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Wed, 17 Dec 2025 14:14:23 -0800 (PST) Received: from localhost ([2603:7000:c01:2716:929a:4aff:fe16:c778]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-88c6089a7c3sm4446836d6.27.2025.12.17.14.14.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Dec 2025 14:14:23 -0800 (PST) Date: Wed, 17 Dec 2025 17:14:22 -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 13/28] mm: migrate: prevent memory cgroup release in folio_migrate_mapping() Message-ID: References: <1554459c705a46324b83799ede617b670b9e22fb.1765956025.git.zhengqi.arch@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1554459c705a46324b83799ede617b670b9e22fb.1765956025.git.zhengqi.arch@bytedance.com> X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: A516180008 X-Stat-Signature: gh5nc3s6saxep14ffxo1rxnf8nhse3ge X-Rspam-User: X-HE-Tag: 1766009664-88357 X-HE-Meta: U2FsdGVkX19HAIrZ4hqI2f+61bjHhSMFqGa2sAH3nww520X4Ype4Au/humtd+8BDMneVg8rHEcTtj0PsqKrQhkUsonuvsi90tREpITvZaV2Dwi9Yg8U9CsIvfmwjxbhbwhoYrdyl37h2h7LNdsuH0PRGhJbxKpsaI2PP1hC1MNq7QrQakOp//cTJZ260L8O3HoKeKoRJFYNYHC6UQ4YsCs92jTcQdAjA8fBwm6KlFRjAKd0ScxlfFzNfZVZ3E8ws506mnMURrdcU6i4MSUxCy5k/DdC4uBUe6uZyX1osGBCdFlKBgmbSIV4z1Hqw/rKOsy6iGFeDxIYxtnCKudIky6DHcPKQSuVKHlTyEl5+REhlQhlnZN406tEpS7xgAlyPY7ltOXfEyGzcuaNqkbhsuzJMcQiY3h2VFckr116K7ca0crHGruJHklhfoFfGGuIKnqwL6k9yJV/6gGrxWS/RpWlzQuN0iF6SQoJq/9PRUiXGx0EoUBgjubXDLlqxh9/VgZqq1N5CBjlVdKJr/WrX6XOTjwpCLlQvTFwU8OnMOEQQrow5Ft3tqYO4uOJJzb6IgXkmH0wgmfWlcw7p5BSoubpIUM5cZyr5geGpm/tfO5LCa6DIHgxFikFoQX9acapytSnPRrN4fFAvX0GDDiU7fYAGk+0rWBGJWJCVoSFzr90Awkte+mLwQi10nkMecTh37q7Nc4BJXNe4+6qG5H22aD8idl92NjmyGL00S0c0CZduEToJgC+xvlbwVeFVpecDhzHzmNdjNEKrGj3LVI1TKQbcSF/rK73EmMMguZLXNTh7oeyqmbYGCUlAJ1HvvkiutKiWJFh3RwW6t3t8wlx/YhDwfSYxecEFIPXUuOrT/q0NvjYhv1n7Ti6lG3c/rpnONNaYYOYuwmRZuPErIhc8jVfXOQqkNRYkpo9+PaVboP3GzxeUMdoG4vl8aSrnYJs9BA44L8rfRgXDpBXEj2/ F02VssMb 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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 03:27:37PM +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 folio_migrate_mapping(). > > 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