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Thu, 18 Dec 2025 05:45:49 -0800 (PST) Received: from localhost ([2603:7000:c01:2716:929a:4aff:fe16:c778]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4f35fd60192sm15091761cf.19.2025.12.18.05.45.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Dec 2025 05:45:48 -0800 (PST) Date: Thu, 18 Dec 2025 08:45:44 -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, Qi Zheng Subject: Re: [PATCH v2 26/28] mm: memcontrol: refactor memcg_reparent_objcgs() Message-ID: References: <8e4dff3139390fc0f18546a770d2b35c9c148b8b.1765956026.git.zhengqi.arch@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8e4dff3139390fc0f18546a770d2b35c9c148b8b.1765956026.git.zhengqi.arch@bytedance.com> X-Rspam-User: X-Rspamd-Queue-Id: 461881A000C X-Rspamd-Server: rspam10 X-Stat-Signature: qnum13uf6p9xhf6qf3fby7rbzthd3xke X-HE-Tag: 1766065550-483653 X-HE-Meta: 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 E7lO9Pug 4g9nZwTkIWvrbu38C62KNgrPKkazTVAF/CcJ5At+F/hooCoTvx0/w0jXOAOtNNFBIoyolWaUvzOpnViHmStsIzFSBCxRMGRr6gVGyaBzck307q5oBSz6oBplB43bWN6yiWVDPcs+5EpeEXdFuskZ8btpX7Y+2uH0OA1MlTfG+tJalGmTLABJzNpAuANnljfg0OQYPzs6l7QwvUJLTHrOrjSQw5AFLqGIugf41HX7xRyIm4x5exezSLJPGHYk1eAWA/13lUeg08Vu0gbFPc4HKsDO6WmNvo0m0WBi2AUYp6WM2OI2zL6IGpaR+T+q6Q+0srlFIFXX8du8iKXAWi8qnInlJkR2jLJy1F6uzpAa8o7VtlYXVHRx19s9s/ESk1npz2xVrd3QTcX7nfO/Ny8lCBLtir9s3nPcjDjTcAg6T6JrHJB/6X+45OBzxBLA2Wp3ENWda7jfR5gq0ldCCOyftu+RBLNu0WYVqEr1B 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 03:27:50PM +0800, Qi Zheng wrote: > +static void memcg_reparent_objcgs(struct mem_cgroup *src) > +{ > + struct obj_cgroup *objcg = rcu_dereference_protected(src->objcg, true); > + struct mem_cgroup *dst = parent_mem_cgroup(src); > + > + reparent_locks(src, dst); > + > + __memcg_reparent_objcgs(src, dst); Please have __memcg_reparent_objcgs() return the dead objcg for the percpu_ref_kill(), instead of doing the deref twice. And please use @child, @parent (or @memcg, @parent) throughout instead of @src and @dst. > + > + reparent_unlocks(src, dst); > > percpu_ref_kill(&objcg->refcnt); With that, Acked-by: Johannes Weiner