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Wed, 17 Dec 2025 14:21:22 -0800 (PST) Received: from localhost ([2603:7000:c01:2716:929a:4aff:fe16:c778]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-88c5dc716besm4640426d6.2.2025.12.17.14.21.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Dec 2025 14:21:22 -0800 (PST) Date: Wed, 17 Dec 2025 17:21:21 -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 15/28] mm: memcontrol: prevent memory cgroup release in mem_cgroup_swap_full() Message-ID: References: <4dd1fb48ef4367e0932dbe7265d876bd95880808.1765956025.git.zhengqi.arch@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4dd1fb48ef4367e0932dbe7265d876bd95880808.1765956025.git.zhengqi.arch@bytedance.com> X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: D8E3A140013 X-Stat-Signature: 31b7n9h3uhxxxh7uc1y14nyydssz4byf X-Rspam-User: X-HE-Tag: 1766010083-353377 X-HE-Meta: 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 D/eGawvj teSj5/VQveQj7NuKplpPVMjTm5FhVqvi7WTgKw/mRSuXaIGeqlsRVNSu8K6qSJQo/m+iQKrsCGP6/4QYBmEzyFwfA1QsvLQZQ3/rGXzmllQX2Z3eHnueBEJIyl7+VgEtTvQKivXzkN07EBW9E11M3Aoh1BS/BCey8wXIRgGfBOMtCxbQhwBv1XpXh8IU8g6oJKkOb1c6ghGJki5OBs4wXgMbXvdb04B/GRM8ZAArXxOF9BOUL1iaurn39J9Kmrxd3XlxYAweMUchCyO5c9I9r+QmJBIut7UrzCuwGL+cizMNWFGjpH4AaMxYJRjOuLx8Bm61OyxePVqtLzRdfg7l54hnTsfJpORBoTgSu59Au6IsK4V21K6y88plguQ3ZdPyD90U2MnUBn/bZFuYPLgLfxXq82vf/pJyO16TIOpAvluNsnXl8I5QOX1K42ys70Ep+0vrO4o9K2DBX3yl1yMArYqpjWo7+rd2P1dZjOtolaA/uD8jS6h8FawCdb0FfYQ0fqzLO3XdFqcf6dDi61I+kUHlC/vpsUJdquDrPtrLHKobWuVA= 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 03:27:39PM +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 mem_cgroup_swap_full(). > > 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