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Wed, 17 Dec 2025 13:45:53 -0800 (PST) Received: from localhost ([2603:7000:c01:2716:929a:4aff:fe16:c778]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-88c617699c5sm3733236d6.57.2025.12.17.13.45.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Dec 2025 13:45:53 -0800 (PST) Date: Wed, 17 Dec 2025 16:45:52 -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 09/28] buffer: prevent memory cgroup release in folio_alloc_buffers() Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: A9F36140010 X-Stat-Signature: c1u5g9apgzs1c817pnbbfxqso4sdjpuh X-Rspam-User: X-HE-Tag: 1766007954-264736 X-HE-Meta: U2FsdGVkX19qE81MEkhqG8pcXtRuFxxom7LWYVYKBnQ9kdvNQWGKaXXBpLACeWcrQfGANV+jSGxcsNlgDkezqLYauBBh/oeeDFExfRNRHIBd2MeT7KJPpQ1zIPfFfhrng+8jS/Rrec+svN1g6JziFFmd6lI4tO5S6XMquZr4/6XxeBacQLalCXTYMBBdwEymdT88m8PdLR5A+51nhqIt9iA6mUc2b3eyJE2040Ly8FULc2TxJyYPJQc0KZzl2Me7N0wZ4pqNw24FrlmhEwq2P2J43rdWDOKoBjc/Zi8zILZ2CLtQ3EECuJ2knh721TsDB6ggGQtDC+XmUMbZ+wQ8SK4xOH1bvaaU6i+Ufj7p7bC1/oU9z6FtNjUp27Ajj2zPAdBpIawIgyMnMmXhPOZ13mbJjbni0v+9ts/DrElwlwHmLYWTdPJiofK1KCCOq1ToEHpFHlE+sBYiwYcMZ/qHpEzLNiRdfSrLhtYUrJnEcPkSKtmdtDtLY+R1+1c+2klyzdsjJoxwmHTZ0t4q0vtJuXxbPbtScYom2rBRMYGn9ytvktfrp6uFVF/hAXklHdOK7LVvRZL/ZD1VzJtkhpVH1QMFtq+hTw8qxM3U9bBSIen21Ca/BSkTvb9Ueqa1ldumkV/Q8xwF+QMP3MiKW9dartPJdBu6SAe3yV3Jguq3SziZzYSCW4SmkccUT+NzqjBGY4lb4A+Kg6X75jzWdw9/kvmPHEeJkeK47dLkwR09Ov9nsUtd672GkfOkHBdUVGMaa6BgGIyxMGv8qc32q4FG4UD9iZ92cQnLMi6o9TYL//MlChhQ9j/ossYF7WDNpktHAU6qQ2SgDsRGVxVC5FQg6Bj11pjkxQQUR+PrnsGtDQozO2gxfx4v4gqKGlu641l9NpFc6KUilz77vhcUCy9nHpGxJrPmdx2l1IeL7AiaFnsmc4NH5n9JVz5dECqxtTNq9Ci+yzFl1VojS/UVIPN ZB242jMI 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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 03:27:33PM +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 function get_mem_cgroup_from_folio() is > employed to safeguard against the release of the memory cgroup. > 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