From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from DM5PR21CU001.outbound.protection.outlook.com (mail-centralusazon11011056.outbound.protection.outlook.com [52.101.62.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 581AA29D291 for ; Thu, 9 Apr 2026 17:34:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.62.56 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775756045; cv=fail; b=AcSk3KFa1shdFx4Wx6Ha311nTioF803f5RiOmLy6jLGFrjHoMss6byBKBGj/EPcefBHCLY3DpO6Zh89yVP1v97RzSdDsshpfambvR46lvokw7WGwGOvZqzhi2JNjDn/ojafblnHqVT+0T3MPEEybHm/SfTth964gLjoWqDrtFSs= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775756045; c=relaxed/simple; bh=JCT4CE2DbjIQjTKRTZw0BieD0HUYD7ay3+jCsU9I4uw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: Content-Type:MIME-Version; b=obVU2uEJA5LqlWsSLaHVYod6fFKvKhpm4xo8TCjAzeTPfc8u+RVfQnc16i2zrm7WcVweJ7ZFbZ2514/sRJakRkLG17E3Loq7GJvZEu/AZSIJOTWthJo1Qz1o51IzA9x2GfB4JYO0fFluFh+uvPj7UWJ+ERzDNvvnv5OX+w1ZZm4= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com; spf=fail smtp.mailfrom=nvidia.com; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b=kRHyD9iw; arc=fail smtp.client-ip=52.101.62.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=nvidia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b="kRHyD9iw" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=rNDJAQk2Nx8ZkfUVRKficFdcVuzpFE7rVW8gPDXKnY2KiGTj4vHIbA6IgqlIWk8X6co6LOsxe+iwd9bDJXWnp3J/d/nUvrEMsiEz7n5Lrc+rqvUlNMeEt272CFPcN3oSyradaez5+adZss+f8V13ukTjP2G1K9cJNlHtG/3PYTNHlTdSxuCizS/6N/+IPolp5o04hmLCwynbodK7BL5HgpBA0cZRN57ePrFab7StXr9KOJyIpbyNSfLlBq243g/9fCC4n6q+vmg2SmL1ff/KXqDmXrEDOOqkcAB/FuUof+MNkvV1UB8ncgQZQo25PUfNkUA8EDNF8CWnu8Y7IrohcQ== 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=JCT4CE2DbjIQjTKRTZw0BieD0HUYD7ay3+jCsU9I4uw=; b=VwmnL6f6G74HL+2pvvoyDM5+Af0vLt0YtXL89ungRXwy7FjQZ3F3QisZalK60Yg8yb5UDcFCUcjBIS7uM/sLXIbCpNMEyR6+Z5W0pa0iQnzpdDD2lISLcF8+LngMDtizE0vIJtroBJYc1wuAxZrOecxTxfwruIHi3Qjp+fpLMIt3ZiBwhJDYgZzzxsPwWyTjV3GXl6LWL0blZG/mZk277CLaN8JZP408XGfUdwCLpgzSVo7X/uXDdD1W3qXGOCwjr5fnOlprKueEK+6OArNUgA9vVMB6bETugmVjZu6i5ageuFa2pugmWuMedOo1AqD/nx79Az4ZSWhlEmdI9zK6Og== 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=JCT4CE2DbjIQjTKRTZw0BieD0HUYD7ay3+jCsU9I4uw=; b=kRHyD9iwf+S7x0fuWJ6Z/KCVDrMTVFry/DE92wZ40irh+OR56WaZ4NOE+tV7xvIGr5d5/iSCdsujUXBC0c0d0yb3mjR5vmjXzHMVcV1Ww4UP5FsUaj0+7I9nE+zdlks1Bk6GA7bZ3Ch+hgyC4lMmj5g3EIm0wyUHGk/OjF4kQRfdb8sWsXHHKJe9rzCEXxtsLrdg0U+qYZADdw0hh3HLRrh9pvQ2WCSUqok7ddAcHeikw1zc2QehGelXAV1h8ACM3CnDKs5BhPRXF9fAPxH3XjaEnvhjyZVA+ew2ZGEMmXlRsPb7ISKnlKBPDvmmfAV+03AzNJJ0ixOEF5F205MOww== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from DS7PR12MB9473.namprd12.prod.outlook.com (2603:10b6:8:252::5) by DS4PR12MB9561.namprd12.prod.outlook.com (2603:10b6:8:282::9) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9769.20; Thu, 9 Apr 2026 17:33:54 +0000 Received: from DS7PR12MB9473.namprd12.prod.outlook.com ([fe80::f01d:73d2:2dda:c7b2]) by DS7PR12MB9473.namprd12.prod.outlook.com ([fe80::f01d:73d2:2dda:c7b2%4]) with mapi id 15.20.9769.014; Thu, 9 Apr 2026 17:33:52 +0000 From: Zi Yan To: "David Hildenbrand (Arm)" Cc: John Hubbard , Andrew Morton , Jason Gunthorpe , Peter Xu , Mike Rapoport , LKML , linux-mm@kvack.org, Sourab Gupta , "Matthew Wilcox (Oracle)" Subject: Re: [PATCH] mm/gup: fix GUP-fast fallback for NULL-mapping order-0 folios Date: Thu, 09 Apr 2026 13:33:48 -0400 X-Mailer: MailMate (2.0r6290) Message-ID: In-Reply-To: <794e7270-c91d-42eb-b2a6-67929198a1da@kernel.org> References: <20260409014647.397515-1-jhubbard@nvidia.com> <4d6c1af0-dee5-4f1b-b74c-2ebc23de7baf@kernel.org> <1A7433E5-C8C1-45EC-A0B7-2BDC7D065B1A@nvidia.com> <794e7270-c91d-42eb-b2a6-67929198a1da@kernel.org> Content-Type: text/plain X-ClientProxiedBy: BL1PR13CA0142.namprd13.prod.outlook.com (2603:10b6:208:2bb::27) To DS7PR12MB9473.namprd12.prod.outlook.com (2603:10b6:8:252::5) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS7PR12MB9473:EE_|DS4PR12MB9561:EE_ X-MS-Office365-Filtering-Correlation-Id: 78d5e973-6e2c-4a87-6c65-08de965e2aa8 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014|22082099003|56012099003|18002099003; X-Microsoft-Antispam-Message-Info: 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 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)(1800799024)(366016)(376014)(22082099003)(56012099003)(18002099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?Rv594WJT8Lc7OgW8jWkiTs+EXuqVDFH/DqtK/Bk7oXNlcK9ULB6oahArm7b2?= =?us-ascii?Q?EFyDLnHblUi+SiQVWUCduxvNbyFAr3MGLk/pOX9iDLG7YwR10rnbPENy2Qqr?= =?us-ascii?Q?mG05oZyxePcvKzcS3vMeglps3DYcjGlGe28aznUv1ym7RVDpvQYJl6JURTbw?= =?us-ascii?Q?jrUmq/rZS3fj0ExGq6aciwDrBCkDq7wVaaV4Tu0CHnE/cIcQTI+LcubQbUOq?= =?us-ascii?Q?mbVbB1s44kURLlEgfAEqwtyXmmhvIJwf/gsbsKMxXaVRz3KPychHDnS5OcQB?= =?us-ascii?Q?EQcbVwdw9yPm+g3YWZtMqjV2Yffhx9QPNhiG3h212rqTTsNoqt8axPtSDs4r?= =?us-ascii?Q?nlFzYThB9S7m1X8kzc9r9nf2zagBu+dFRPe8t8A8dyx+uOW2kYCV5fHHz7ze?= =?us-ascii?Q?LhYXf4FN8TQlP8LeGoLYEffufmfzjP6jD7agCFLCwHOA31QbyqbNjI83MyU/?= =?us-ascii?Q?ULok9TbmHRV0ihwXUzeAcDDKJknYeF+awOcanebWSfr2wFmsh5ZbBxprslOC?= =?us-ascii?Q?uCJ2PjDbcEhcOzC0+PWsGR377PvdvRuwtQN3fmFZfISlc/DqFZnxnfz767AR?= =?us-ascii?Q?HsG27LA4geydGRD5IRuLDkR7cTSwjJwIBpd7xkAnSny1/8UJ7UyU1NudAlMh?= =?us-ascii?Q?7gSSfMTrBg4vp+UqmlaTfWLUWMDRmLYy5Pm1Gj7FYjjZfBomuDBB0pZIKhR8?= =?us-ascii?Q?4HU6TSq3+Tksw3rEEUS4krPjIg4AOPAcJSVGRUCZP1Gzb/pkVpDqsivv81/g?= =?us-ascii?Q?7qSxwAlE1pbVfjpCN574pzvzzV+5wljA5WD7Jf238QLWSTBSULQ+mmuGoeAw?= =?us-ascii?Q?iRoKl15R8WS9bJ+LK+wz5H7ITdppmX0LyAf9P/5OnrvbUjbl5efmsVjkr2WP?= =?us-ascii?Q?A4JUX5CjPvOWgEpr2nB/7OOcn9eTQyvcSLO/lf9UG2Rqp8x/cHdH6qpIg5Sl?= =?us-ascii?Q?yXQgwbo7tQzD0U5Mm3Gw8FagytPxu7HFA732Lms9NSBsdn/k9SpuTbzrXLJj?= =?us-ascii?Q?dJAbXdb9WKTkOBeE1VWTY3Ewf1jpV5v1zcGsznhqQPA1l5TSoqmxpjBNW2o5?= =?us-ascii?Q?/pOihztXlmc5KOUuWMHXOVppc70AxkBOuw7YLmtI5SxcMkdzEpB6B3jz5PGT?= =?us-ascii?Q?YGzz7GkKW2+nKtg1kJqwuVx2JNjK4Ev7B09KxLPBGa+qslWzwbGthYfyP6U8?= =?us-ascii?Q?NTWyO9PEvsXwSWrMW93RgMF5QPsfR7wuZ1N7zNWpTISJSEDW+IHfbhIwUKlN?= =?us-ascii?Q?1qy/Ms0Css2E34uLNHXtSzIkVPrDpgMaoAiBfgEjJPeHe/uYGjaT98DSXGZR?= =?us-ascii?Q?FJTubbLp29tDEG7inERKApfnDqvwEMLXL0bKMjYQBsKroUSakpxSQh196OC0?= =?us-ascii?Q?9b+EUBaBezE9nHWLLrd7GRGC8bHuBdVMjs9nsVQnoepIJGq/3MdQnrcaAU2R?= =?us-ascii?Q?V1i8FoPFBRBn6V6UI3XZ4dm0Nd1wxphjuT5uZ9i5zSq1njnK7+FfErq4iGvE?= =?us-ascii?Q?K2cen1HGphTaCQsBA6KG7t9WdXIKlcBJXwkd2ZXaAdpd2QIe6+4FqtBMRstU?= =?us-ascii?Q?JwSBHIWQ2s78drmEeOOD+/hW73cTIpDGUah68rPuRcFicl/Gbe5pE8gB6HR/?= =?us-ascii?Q?H36UiD/Au2Xu6JIzWNwSC4FSQOk4uJg7ZoEQYQze1Z/LCHtqwWEJFhNyvyyr?= =?us-ascii?Q?DDbhT9xDTBH5suCk9tIfQ1PYxkBrVrj5y3ey3rbupNgpvauWyVhyEJGCf+U7?= =?us-ascii?Q?G+LdrdLfkg=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 78d5e973-6e2c-4a87-6c65-08de965e2aa8 X-MS-Exchange-CrossTenant-AuthSource: DS7PR12MB9473.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Apr 2026 17:33:52.1606 (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: of+BQSxCPqNTt0siNIbZU8AiAjon6b2u25RW6OC9pt1E0vWeFkjjNET55ayuwBDG X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS4PR12MB9561 On 9 Apr 2026, at 13:31, David Hildenbrand (Arm) wrote: > On 4/9/26 18:55, Zi Yan wrote: >> On 9 Apr 2026, at 11:11, David Hildenbrand (Arm) wrote: >> >>> On 4/9/26 17:05, Zi Yan wrote: >>>> >>>> >>>> The idea is to give every allocated page a NotRmappable page_type and >>>> 1) let page_rmappable_folio() remove the page_type by setting mapcount >>>> to 0, since page_type overlaps with mapcount; >>>> 2) allow callers of alloc_page*() to change page_type from NotRmappable >>>> to other types. >>> >>> Could we instead just set the special type in vm_insert_page(), after >>> verifying that it does not have any other type? >> >> You mean in validate_page_before_insert() we set the page to NotRmappable >> if it can be inserted, then in the rmap code we reject NotRmappable >> page/folios? And NotRmappable will remain until the page/folio is freed. >> That should work. So the purpose is to avoid setting the page_type if >> a page/folio is never going through vm_insert_page()? > > Yes, only these non-folio pages will show up process page tables. > > We would add a safety check that the mapcount really is 0 (-1) or > already the proper type (NotRmappable). > > Rmap code would then simply skip any such thing. OK, I can give this a try in my new version. Best Regards, Yan, Zi