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[109.81.93.164]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47d7f661a03sm117662475e9.13.2026.01.07.09.17.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 Jan 2026 09:17:31 -0800 (PST) Date: Wed, 7 Jan 2026 18:17:30 +0100 From: Michal Hocko To: Hannes Reinecke Cc: Gregory Price , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, david@redhat.com, osalvador@suse.de, gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com Subject: Re: [RFC PATCH] memory,memory_hotplug: allow restricting memory blocks to zone movable Message-ID: References: <20260105203611.4079743-1-gourry@gourry.net> <88dbe97c-3510-4ce7-ae85-067243a152bd@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <88dbe97c-3510-4ce7-ae85-067243a152bd@suse.de> X-Stat-Signature: kzk6c7w9picncyewxiiq8c88xk8dznof X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: BCEE9100004 X-Rspam-User: X-HE-Tag: 1767806253-184901 X-HE-Meta: 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 2rOxcWkH xe0GA6ushIPoBMX/uBdbwyLg40FLWpdwqMm0xAZiRgUrH3NQXLf6hk0q4C87GfYSlqcf76YWrRglAGe59o7jHDdlCiUWMnSP0YEyeKDinOC1Lu5HZC3S3sogKV94RXUctlD99XfaxxV4rRLhVsXThdAVvWLitzkSm4mdXEQlo40/Q49EjzGxxEfJbZ6cG7mALRZ1xGkubyMs7qeHMNh2pU0rn5M2GQT2oH8wC+Eok+CHEJqGJun5Uh6DdPEGVrarbQq99irVdfHr0othp5iP/etG2/efxq3hvkAchvbVdtfzOMZTiHqdVRsj/e5h40JAuy6kKTf1uyGY7ee0bTCPHdcqZUjj7fPqsIGyhkCnFdvHRpH0+ng5asela4UpGw2YDVbYBpsZ+rq7PqkNZv/ezUxnRjQ== 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 Wed 07-01-26 13:47:41, Hannes Reinecke wrote: > On 1/6/26 20:49, Michal Hocko wrote: > > On Tue 06-01-26 11:53:30, Gregory Price wrote: > > > On Tue, Jan 06, 2026 at 04:05:48PM +0100, Michal Hocko wrote: > > > > On Mon 05-01-26 15:36:11, Gregory Price wrote: > > > > > It was reported (LPC 2025) that userland services which monitor memory > > > > > blocks can cause hot-unplug to fail permanently. > > > > > > > > > > This can occur when drivers attempt to hot-remove memory in two phases > > > > > (offline, remove), while a userland service detects the memory offline > > > > > and re-onlines the memory into a zone which may prevent removal. > > > > > > > > Are there more details about this? > > > > > > The details are with Hannes, I was just recapping what was described in > > > his devmem talk at LPC ("To online or not online"). > > > > I know of policies to online newly added memory blocks but I am not > > aware of policies to re-online something that has been made offline. > It's not a policy per-se, but rather a udev rule (which one could > argue _is_ a policy, mind). There is a rather long-running SLES bug > around this if you are interested... I am aware of udev rules which automatically online memory that is hot added. But I am not aware of any rules to re-online memory that has been offlined. The former makes some sense while the latter makes very little sense to me. -- Michal Hocko SUSE Labs