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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1772005873; 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=YnqQdkxjJbx1HzdwiQPOBZhqi2P1B4b2zXofX9tiSXRbhKT9I1/WPJy/OUavIlU+LGKZm8 aICEhysMrnj0hqLpt+QiHOtPnJdAQBbYD4AnTpf3XUfccibxw2WJgi5UicTv8TTbtPtjv/ mJtq1WEfhDHT78dursyOZX0mlHOSaNw= 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 v5 11/32] mm: memcontrol: prevent memory cgroup release in count_memcg_folio_events() Date: Wed, 25 Feb 2026 15:48:44 +0800 Message-ID: In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 0A3158000A X-Stat-Signature: ncfgprj7c5fz9yfdfapokz69cahow85t X-HE-Tag: 1772005874-762631 X-HE-Meta: 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 IZuw0mok AWbdsp0AvEnpeQ+ZT0HxnptotD5COgt1JQRJqfIV+LfiWv8TdS4gvGuJg3b/apfbXPePJ37oYNRqUZZoqg4D1jq+ilblrSgzDoysyGLbW68SDhyvk46qyYKGMK8oTzhedbgMhTvcLgUr8FVJoWD/+6NMxwscg+3fPHOZR99lRKgpAYE6ZHZmkj5NNMzd2SFEbn3C2LnhzxXkHQ/u1WMcL3+v70duHxiF1eknusRxtnxJ/iNkspfhyDvgG5Zdwkjao3O1RJdt/S3m8vePF2ihc56eO6qGqfsavGorTRSCmSR3WoQAIc85vm4hYEjN/9fMgc6CmnkIRlBoYgcXWLZrEKEIRDVzlW85gwXH1 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