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Wed, 17 Dec 2025 14:12:59 -0800 (PST) Received: from localhost ([2603:7000:c01:2716:929a:4aff:fe16:c778]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8beebb3ab66sm35932785a.48.2025.12.17.14.12.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Dec 2025 14:12:58 -0800 (PST) Date: Wed, 17 Dec 2025 17:12:56 -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 12/28] mm: page_io: prevent memory cgroup release in page_io module Message-ID: References: <30588f984137d557e4663ae8dcf398b8c408169b.1765956025.git.zhengqi.arch@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <30588f984137d557e4663ae8dcf398b8c408169b.1765956025.git.zhengqi.arch@bytedance.com> X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 0FC421C0010 X-Stat-Signature: zyn8xeqmxwsftgwatzkwuq7gczarjcqz X-HE-Tag: 1766009579-948527 X-HE-Meta: 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 h+bK2V9d 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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 03:27:36PM +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 swap_writeout() and > bio_associate_blkg_from_page(). > > 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