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Tue, 16 Jun 2026 06:44:55 -0700 (PDT) Date: Tue, 16 Jun 2026 09:44:53 -0400 From: Gregory Price To: "David Hildenbrand (Arm)" Cc: Waiman Long , Farhad Alemi , Andrew Morton , Farhad Alemi , Yury Norov , Joshua Hahn , Zi Yan , Matthew Brost , Rakie Kim , Byungchul Park , Ying Huang , Alistair Popple , Rasmus Villemoes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] cgroup/cpuset: rebind mm mempolicy to effective_mems, not mems_allowed Message-ID: References: <8d3b4561-92cd-4ebc-8462-5fb0fd659e8a@kernel.org> <70f486ce-5ef6-4d72-8cc3-7086f4eea930@redhat.com> <51eafe6c-6622-479b-b391-6d3ff9350e75@kernel.org> 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: <51eafe6c-6622-479b-b391-6d3ff9350e75@kernel.org> On Tue, Jun 16, 2026 at 08:59:07AM +0200, David Hildenbrand (Arm) wrote: > On 6/16/26 05:43, Waiman Long wrote: > > On 6/15/26 10:26 PM, Waiman Long wrote: > >> > >> > >> The reason why I am suggesting to use cs->effective_mems to keep the old > >> cgroup v1 behavior. If the consensus is to use the output of > >> guarantee_online_mems() for mpol_rebind_mm(), I will not be against that but > >> it will be a slight change in user-visible behavior. I'm not grok'ing what is user-visible here. The two values should effectively be equivalent because we're using this value to constrain mpol's during a hotplug event. If the values differed, you would be saying there's a race condition that could affect correctness of the rebind (which can't happen, because this whole thing is done under the hotplug lock btw). Can you help me understand? ~Gregory