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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1772711825; 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=MMHHbOrsvMEf7fKsOGegfWk7YRVFbtR0jAiLvTiMweo=; b=mDHzNUEqAQqp7SL0gmqequ7wqLe6seQrDyt4SxyM3fHn/DvPTQvI5jYPRoQYMnXXn+LlcW wmz1cq6L2WlD5784mqCaAOhK+e8AJDvNjI5x1EIKMdRyQDa/cS71gR+Lr6mLQ9MVqyXQXs 07pwy8XxAKhcCGpQBwjvKf2U6ifeoWw= 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, Qi Zheng Subject: [PATCH v6 17/33] mm: thp: prevent memory cgroup release in folio_split_queue_lock{_irqsave}() Date: Thu, 5 Mar 2026 19:52:35 +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: rspam11 X-Rspamd-Queue-Id: 0640D80004 X-Stat-Signature: mn5fdsffd49kewz7e1guxp7fayfyam4p X-HE-Tag: 1772711826-920150 X-HE-Meta: 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 QqwPG0XR btnzWb5gaQdrtR58iopMxupgb3ad0nGUV5wSiVlhhwJ6SxjPpmm0K0wDsxE5Vnm/yttRtNbzAkbb6rGgiN0FBX5Rb1xoKMbKTDOBJDEJZZBhLJ2s2RyBTMIko6n3NMQPswn2P7JxxtfaPgzAWa30VGEhAv278Oxg1DsES5GdbZ0YMo1uTXAkD4oYHPB1nBei16cAGwy632b9gFFrley3WMMvnkVeCzZ6xIpEwBwoURxzemE5Jzh0eDREFWX69TEIBfR66pvIQ4OJq+tqVctiBHoH89hCNcGCOiNO5rPgPBSAQo+ToUqz0d5HDNa5e5QUmHBY5dI4i1sCtzhtcxdM/M30h4g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Qi Zheng 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 folio_split_queue_lock{_irqsave}(). Signed-off-by: Qi Zheng Reviewed-by: Harry Yoo Acked-by: Johannes Weiner Acked-by: Shakeel Butt Acked-by: David Hildenbrand (Red Hat) Acked-by: Muchun Song --- mm/huge_memory.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index f6c0a86055bdc..56db54fa48181 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1157,13 +1157,29 @@ split_queue_lock_irqsave(int nid, struct mem_cgroup *memcg, unsigned long *flags static struct deferred_split *folio_split_queue_lock(struct folio *folio) { - return split_queue_lock(folio_nid(folio), folio_memcg(folio)); + struct deferred_split *queue; + + rcu_read_lock(); + queue = split_queue_lock(folio_nid(folio), folio_memcg(folio)); + /* + * The memcg destruction path is acquiring the split queue lock for + * reparenting. Once you have it locked, it's safe to drop the rcu lock. + */ + rcu_read_unlock(); + + return queue; } static struct deferred_split * folio_split_queue_lock_irqsave(struct folio *folio, unsigned long *flags) { - return split_queue_lock_irqsave(folio_nid(folio), folio_memcg(folio), flags); + struct deferred_split *queue; + + rcu_read_lock(); + queue = split_queue_lock_irqsave(folio_nid(folio), folio_memcg(folio), flags); + rcu_read_unlock(); + + return queue; } static inline void split_queue_unlock(struct deferred_split *queue) -- 2.20.1