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From: Shakeel Butt To: Qi Zheng Cc: hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@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-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: D333880007 X-Stat-Signature: djgbwf6e1jmqpg9eprq9sozzffpsh3xu X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1766187114-558670 X-HE-Meta: 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 UNj71FIt c6sF6i0BHb5QeOADrytlVFm53aS1H3zl8trM2uSqXX2otsKKTjzM7+bbxrWGyvaayYOGVbTlblDwCCZpkYIg8EOG2SkXUoGHZ5KA5vgnVtu6cyHK1/9S3jpLzwpxwKhhn31Mz6MIS2sga+7UgGex3RBbU5sa58EzzddsZf01S+OqZilFX1EWKQC0JJEH1tEGAUsLZnnpygmuxcBURtfX/DdrwB6MMvnz0lbR95sy9XneQU3wIQTYQbieCrmCo1mgrvoeX1ax43TjO/mP4GAlxASjjLFeyEcWbgWpot1VsiJKLK3jgOY21BvAQWz4BEPvo3gpqxHl8ppbSuic= 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: Shakeel Butt