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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 12/28] mm: page_io: prevent memory cgroup release in page_io module Message-ID: <2vypu4pg3mfhmwyhwmlzozhdnjw4xne62sxe5hpqdohm3s2bjz@sk53oaivblz4> 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-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Queue-Id: AA72D40007 X-Rspamd-Server: rspam04 X-Stat-Signature: tuxwqmcw5ur8yr1nhhq9sta5ofnd6dt3 X-HE-Tag: 1766187858-33201 X-HE-Meta: U2FsdGVkX1+Mk1BYEi8WaQtxBlmxYSoFgZnQBfLNvXY8KeXlviduQ3fj4bPdYuVsILMGy6N0rljr2m182Fw2v9bJbXv+t/+bDiCFtN7vUF6W3lRCvoo8Nr224YuNYm0KNPkZZrsoUIWATAmLwWwV0aOfejGSsw1ZASsJulerZckpQ2/iODtpqFqW/LibvbXEl6tLMkALBSn5zjkuyZzPfFx3kSMTBmiHwlXmP4LYkEjN8RrTYMrA2Mu4Hxrumn5tm8H9ZOsJrzAHG65QTO4tTX5Bj6YOi3k4GjO7zVE2fxbPYqeq6hgLBvUnblgx10iF8m1F90UcOl6oddv1EnOybGC+P+r7vynpYeT/tgTZlY4Oge8NLcsmdVFSss5qR0C7TSfDXSk+FPSe4z0tz4oLAukCi30u38SzC54o8lmkjsbWPoP6HPq+la2GLxfL7S6D5u8afOwqG7T6JbwY5m4EnWNCOikkA+dOSsKatKKiKxDnfWevP+fJ+ghjl744GzaKEf5Nuc7VbrfXXBtLCOM/7crDFrmNdlGlVGoMfIJKQZoEoxw5SRcE+b+zbmFQQPD2ssz8TSG0aLybej9weZ6Kf7PtXW6jYn5yG7lqhACYHCjIK87Kqu7bWOO/c46iBl9bRH9IR6Lqk5wfxrSHrgKR9UDkECx4aZT1ZCALUCj3jwDnBvAhVjbslTEzyGkELKqMXHwUR6fyI0WEsCJB1PnZUh6flZRwsfg5iy5FmMiGXxSWZhEt3nBnyMnpfFFgWOI2YR4yK4Zc2qe/61MGi8AL3Gib5NE2JXheWvBC3xe17NamtlS/vKKeIXwJd2aXcJVwRYbXRtkw7B8GBZVGMMHa7R5EjJPIdFJepU1fJ27KFtDu5lrNTFaIFO7Mcb92/bY/KwaRq2IAvj+RwKx66LOz3fIH7jo5DFHdvE3wOD/wrqwUDdcjR/j9phCfHZpnvSwiw2aqwRctEindJEe6Zwb oraIAVFS YdXQOwQLjbU8NvWNFqgC4RvyTsJJKIYjNg86YMqn1qy0myacY5MG1Jp6o/90zVRmw8C2o3HCWayBywSzFgq/m+h/SVYD4qheTwbksV/6PtsgSlYs5W6b7V+ttRlaISuPLmJ2E0twkLD97CWjmxg9Rgtq0yUSrjtvFrt6xrGQ6cxk80MUTNZg+J1RTt3yE6HMsXy9M91RzMUChSKbxm2NHfgnqAADKyFwz3UQvvwul8gYX9mpCSC1xBGdli9PwuEdpwwqEGC5AH3Dx8Ofq7EFP7iH6lP6nG70UycBLJCMoaCU3tW/CBL3hvoR+qSwgDU/ZIpANtccMAsmVOoQ= 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: Shakeel Butt