_folio_events(). This serves as a preparatory measure for the reparenting of the LRU pages. Signed-off-by: Muchun Song Signed-off-by: Qi Zheng Reviewed-by: Harry Yoo Acked-by: Johannes Weiner Acked-by: Shakeel Butt --- include/linux/memcontrol.h | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 20d38262b984b..0fdfb8044458e 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -976,10 +976,15 @@ void count_memcg_events(struct mem_cgroup *memcg, enum vm_event_item idx, static inline void count_memcg_folio_events(struct folio *folio, enum vm_event_item idx, unsigned long nr) { - struct mem_cgroup *memcg = folio_memcg(folio); + struct mem_cgroup *memcg; - if (memcg) - count_memcg_events(memcg, idx, nr); + if (!folio_memcg_charged(folio)) + return; + + rcu_read_lock(); + memcg = folio_memcg(folio); + count_memcg_events(memcg, idx, nr); + rcu_read_unlock(); } static inline void count_memcg_events_mm(struct mm_struct *mm, -- 2.20.1