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([2601:188:c100:5710:627d:9ff:fe85:9ade]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6e8f401d4bcsm395776d6.124.2025.03.05.08.27.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 05 Mar 2025 08:27:34 -0800 (PST) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: <9c24f14f-c7a8-490e-9077-0d977d175d89@redhat.com> Date: Wed, 5 Mar 2025 11:27:33 -0500 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 4/9] cgroup: Print warning when /proc/cgroups is read on v2-only system To: =?UTF-8?Q?Michal_Koutn=C3=BD?= , Tejun Heo Cc: cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Josef Bacik , Jens Axboe , Johannes Weiner References: <20250304153801.597907-1-mkoutny@suse.com> <20250304153801.597907-5-mkoutny@suse.com> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 3/5/25 5:17 AM, Michal Koutný wrote: > On Tue, Mar 04, 2025 at 06:55:02AM -1000, Tejun Heo wrote: >> I'm hoping that we could deprecate /proc/cgroups entirely. Maybe we can just >> warn whenever the file is accessed? > I added the guard with legacy systems (i.e. make this backportable) in > mind which start with no cgroupfs mounted at all and until they decide > to continue either v1 or v2 way, looking at /proc/cgroups is fine. > It should warn users that look at /proc/cgroups in cases when it bears > no valid information. I like the idea of warning users about using /etc/cgroups if no v1 filesystem is mounted. It makes sense to make it backportable to older kernel. We can always add a follow-up patch later to always warn about it. Acked-by: Waiman Long