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b=JWHfN6sZ4I/IFdbxgUMDIi1ZsXpD6lo5RKB9Asc7gBYUpffn7mj/hMe1QiMo1nZPi BTFmc5g2XPj+sJ4zBgbi8mo088EUEM0hd4z2oDGSGfT7yedN2NC60vsDRsfOJFHEX4 h+sXrfhpL3OdA6P8R+QfCrmPZgw9uRBwcVdwfyiqlJW1b0oCBK8jHAADoCf4U/XKLV 6yqIy1ABBfGrhNFlHR51sfhJGYVQp1bx+wvvEmseglnQT1LzcV4xFHckU0OJHvyIB8 ZfSENUetO1gNmIBXtqatNymJ2zU3McgW/yzyBzXMoicmGfzfvati/ictoZqEimj2o5 yVI87RgFYODsg== Date: Sat, 19 Jul 2025 06:18:48 -1000 From: Tejun Heo To: Michal =?iso-8859-1?Q?Koutn=FD?= Cc: Ben Hutchings , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Zefan Li , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Chen Ridong , 1108294@bugs.debian.org Subject: Re: [PATCH 4/4] cgroup: Do not report unavailable v1 controllers in /proc/cgroups Message-ID: References: <20240909163223.3693529-1-mkoutny@suse.com> <20240909163223.3693529-5-mkoutny@suse.com> <7sbzasggfk3elhvxsd5mtuzd4yo3c64wuzkaulr7yqybpfxwuh@g6dcatriw7hx> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <7sbzasggfk3elhvxsd5mtuzd4yo3c64wuzkaulr7yqybpfxwuh@g6dcatriw7hx> X-Rspamd-Queue-Id: 2B44340004 X-Rspam-User: X-Rspamd-Server: rspam09 X-Stat-Signature: fqm7b6fs7m63roxd3d4u87xzkw4rywr1 X-HE-Tag: 1752941930-25124 X-HE-Meta: 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 B8Tg5msA nSDGs24NWpD8KzeOQzljuQ2yhqcPuTFEKoQQIpN2t5dq2v3RnaUWCXuMvaEI01NpakiTW3Pi/kL3kFr4L+qDBeHsKpryQQaJ1kPzRCA7k67AM0fyCV3Nbqn9zw5UoGDUstFTZuiT6Ld75d6/6KoBVO34+nuHcXQVZ/xgsK8Qt21iO9jyAb/sHeT9KudH2/9LFhOWjWp0RZfAbYysHFUsLyrGJaFpeTNB5A46fZTMbvWb+g/2dqyIXZT/2w95kuRABXGN7xPs9PsgXzIuIebYoWcFNlcRFAomkV80mI+mSR2+Tnemg/hmoeO4Pz1UFk28EBEfcuJ0fe0ARa86C5Nz9stdu0Alv1/BB7rauoFsd4F4cuXYeLLtX7521Fj18c/7kTT26 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 Fri, Jul 18, 2025 at 11:18:54AM +0200, Michal Koutný wrote: > From ace88e9e3a77ff3fe86aee4b7a5866b3bfd2df58 Mon Sep 17 00:00:00 2001 > From: =?UTF-8?q?Michal=20Koutn=C3=BD?= > Date: Thu, 17 Jul 2025 17:38:47 +0200 > Subject: [PATCH] cgroup: Add compatibility option for content of /proc/cgroups > MIME-Version: 1.0 > Content-Type: text/plain; charset=UTF-8 > Content-Transfer-Encoding: 8bit > > /proc/cgroups lists only v1 controllers by default, however, this is > only enforced since the commit af000ce85293b ("cgroup: Do not report > unavailable v1 controllers in /proc/cgroups") and there is software in > the wild that uses content of /proc/cgroups to decide on availability of > v2 (sic) controllers. > > Add a boottime param that can bring back the previous behavior for > setups where the check in the software cannot be changed and it causes > e.g. unintended OOMs. > > Also, this patch takes out cgrp_v1_visible from cgroup1_subsys_absent() > guard since it's only important to check which hierarchy (v1 vs v2) the > subsys is attached to. This has no effect on the printed message but > the code is cleaner since cgrp_v1_visible is really about mounted > hierarchies, not the content of /proc/cgroups. > > Link: https://lore.kernel.org/r/b26b60b7d0d2a5ecfd2f3c45f95f32922ed24686.camel@decadent.org.uk > Fixes: af000ce85293b ("cgroup: Do not report unavailable v1 controllers in /proc/cgroups") > Fixes: a0ab1453226d8 ("cgroup: Print message when /proc/cgroups is read on v2-only system") > Signed-off-by: Michal Koutný Applied to cgroup/for-6.17. Thanks. -- tejun