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[173.79.60.52]) by smtp.gmail.com with ESMTPSA id af79cd13be357-930f68d5d6dsm171863585a.20.2026.07.22.07.04.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Jul 2026 07:04:55 -0700 (PDT) Date: Wed, 22 Jul 2026 10:04:49 -0400 From: Gregory Price To: linux-mm@kvack.org Cc: Zhigang.Luo@amd.com, arun.george@samsung.com, balbirs@nvidia.com, brendan.jackman@linux.dev, yuzenghui@huawei.com, apopple@nvidia.com, alucerop@amd.com, matthew.brost@intel.com, akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, corbet@lwn.net, skhan@linuxfoundation.org, gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, djbw@kernel.org, vishal.l.verma@intel.com, dave.jiang@intel.com, alison.schofield@intel.com, osandov@osandov.com, jannh@google.com, pfalcato@suse.de, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, pbonzini@redhat.com, osalvador@suse.de, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, kasong@tencent.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, yury.norov@gmail.com, linux@rasmusvillemoes.dk, longman@redhat.com, ridong.chen@linux.dev, tj@kernel.org, mkoutny@suse.com, sj@kernel.org, jgg@ziepe.ca, jhubbard@nvidia.com, peterx@redhat.com, baolin.wang@linux.alibaba.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, lance.yang@linux.dev, usama.arif@linux.dev, xu.xin16@zte.com.cn, chengming.zhou@linux.dev, roman.gushchin@linux.dev, muchun.song@linux.dev, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, driver-core@lists.linux.dev, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, linux-debuggers@vger.kernel.org, linux-fsdevel@vger.kernel.org, kvm@vger.kernel.org, cgroups@vger.kernel.org, damon@lists.linux.dev, linux-kselftest@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH v5 28/36] mm: add NODE_PRIVATE_CAP_HOTUNPLUG for opted-in private nodes Message-ID: References: <20260720193431.3841992-1-gourry@gourry.net> <20260720193431.3841992-29-gourry@gourry.net> Precedence: bulk X-Mailing-List: linux-kernel@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: <20260720193431.3841992-29-gourry@gourry.net> On Mon, Jul 20, 2026 at 03:34:22PM -0400, Gregory Price wrote: > Add CAP_HOTUNPLUG, which allows memory_hotplug to migrate a private > node's folios for the purpose of hotunplugging memory. > > Without this, hotunplug fails if any folio on the node is allocated. > > Add node_allows_hotunplug() - which returns true for any normal node > and private nodes with CAP_HOTUNPLUG. > > Signed-off-by: Gregory Price after this question: https://lore.kernel.org/linux-mm/al-pkvmgIxGu3LzM@gourry-fedora-PF4VCD3F/T/#m5b8166212a276fece2380f2dd03d6864375a576b and some off-list feedback about limiting initial cap bits to active use cases, I realized that this CAP bit can be entirely eliminated. hotplug notifier callbacks already allow a driver to prevent memory block state transitions - so that control already exists. v6 will remove both the filtering here and the cap bit. ~Gregory