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Wed, 1 Jul 2026 08:32:54 +0000 (UTC) X-FDA: 84939542268.18.764E1F2 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf11.hostedemail.com (Postfix) with ESMTP id 851CA40006 for ; Wed, 1 Jul 2026 08:32:52 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="ej/bhLV2"; spf=pass (imf11.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1782894772; b=Cac+Kr/Mb//BO4BMJDl5wvHMBdLVfm+NCBpdJvB2ui2JsEN6zj/EczGmQ1eyi5eZQrhwMh nQz70kVQGSvIn8lmxUVyr+NDHd6TOP9k576OFa5i58kbdyIgV3hK75OEuj3Ae31OjZ4ld+ rsypgpG1U0G7PRAa3wqkiEuXNh2635M= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1782894772; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; 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b=ej/bhLV2lC+xeGIQFxa6NbBX1bHdqFNVtfWMnPmcd3tYv3DiL3LK7f2SwmyHZrZem l1q8F5oRB3cekt4CRrVDQIfP7q7Iov3PkmuyUSHpSKlltbx8Da2dndhdKb1ngitM4Q C329B8cViplBVPzYmkkhMZEYcXhFm7rhGjuTImwRJ3abixHDXV0TaEoBkUeESuu702 NVFshKGSoc5Ux1bfta221QCZaPqbE8ZUibY6RO+yOcflQe8JjVfD3bo+rL1WnPF1XA J2Zvrr90sP9a9KZvZPY3HHIj9zx0gEHnw4wenBVPv7HeFeQUZjPbHC4von+mCgp4au 3UZEX/6wxZPFw== Message-ID: Date: Wed, 1 Jul 2026 10:32:44 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 06/10] mm/memory_hotplug: add offline_and_remove_memory_ranges() To: Gregory Price , linux-mm@kvack.org Cc: nvdimm@lists.linux.dev, linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, driver-core@lists.linux.dev, linux-kselftest@vger.kernel.org, kernel-team@meta.com, osalvador@suse.de, 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, akpm@linux-foundation.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, shuah@kernel.org, iweiny@kernel.org, Smita.KoralahalliChannabasappa@amd.com, apopple@nvidia.com References: <20260630211842.2252800-1-gourry@gourry.net> <20260630211842.2252800-7-gourry@gourry.net> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 851CA40006 X-Stat-Signature: oec545y11awdyy9y36rffkknp1emqbbo X-HE-Tag: 1782894772-737791 X-HE-Meta: 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 4ZCAJF5W 3xerRhrqfh7mJPKux2JkzOiSoVnsBvTDcC5NfaxwcGGBbCplVqiDPtlAtq7TbmC11+G4eW8nXMiTC67B1JWfz6aCchTIFDPBEMmrmRV8EPq1v5EkDUsgVIFkeYpg2ipBWaGLR3/YV8SDUte218dPiok4Mda6L2fXTPXVd+MQ2kEP96ghDlrgopr2DLXuQ2y5zUGeeGCVRFoMtM+XHUFKJ0QhI9Q1qBZihqeIBl3UFzwHfB19V/qpAeb8bcL8zaeo3vMJzrK4XWY9PAJiuZ3KHoTotGCmv8dMsm4blc41V7OpU9ot2evvHVKI9n/LyNmUKdPXnMopd2Lxs8OjIE7UUUbS+EUZPm8+nVPJb/3B9S/ciGD+IqyN0Tt3fUFdmM0tedZxvSMizFa8CxNU= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/30/26 23:18, Gregory Price wrote: > offline_and_remove_memory() handles a single contiguous range. > > Callers that manage a device composed of several ranges (dax/kmem) > currently have to call it in a loop, which gives up atomicity. > > In addition to pushing rollback logic into the driver, the lack > of atomicity creates a race condition between system daemons trying > to manage the same resource: > > - Manager 1: Offlines memory blocks. Removes device. > ^^^^ > - Manager 2: Detects offline memory blocks, re-onlines them. > > Add offline_and_remove_memory_ranges(), which takes an array of ranges > and processes them as one operation under a single lock_device_hotplug(): > > - Phase 1 offlines every block of every range. > - Phase 2 removes the ranges only if all ranges are offline. > - If any offline fails, the whole operation is reverted. > > This gives callers all-or-nothing semantics for the offline step, so a > failed or interrupted unplug leaves the device in a consistent state. > > This also resolves the battling managers race - the second manager's > operation simply fails when the block is destroyed / cannot be onlined. > > offline_and_remove_memory() becomes a thin wrapper that passes its single > range to the new helper, so the offline/rollback logic lives in one place. > > Suggested-by: David Hildenbrand (Arm) > Signed-off-by: Gregory Price > --- Acked-by: David Hildenbrand (Arm) -- Cheers, David