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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 07/28] mm: memcontrol: return root object cgroup for root memory cgroup Message-ID: References: <3e454b151f3926dbd67d5df6dc2b129edd927101.1765956025.git.zhengqi.arch@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3e454b151f3926dbd67d5df6dc2b129edd927101.1765956025.git.zhengqi.arch@bytedance.com> X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: E7CDF40010 X-Stat-Signature: qr74hhduhcxx3rypsdgj47uaoad3e6jr X-HE-Tag: 1766104796-639520 X-HE-Meta: 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 AoiZ5hQ3 0rUJc1dacZrahR5IPLkUSZ0xyIQIA6JFQkawZGMyo0a4BpsnbpQhRv/zc4LF4bUBw4IXvT57X4fkHOPGTTJfhmx56U6J/bfnLt3XXwF/hMVq7FG/22wOGptkzEdr5FxdjvFNO17vJGVVyBjNIg0JNlfz4QqbmaeyGHHHKkPPxmGxjHhLk/5nPfvKsq70YoqJSKnuqHrG4+tZHatiVAgyXVZ40eLf8PVsfTUUbP2TpXLAM43q/4HeYJnlKsImDUtVjuNUhKcnau5T36HI= 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 03:27:31PM +0800, Qi Zheng wrote: > From: Muchun Song > > Memory cgroup functions such as get_mem_cgroup_from_folio() and > get_mem_cgroup_from_mm() return a valid memory cgroup pointer, > even for the root memory cgroup. In contrast, the situation for > object cgroups has been different. > > Previously, the root object cgroup couldn't be returned because > it didn't exist. Now that a valid root object cgroup exists, for > the sake of consistency, it's necessary to align the behavior of > object-cgroup-related operations with that of memory cgroup APIs. > > Signed-off-by: Muchun Song > Signed-off-by: Qi Zheng Acked-by: Shakeel Butt