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b=S+pDJMhXziAJr/dUnXYVT+7qiwwywkY5CGkhjVrlnbONIgUSo6UIBB7n874AHlQgI CrlPMffuYtVHmc5Fdunv3viqL9xchhv9+KmM+9nGgzzWm/SCmvIzIaYr2r+CsTAGq4 HBupKmHMUR3DAXVWOqHmJK8HYr8SL4TqUUmWpKzY= Date: Sat, 21 Mar 2026 10:40:21 -0700 From: Andrew Morton To: Gregory Price Cc: linux-mm@kvack.org, vishal.l.verma@intel.com, dave.jiang@intel.com, david@kernel.org, osalvador@suse.de, dan.j.williams@intel.com, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-kernel@vger.kernel.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH 0/8] dax/kmem: atomic whole-device hotplug via sysfs Message-Id: <20260321104021.4a6074330131a2058e8706bd@linux-foundation.org> In-Reply-To: <20260321150404.3288786-1-gourry@gourry.net> References: <20260321150404.3288786-1-gourry@gourry.net> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: F394AC0004 X-Stat-Signature: wjykr4pq84aao3863dmdbhndaeaat1sd X-Rspam-User: X-HE-Tag: 1774114823-657514 X-HE-Meta: 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 nPmiJa/t 2L6daVJdsK4HkODgiwFg8T0tpBmMG07imNuJcwEhxdHhjgVtpXiegUX05qOMtWzt1Jr22/edFle/4TFSeQuXA9PKf3xQX+K4AiyD0vgWy7vPhSmURW9KHbJQ3UbQh78GKV252lWnaJNqS9gc7sykREeWHHTQl286cjtcXIUb9QfbAn3aiCUP+c+nSlW3904PMRvvqjzy3yvvKCzEPJASHNwNIKnyjW7j8//2jD/6hmoU0fL2Q81oeP0vjCLFFy2H3UFX6g0f8yZo/n+L9gCJj+pa5aheK3QvHDC/C8c2aJfcSmSO+cMm4GHvEpzRBPzb4Xhn/z15Z5Fx6Rj9N8/9PK9qV8Fw4HfimmpGvt8jMRDYmErCb5anLMNXV/Kjzam7zEASM16x15KLYfbvlQ5eZQsN0PpKR72YvrHHf Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, 21 Mar 2026 11:03:56 -0400 Gregory Price wrote: > The dax kmem driver currently onlines memory during probe using the > system default policy, with no way to control or query the region state > at runtime - other than by inspecting the state of individual blocks. > > Offlining and removing an entire region requires operating on individual > memory blocks, creating race conditions where external entities can > interfere between the offline and remove steps. > > The problem was discussed specifically in the LPC2025 device memory > sessions - https://lpc.events/event/19/contributions/2016/ - where > it was discussed how the non-atomic interface for dax hotplug is causing > issues in some distributions which have competing userland controllers > that interfere with each other. > > This series adds a sysfs "hotplug" attribute for atomic whole-device > hotplug control, along with the mm and dax plumbing to support it. AI review (which hasn't completed at this time) has a lot to say: https://sashiko.dev/#/patchset/20260321150404.3288786-1-gourry@gourry.net