From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7AF03CCD183 for ; Mon, 13 Oct 2025 17:15:31 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D5C368E006A; Mon, 13 Oct 2025 13:15:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D34268E0009; Mon, 13 Oct 2025 13:15:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C49878E006A; Mon, 13 Oct 2025 13:15:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id B1ABF8E0009 for ; Mon, 13 Oct 2025 13:15:30 -0400 (EDT) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 5A426BA2DC for ; Mon, 13 Oct 2025 17:15:30 +0000 (UTC) X-FDA: 83993742420.06.5508F41 Received: from CY3PR05CU001.outbound.protection.outlook.com (mail-westcentralusazon11013036.outbound.protection.outlook.com [40.93.201.36]) by imf25.hostedemail.com (Postfix) with ESMTP id 6F6D9A0007 for ; Mon, 13 Oct 2025 17:15:27 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=uYSB+nEz; dmarc=pass (policy=reject) header.from=nvidia.com; spf=pass (imf25.hostedemail.com: domain of ziy@nvidia.com designates 40.93.201.36 as permitted sender) smtp.mailfrom=ziy@nvidia.com; arc=pass ("microsoft.com:s=arcselector10001:i=1") ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1760375727; 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; bh=j3JBMtlszUbxeUQ0kxc80ynHD3M85r/QMLxvbfhZxvo=; b=gSbeHdn6qlsU9GP+LDDYeCCPO9a79vFAnXZEyT9pOWqIGjEonXyxov6gzPaZNtbfcw3w/S T0LUJzqWeMWOwJ6iJCdrkIS09P/F9+vtmljl1+nJ6/yhjdgj5YTaFapwWxfoH1MsmdRT4T LFKYn9f9iO+Lq6jwGZEiI8SfcyU1fxs= ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1760375727; a=rsa-sha256; cv=pass; b=hxHqeSuyYkfJlaZGmaliC1rZI6kDVxhIYrYmUZmyo7aEYcQrlrZT9erPnC0yOsGLGLFXKN m2ZZ3uCzwWTCZdCTc1lPbI1f4sKi3LU9+pYmCf9YTQgkvAiUltdMvTTrMEu2ifdlY7zObX ITDjBJntzdzrcADt3qqe79xJj06vkz8= ARC-Authentication-Results: i=2; imf25.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=uYSB+nEz; dmarc=pass (policy=reject) header.from=nvidia.com; spf=pass (imf25.hostedemail.com: domain of ziy@nvidia.com designates 40.93.201.36 as permitted sender) smtp.mailfrom=ziy@nvidia.com; arc=pass ("microsoft.com:s=arcselector10001:i=1") ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=wWL6uuu1IglSPGVze//WaNMRJsAJhoeqLnGI6I8OOfel0nO+WHDcLiXXy1wNlNRrY9XdBrQlY0SWUKtT8EeTovX0S8OMU/uGbdObsqWIlr1YYcOAoZT1xHpcxrW6K441xuTTkiOeQorgTAqEpZecv4v7Wcryu5+/PYOYV1Z2+MxwhiRhfcfAvLH5MJVmVyIJWjPc2Pu6OCumFvO5LSnIET1r5HTzohf/WnPEB/rUmnr/fl05R1E6BMTfUrrOnm8k/5uRyTrH5IRxi3kAD4EzC7SzWtcaC2QD+xhAWwdo2JVf9CEutjOe3oOmmubl/yfG2dW2vjURC6vNV0j6xxgC6g== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=j3JBMtlszUbxeUQ0kxc80ynHD3M85r/QMLxvbfhZxvo=; b=HQxw1cU8fepGJsKM8Slkt6+Ai40bbplHJIUlV0JjX/ZjOsR728WYturssjjnKIQFZBEWeOai3RJ5WC7hX0FOqeAdwB7gSUuYKOgnlnHTYhenxFSV7fMd5UO9P/e6Nem3+xxafWYD9I5PI3y8inCYFGMOuMz1IXVDUHGn6MC7uyB8kn8iVnoa3JGNnaT5bEK141AYJSO2oauqHJQOyivt9X1tRDxbJVYtfLMf3zyzHpgT911sUEdPovNH6mgQ8vteouneLLA86rsgfNJXISyH8IbpIWfKXZlEsT77iqpglDfQzpWZfgdEwzsztu+ry/lHQMkT/S1991gM/pqx/OpfQg== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=j3JBMtlszUbxeUQ0kxc80ynHD3M85r/QMLxvbfhZxvo=; b=uYSB+nEzftFugLpQPWxyQgBCyVgikNc5rbP38RGvEYIMYLkhyJ8E0Qz8lnbHU3/4W1ik9nvaoCuDZFeZobJ9v6e2dP3xSqiPKT/mS4Wb7P/Ai43zQviumKIRy8O+rYVfNrzlzDrqhGfsJWafKfOjz4QQ2fO0hihw5vunfkPYAiGjBw/mLTNrraKaspiNyavsDzILj+l/aKvHBVuAYXlsCAH0AFieXPbBRUbvw77AA3czp0otKfQ3EovP3ucj0edgpKyoShDVkPszRPLu1h5FTsXJwr+Uf9AJXJH7sGq0ZZk0tAISurHwbRIQIwovG+pITDT1g1tZ95Bor0R6rGpqbg== Received: from DS7PR12MB9473.namprd12.prod.outlook.com (2603:10b6:8:252::5) by DS0PR12MB9037.namprd12.prod.outlook.com (2603:10b6:8:f1::13) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9203.13; Mon, 13 Oct 2025 17:15:23 +0000 Received: from DS7PR12MB9473.namprd12.prod.outlook.com ([fe80::5189:ecec:d84a:133a]) by DS7PR12MB9473.namprd12.prod.outlook.com ([fe80::5189:ecec:d84a:133a%5]) with mapi id 15.20.9203.009; Mon, 13 Oct 2025 17:15:23 +0000 From: Zi Yan To: Qiuxu Zhuo Cc: akpm@linux-foundation.org, david@redhat.com, lorenzo.stoakes@oracle.com, linmiaohe@huawei.com, tony.luck@intel.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, nao.horiguchi@gmail.com, farrah.chen@intel.com, jiaqiyan@google.com, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/1] mm: prevent poison consumption when splitting THP Date: Mon, 13 Oct 2025 13:15:18 -0400 X-Mailer: MailMate (2.0r6272) Message-ID: <0ABAE11C-1DF4-4E76-AEE5-CE5E8ADFDC15@nvidia.com> In-Reply-To: <20251011075520.320862-1-qiuxu.zhuo@intel.com> References: <20250928032842.1399147-1-qiuxu.zhuo@intel.com> <20251011075520.320862-1-qiuxu.zhuo@intel.com> Content-Type: text/plain Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: BN8PR15CA0016.namprd15.prod.outlook.com (2603:10b6:408:c0::29) To DS7PR12MB9473.namprd12.prod.outlook.com (2603:10b6:8:252::5) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS7PR12MB9473:EE_|DS0PR12MB9037:EE_ X-MS-Office365-Filtering-Correlation-Id: 4f175468-41b7-4241-2797-08de0a7c1800 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|366016|1800799024; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?MCKL1XwaKgxH3tTue8D0w2Wc+xH8fmlv+p5IvjTujOZSWdoKxuiF9KUWVcTM?= =?us-ascii?Q?nF4X4yYP3eXmIpnr7L21Mie1Q38wzYRvGr0t/Vo68C5grHSE2e2mAbK/84eB?= =?us-ascii?Q?4KpKo1nYwRwMI69ceTka9UUBDbrBuPFwOq1rvnYCtRyb7KmlsvqJhr0ItDWl?= =?us-ascii?Q?00f/RZVdITImimQ1y2asbT3RQf7Qg2a0yB/43t0/epsJzKDyTrRmA7K1Dqp2?= =?us-ascii?Q?BI0suymIiw/CROmZGZ1hYbH2Ld6t7ncP1YNd4iKnP+9kUa2jOA3/kUd3XHH2?= =?us-ascii?Q?QuLBSlkRtw3jhP0FxHtwL3uHDX5M6TY/vZWgPBlDson5w+38urevVtHCX2rF?= =?us-ascii?Q?fR015JSOiXMCWewu5cZBbLJtW+YlA6+eYUkWvIRE8Opln/Et4Zqwq5QCr8rT?= =?us-ascii?Q?V1++PklBcyYsloeFkqXjHTtimmNQAq8R4vMBIrx4VOh2P6gFUoN2/EyWe+dG?= =?us-ascii?Q?FsqhGO1c6v/JMHXxheDyZ+2WeQTuof4S/AxDfEyRarmkpFrdUXVtBqXBLj09?= =?us-ascii?Q?aLOrmCi9zrae2olVzC9HWRWasZjTkRHf0m7m5sxb/axiwHl/C98fHIrEi29U?= =?us-ascii?Q?5b1gPGgqJXjQ1vFayTrFWogGtuMKzudzdLBxU9q/5R2D426pF0mrvUiuujeD?= =?us-ascii?Q?h8r6xuxgmAOFDw7c3kEPvW7A6/v/vAknRBJY5dp3Wopi1PnuVE4cOm08qRaQ?= =?us-ascii?Q?LgkkpVl3roPAR34eSqe4WW33GNhuqowByv2TIpkxQSD72RGTzWjc2aOZwgKA?= =?us-ascii?Q?6922NJpu9Of0A2//5UtAFEZolcF4mtGXT/R7F9b4kBSlLhiL3kqN52wNkAmq?= =?us-ascii?Q?luY//1JzCbDoDBZmD/2udTlglrJfhisCMfKK5aP1w5cCtLIokKtSazRKoGW1?= =?us-ascii?Q?Kupzq1Np4+kbCibp1gIAf4ZHYeaJ82dA7j8c/PoZVfES2C9Ga0uKThTlLgDm?= =?us-ascii?Q?KsaHi34bjpw+QDBx/PQZ5U4wKHEp0eh7+7NhkrVmdH/Rm4d7uqfERcejV+8w?= =?us-ascii?Q?PXH3+98lWiXuC6xSTHnZUBZlmnwd1k5RoQxcTxfN/6T9U9+sXgiAGw9nhLd8?= =?us-ascii?Q?zHIhEi8wGDOdatwRUgUphnV3+mebfqhDGKw4fDlLD83IzAYyQaW21Ub8lZms?= =?us-ascii?Q?3s285FrF9BsEzEQIcuf7gc/vORsEgxPBoRCUXVvQ18ccppOkI5NQgt1tNVHo?= =?us-ascii?Q?bBGOVXjeDC3lsxMCFEwTWCIoc5N9UiWY03H/Zcim7EAlIUz5ke3qaDAp1fVR?= =?us-ascii?Q?es21I5rZoBTAB8qBt+FcY1OM9MV7WzuxrCTk3Dl0gMvZWfp0y8LzhtuZxBzk?= =?us-ascii?Q?ptXfn/iqpgrSU2xwUMi/MhubpQcNuZsn6hAbLE2ZjOychHQH4QN+qu+j5vdv?= =?us-ascii?Q?B9Mam2YFUNO56SsAxvkOQrTqP3mjv1eGVq6/SQNc56lf4a7kTiaCNPape6Ow?= =?us-ascii?Q?gJaZWxR7vEggLg27iGkRGUcPiBvpLA2e?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DS7PR12MB9473.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(376014)(7416014)(366016)(1800799024);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?EeaksIezRB9yWwURrDguih2wFZlWU49Rl+Rl+bDlGRiIqFyW8ag6rql5YA5e?= =?us-ascii?Q?8SzL0c8RdRAWJ3Pr1o9M9KMY/O6AIGjSWl9cSjjuHuLXZizoJbyawoPXFwRD?= =?us-ascii?Q?Nbs5sCd5ylg/+gwipsGlosPKMZk4eyD3QJrGLl+a81sqczVu9EZWlputriZz?= =?us-ascii?Q?0/KOXed84mxWxQJoeZsBD9TQu6j/+KWa4sIRgWN/sd1gixpcM2RDQU8thz+Z?= =?us-ascii?Q?1t0PcS1bknufiZqMr54dTvG8zq/S7Hj5isvUzbVKP/Fhop9kJXXWzRH7mSPL?= =?us-ascii?Q?oDRfyGjVSjAanR3QTk/GWf69s0dA51z7fiVpVNqt/21iqjhHYn45deoROMRb?= =?us-ascii?Q?nCAv3L+nUaa9s/pDgkSK7ngFML6IMrrmf5Cxgx+iVzt9rsUI06DWDa43WQ/i?= =?us-ascii?Q?BvNc7olCUYLO+1VHnlASvQOdDzj6Q2MaGtewt/xhv7YbgaHQCpWOmGCb1GPM?= =?us-ascii?Q?yZ6K79rCOx3xp828NHX0R6oQ+Tmsc2zkjIiSgpBblI9T35subTw3D3RiZnN1?= =?us-ascii?Q?2KPf2EMcekFPm92UrW+9R9IIbwstLidXCt4mfcEx63Zukj/YZajIr1Dcyusl?= =?us-ascii?Q?6sa01vkP2zIsJIPDhGeNuHruQo2vOmMRPxlyMcxvW5GnelZ0uoFHzEmcciYI?= =?us-ascii?Q?F37UqWoSTL3s86vu2D8+yWHbK+l2A6PWuyK25r1ZzSUivWue5N1ajDYkXqcS?= =?us-ascii?Q?P8D27Vn7hmTVSVE+kfbHPF1z9s0gMkQa5H95uI7Eg2n/HI9JslcYZx5kV+gC?= =?us-ascii?Q?lKE26elDqEHSTpQ0x33N84CRx0LrR83kHpi18uMNpXbngVdHXqBaPHDEhf+I?= =?us-ascii?Q?xRLRXv+GrtcFY3yK7ARgqUe+PoBXz/xQj9QSV+sT6VNUSgheuOIf0L38j0iY?= =?us-ascii?Q?wdw4/5K8VHhzRov/lathD5WrT2fWW+hqPDvpTvHpPGwTuVDGJQNTTPYhpLrk?= =?us-ascii?Q?XRF3p+3K/auGTSkVUaoTuH14JE6Vj89Q2mMoJFNE7G06xA9d8Wd5quy0igqf?= =?us-ascii?Q?hm/K9RgicAO9yTKVg65+akl/qg940mB39YkBxw+XHv9ONIJGfWd/WilGmv6U?= =?us-ascii?Q?AMV+uf9PSnlGCkOfPiNAJr7zk9qu6dtN9CuGmFLe6SS064Nqi1Ivbdj1Cndi?= =?us-ascii?Q?zZa1qPDiP5tg98t+eBwWBxoWZOGjGkr1cbgVM9bBgavS/NukjdNGCQvRn/jm?= =?us-ascii?Q?Vw0QFihMwYOdbYXcDmcWCoC/uhqtM41WJZd3J0IMXThgEuleP58AhISvLFr2?= =?us-ascii?Q?dQEg0Nn79ftjaPcAyKBSy342BcsRJUoyVBzsPl/IloIjEzyYHvk38NekuUF1?= =?us-ascii?Q?ZYOI4BgL06G4IL+9wbicgO8CLOhYfeeZ/4zYSsb/lvMHP3nP9Wj/rRbc4TjP?= =?us-ascii?Q?Q7S6/e4IPa48RV603lFoqK/xlqyuEb0qcACRJXqBO/q5z4GS1MaQNVByqeuF?= =?us-ascii?Q?A1IHzBCIeLyQbbXkFStJZ9lsMLRkT0phMQQcE+5B3eyg6w+xsqjlozTHapMf?= =?us-ascii?Q?6H8V+hXhU2L5CDDyuxDvFFhtue7RT9tXSBKflYsCgViXHAOy+lA4rTimXoSw?= =?us-ascii?Q?2Q1DPupdKrLFcJNmqMGkyms3kmb8bj3TNTvSUC5h?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 4f175468-41b7-4241-2797-08de0a7c1800 X-MS-Exchange-CrossTenant-AuthSource: DS7PR12MB9473.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Oct 2025 17:15:22.9711 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: qsFRdzyrS4w3OZe6KlHRMDhd6Zge+mL15CbGFgbSgBb7L1YMv57HcT0A8XBhR3xN X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR12MB9037 X-Rspamd-Server: rspam01 X-Stat-Signature: 9m8i5yjbn7pr7pmm17ssahdj8okgkud8 X-Rspam-User: X-Rspamd-Queue-Id: 6F6D9A0007 X-HE-Tag: 1760375727-682255 X-HE-Meta: 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 wfDJVgjE 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 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 11 Oct 2025, at 3:55, Qiuxu Zhuo wrote: > When performing memory error injection on a THP (Transparent Huge Page)= > mapped to userspace on an x86 server, the kernel panics with the follow= ing > trace. The expected behavior is to terminate the affected process inste= ad > of panicking the kernel, as the x86 Machine Check code can recover from= an > in-userspace #MC. > > mce: [Hardware Error]: CPU 0: Machine Check Exception: f Bank 3: bd80= 000000070134 > mce: [Hardware Error]: RIP 10: {memchr_inv+0x4c/0xf= 0} > mce: [Hardware Error]: TSC afff7bbff88a ADDR 1d301b000 MISC 80 PPIN 1= e741e77539027db > mce: [Hardware Error]: PROCESSOR 0:d06d0 TIME 1758093249 SOCKET 0 API= C 0 microcode 80000320 > mce: [Hardware Error]: Run the above through 'mcelog --ascii' > mce: [Hardware Error]: Machine check: Data load in unrecoverable area= of kernel > Kernel panic - not syncing: Fatal local machine check > > The root cause of this panic is that handling a memory failure triggere= d by > an in-userspace #MC necessitates splitting the THP. The splitting proce= ss > employs a mechanism, implemented in try_to_map_unused_to_zeropage(), wh= ich > reads the sub-pages of the THP to identify zero-filled pages. However, > reading the sub-pages results in a second in-kernel #MC, occurring befo= re > the initial memory_failure() completes, ultimately leading to a kernel > panic. See the kernel panic call trace on the two #MCs. > > First Machine Check occurs // [1] > memory_failure() // [2] > try_to_split_thp_page() > split_huge_page() > split_huge_page_to_list_to_order() > __folio_split() // [3] > remap_page() > remove_migration_ptes() > remove_migration_pte() > try_to_map_unused_to_zeropage() // [4] > memchr_inv() // [5] > Second Machine Check occurs // [6] > Kernel panic > > [1] Triggered by accessing a hardware-poisoned THP in userspace, which = is > typically recoverable by terminating the affected process. > > [2] Call folio_set_has_hwpoisoned() before try_to_split_thp_page(). > > [3] Pass the RMP_USE_SHARED_ZEROPAGE remap flag to remap_page(). > > [4] Try to map the unused THP to zeropage. > > [5] Re-access sub-pages of the hw-poisoned THP in the kernel. > > [6] Triggered in-kernel, leading to a panic kernel. > > In Step[2], memory_failure() sets the poisoned flag on the sub-page of = the > THP by TestSetPageHWPoison() before calling try_to_split_thp_page(). > > As suggested by David Hildenbrand, fix this panic by not accessing to t= he > poisoned sub-page of the THP during zeropage identification, while > continuing to scan unaffected sub-pages of the THP for possible zeropag= e > mapping. This prevents a second in-kernel #MC that would cause kernel > panic in Step[4]. > > [ Credits to Andrew Zaborowski for his > original fix that prevents passing the RMP_USE_SHARED_ZEROPAGE flag > to remap_page() in Step[3] if the THP has the has_hwpoisoned flag set= , > avoiding access to the entire THP for zero-page identification. ] > > Reported-by: Farrah Chen > Suggested-by: David Hildenbrand > Tested-by: Farrah Chen > Tested-by: Qiuxu Zhuo > Signed-off-by: Qiuxu Zhuo > --- > v1 -> v2: > - Apply David Hildenbrand's fix suggestion. > > - Update the commit message to reflect the new fix. > > - Add David Hildenbrand's "Suggested-by:" tag. > > - Remove Andrew Zaborowski's SoB but add credits to him in the commit= message. > [ I cannot reach him to get his SoB for the completely rewritten co= mmit > message and new fix approach. ] > > mm/huge_memory.c | 3 +++ > mm/migrate.c | 3 ++- > 2 files changed, 5 insertions(+), 1 deletion(-) > LGTM. Acked-by: Zi Yan -- Best Regards, Yan, Zi