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Wed, 17 Dec 2025 13:28:15 -0800 (PST) Received: from localhost ([2603:7000:c01:2716:929a:4aff:fe16:c778]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4f360751619sm1247261cf.12.2025.12.17.13.28.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Dec 2025 13:28:15 -0800 (PST) Date: Wed, 17 Dec 2025 16:28:14 -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 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-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 3BB3214000D X-Stat-Signature: uxrxc51g1cg9fkgmfpn3jqakuc6158u1 X-Rspam-User: X-HE-Tag: 1766006897-909326 X-HE-Meta: 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 VuUZIPgL RIZYlBsIOptSLQXTqRLFQByRocfGFxu8bUydZrMqToQmZMjwt87Vf68R2CIZ7Pboet1IBlURiXfGGC2T6zuM6Jdz5axcZFNxdLgLzUUtfXlltE4PA151neRfjYM6MINaTl6q/FEcIWa93ARh4+pJp4jR8s7ky2V44GqSodqzOepZVWzTaIm7AqHD3Wtwlm1ziZlcebsAbjxfskP+Hx6RMK6Mjbmn0wyzmRJRQa8HfiH8wClJUo2lHKUyAZzlrTK6ItzNDJgAUt/t5QobPthT9GDOpnCqT8eRdF8jGnO09syFpznOXri7tHVOgekZsomTlCyx998E6sZLQKRIiKoPXAMPSGZ8MxHyeZZEweABCejdLzE8cW/YZCM+W/BEcyKbpL7eEeecyA9jy0I/Jh/FmnD4upadcYtJxmLqXzRjAVVnFDDk090HdJumFN/NljXHVuf/FfEGJqLJzv4o= 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: Johannes Weiner