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emacs 28.2 From: Alistair Popple To: John Hubbard Cc: Matthew Wilcox , linux-mm@kvack.org, Andrew Morton , Ralph Campbell , nouveau@lists.freedesktop.org, stable@vger.kernel.org Subject: Re: [PATCH] mm: Take a page reference when removing device exclusive entries Date: Thu, 30 Mar 2023 11:55:45 +1100 In-reply-to: <87zg7vt75v.fsf@nvidia.com> Message-ID: <87v8ijt5pk.fsf@nvidia.com> Content-Type: text/plain X-ClientProxiedBy: BYAPR03CA0018.namprd03.prod.outlook.com (2603:10b6:a02:a8::31) To BYAPR12MB3176.namprd12.prod.outlook.com (2603:10b6:a03:134::26) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BYAPR12MB3176:EE_|CY5PR12MB6527:EE_ X-MS-Office365-Filtering-Correlation-Id: 0f888547-2570-452d-4129-08db30b9f6b6 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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:BYAPR12MB3176.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230028)(4636009)(39860400002)(346002)(376002)(136003)(396003)(366004)(451199021)(41300700001)(66946007)(66556008)(4326008)(66476007)(2906002)(4744005)(36756003)(83380400001)(38100700002)(5660300002)(86362001)(186003)(2616005)(8676002)(8936002)(6862004)(54906003)(6666004)(478600001)(6636002)(37006003)(6512007)(6486002)(53546011)(6506007)(316002)(26005);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?tKspFu/wS6J0ztaVi9USrRaOOb2oqgPNRzmTx8qq2JrL1CemcEA+6h8Zou/k?= =?us-ascii?Q?nz+DN16PJxv9qKEw8W92A4QXuA/8JjQuzUPcRUkeDc1QFkBlMwSbSFBbAMd3?= =?us-ascii?Q?0AClZI9GNjd5mMKxU1npOlvw8bbKXoxOBaSs88mrJ+tW9wEhNCp+yNjZfiXM?= =?us-ascii?Q?URLupS7kv09U3GlyCNcjW1yZ3qmIiLktsCfz57lkkKxx5+A2cWvTyot6ynAP?= =?us-ascii?Q?GtOPWtUqWM+HlZDWTlX644jlITc+cuXitC9TnSX9l735vd3CbNVq83QdpnnU?= =?us-ascii?Q?QUGFdKemkyTTaKkn7TjvPxZpjK20sLsHH75mt5Wjw+SdN+A4ChnMim6Uytaf?= =?us-ascii?Q?37dTPlyaajHGy6DX6ChusmMZ903rgwicTqIafhjLPpR+lLaAAY/GjEnSPEMQ?= =?us-ascii?Q?CaT2RPp7eJsx+KY334v7yk3EB90NbP+n2ebUmW7jWf7PqmCWQiXpfli6LQsJ?= =?us-ascii?Q?9jDhnfo3Fy3jPn5M9Kp7DqJIAnSGOWmGVIPn149G+3KQWJm3DEOcv3OixZTb?= =?us-ascii?Q?O9tqzdNSsiVqjamQ/UHbPHMNm5cF2foFhRBkVR+zODj9BxnvMWX9xmP9aSZ3?= =?us-ascii?Q?JC249sE2AMT/I4gMq0XHZodwYqwFam/7QAgzoLUJOP7l4wfXhKkSw0xy1x+o?= =?us-ascii?Q?oCWB0gBEnyilr3pCmeEX6oPSbZolepAewQ2FRHpVaVrEtIFvYYZKA1YF7TXs?= =?us-ascii?Q?NB07h7kCClXJPNeens3VnoxiHa1ImmpZY6Os4ARNk+VdHNXASf5PvMTert3R?= =?us-ascii?Q?yFM1zhE7ALDUqgVIg3ZwxHNRBJeqzqCX1R8RAPrgTT0j5z3OkIydnS6fCH0J?= =?us-ascii?Q?gPHJcYtNNICjrajl8Q99zCA5s1apkAbcFTSv4Xl/3jVWYmkGXk26WmdGH/0t?= =?us-ascii?Q?IoSCZYxNoWYFx2n4OcXHzgrL3cfgUUPIJOuuRuzqes2lD6DcZHmDpPCPM5Ct?= =?us-ascii?Q?MK0dqMUtlDAwtb90SrZkpioOWT0VNMKVe1UfZ+DgRfLpDPO49af2r7qreFem?= =?us-ascii?Q?HUqXPFudN04/I6HpTpZXJJZYLLF+OTyeF7KwhZYA/XnbfYZv1ybnl/wDn3w7?= =?us-ascii?Q?d8pglESMKPd4RtAtwRhvIDX5+Bh5hbjazyUL0tmTiB5X2YuY/NyJlpsBiuWl?= =?us-ascii?Q?NiOzTuVI/vATrgfalB0nS6G7/+23RExHaBjL1iUm1N9dMzoRzNcWOb2FFVyz?= =?us-ascii?Q?bDuBA94ggkSV8CgkZb8IM4DerqNvAcbzvVgrdEKW76B8bKG+j6l5b6tVKwNI?= =?us-ascii?Q?cfcFi8DinxELVpm0DqHYsgUSYAzfqhUsovYexUj/RYr+Yc/UDubGgyxUxvLG?= =?us-ascii?Q?lRNCXtaCvPpf51PF+Plc5zMvOZREL9tEdW63KPTLwYeI3N+CB5J+Vaf2l0OR?= =?us-ascii?Q?qpFQSIpuje6mTnNhXlFs1O0DxbwHXCojKSj4GNwFIZBv6DrDnn6XswZEICxd?= =?us-ascii?Q?yjjzSRuR6thMNaXwMl9EB4VFH42jMk49OBVgry06G+wE0OpxjZLy3mt8hxzf?= =?us-ascii?Q?S+lV+Bw22NSfF7jSZBq7fg66lRyj56IN6HDs/Ty/Od8bkurvbLp1ex71U7Kk?= =?us-ascii?Q?shkSOsjnpjeJ3vepgwyNwqbZcqB4xgVkmUcnbp44?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 0f888547-2570-452d-4129-08db30b9f6b6 X-MS-Exchange-CrossTenant-AuthSource: BYAPR12MB3176.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Mar 2023 00:59:07.0861 (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: v6CPIc6GA8LSt3wOpBlJjtJw++jAnMHH029JBQb8LxTnU801K/zjudktHCnAgZXWYlvfYmP97iv3TgC4xSnL9g== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY5PR12MB6527 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org Alistair Popple writes: > John Hubbard writes: > >> On 3/28/23 20:16, Matthew Wilcox wrote: >> ... >>>> + if (!get_page_unless_zero(vmf->page)) >>>> + return 0; >>> From a folio point of view: what the hell are you doing here? Tail >>> pages don't have individual refcounts; all the refcounts are actually > > I had stuck with using the page because none of this stuff (yet) > supports compound pages anyway so we shouldn't see a tail page > anyway. But point taken, I admit I need to find some time to get a > deeper internalised understanding of folios than just s/page/folio. And looking at this while updating it made the mixed usage of page/folio look really werid/wrong so thanks for pointing that out. Will send an update. 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>>> From a folio point of view: what the hell are you doing here? Tail >>> pages don't have individual refcounts; all the refcounts are actually > > I had stuck with using the page because none of this stuff (yet) > supports compound pages anyway so we shouldn't see a tail page > anyway. But point taken, I admit I need to find some time to get a > deeper internalised understanding of folios than just s/page/folio. And looking at this while updating it made the mixed usage of page/folio look really werid/wrong so thanks for pointing that out. Will send an update.