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Thu, 17 Apr 2025 07:35:12 -0700 (PDT) Date: Thu, 17 Apr 2025 10:35:12 -0400 From: Johannes Weiner To: Muchun Song Cc: mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, akpm@linux-foundation.org, david@fromorbit.com, zhengqi.arch@bytedance.com, yosry.ahmed@linux.dev, nphamcs@gmail.com, chengming.zhou@linux.dev, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, hamzamahfooz@linux.microsoft.com, apais@linux.microsoft.com Subject: Re: [PATCH RFC 01/28] mm: memcontrol: remove dead code of checking parent memory cgroup Message-ID: <20250417143512.GD780688@cmpxchg.org> References: <20250415024532.26632-1-songmuchun@bytedance.com> <20250415024532.26632-2-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250415024532.26632-2-songmuchun@bytedance.com> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: A5B7DA000C X-Stat-Signature: osnkrfsz5er8q45n4ry4itkyjxihx1xo X-HE-Tag: 1744900514-426054 X-HE-Meta: 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 kQaPmTJI /jkjws842a6fuyn5oUYq17KSXBLsZDkQE2+pFLmyNbnOjnC8IvT2bfkyysbRFmQVAcGrnTgWRGJ7Hv5CdRYO4yYIQvMQNjIQENslQMempj4HXw92FEibSozb9nUyL3n2rwt544gjWXPKPOM1IyCahQBTfuS9oEJePuEmyLhZbK1A4GeCRZ53apjoEzal4AZE44F9VDZ22UvFx/ZDkfYgKgBE8MOPq9Bm4OJkMgBOooS0mk2CYddC7IHb8zXRE8mSxVjYDvyYengON/CqfFZG7MEfbgB5hWj5e1iXB19hr5lwCKMzOcfdhCaScZXPe5TWpLA0+PsdIhs8heyfYIumq7J0QlSJW8COs6TeRwuP1G8/XgrmJ3UiwyMwzn5W0dNqzDkgbmvu2H2uVtH5pFJVZw02F4Y7iy7MI1upi/xhnjoSNDgY019iN36Qt+Hcw91UkMr1NrUZSvSI63xvH1uQGMuT5ippGXP8sFzx1V+hheErfLtrMP5vBE0kpB5iBt2/JDugE 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 Tue, Apr 15, 2025 at 10:45:05AM +0800, Muchun Song wrote: > Since the no-hierarchy mode has been deprecated after the commit: > > commit bef8620cd8e0 ("mm: memcg: deprecate the non-hierarchical mode"). > > As a result, parent_mem_cgroup() will not return NULL except when passing > the root memcg, and the root memcg cannot be offline. Hence, it's safe to > remove the check on the returned value of parent_mem_cgroup(). Remove the > corresponding dead code. > > Signed-off-by: Muchun Song > Acked-by: Roman Gushchin Acked-by: Johannes Weiner