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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 13/28] mm: migrate: prevent memory cgroup release in folio_migrate_mapping() Message-ID: <4icfifjfr77f4yle5cn4buotiscvpwxccxerwuzuj227l5kqs2@bdkeysc6xigp> 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-Migadu-Flow: FLOW_OUT X-Stat-Signature: 91btz8oarrn13xft67ey5uijh886fijd X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 7A5851A0003 X-HE-Tag: 1766188301-270728 X-HE-Meta: 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 j1N1sZln q4avN3lnwy1izNrkmTlUsX3q4UNq0sGuje1EsS5OEpcPY/ixmIbuNoiD0RtphAHylw0fqzSCiswLEiUwqC526uBvOieGgF9RjnNKeBAOmkCMP6o50btOjp9O/mi59Z6SmDoMyejhEELLPExrSKU8Lnr8TbRXt+UPsxXNRzokP9dnGaAbBaDJmHw3IFSOesoqGcVBFMy2A9GstjUcH324s3xKWEX3IfsfRHm+OTQAJnOWEjgIzctBjlvNpzuMq2bYDaqWloZCmLTM35OKzUk6ov6nqezAKCLL5boqhS3+Ic8E8kpBqzqKgHxRJXL5rzemSg9yiB+aVS2FbBmg= 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: Shakeel Butt