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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 09/28] buffer: prevent memory cgroup release in folio_alloc_buffers() Message-ID: <63h3n6m5ek623nzq4pwkwkhu72jqjjastxgnsjuvrvwpevv57v@2ki32ihzx7lj> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Queue-Id: C64BB80008 X-Rspamd-Server: rspam10 X-Stat-Signature: 4tzyzkdi47jphqt4m9hyynb768d8md9h X-HE-Tag: 1766110478-492967 X-HE-Meta: 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 AL2FDOu4 Ao6cZLqoMBf54PBzkIaNeNmaoiixfVhiUypqAmYAxXrcsqYOR+gqdHpWQ/AWIj1ktacGUt+zloDxlu1Cawq24moxaQGhR5I4NRYKoxGYv+6vrwIls8VROujsIPe1eDphz1dBG+OP2sc2Ffs+oxHMmWDtP7tvwFZFS1nXwIUH5tjNimP/SqtbwlIFTp+x3eebQY0EKK3unOqIZc49Y0h1/Jz/DiVWazw0YW7zxDCNERADzTqGiq1J+TY/BiLF29uqud+5kpCnuP5F22+1AkwBfq7SUfIYXPl+nXUcIf7Q17HG8QS7Ehm5yqVsRVt9MYXEnSFnrlcFhk27vy9k= 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: Shakeel Butt