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Wed, 17 Dec 2025 14:11:15 -0800 (PST) Received: from localhost ([2603:7000:c01:2716:929a:4aff:fe16:c778]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8beeba3c1aesm34819685a.46.2025.12.17.14.11.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Dec 2025 14:11:14 -0800 (PST) Date: Wed, 17 Dec 2025 17:11:13 -0500 From: Johannes Weiner To: Qi Zheng Cc: 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, 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, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng Subject: Re: [PATCH v2 11/28] mm: memcontrol: prevent memory cgroup release in count_memcg_folio_events() Message-ID: References: <5f8032bc300b7c12e61446ba4f3d28fba5a7d9d5.1765956025.git.zhengqi.arch@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5f8032bc300b7c12e61446ba4f3d28fba5a7d9d5.1765956025.git.zhengqi.arch@bytedance.com> X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 5D4991C000C X-Stat-Signature: ckw8855zdpxqnrtpwjjtbct8rcnmjqc8 X-Rspam-User: X-HE-Tag: 1766009476-374 X-HE-Meta: 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 C2ETn6I9 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Dec 17, 2025 at 03:27:35PM +0800, Qi Zheng wrote: > 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