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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> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3e454b151f3926dbd67d5df6dc2b129edd927101.1765956025.git.zhengqi.arch@bytedance.com> 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