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To: Christoph Hellwig Cc: David Hildenbrand , David Howells , "Kirill A. Shutemov" , willy@infradead.org, linux-mm@kvack.org, Jens Axboe , linux-block@vger.kernel.org References: <939183.1743762009@warthog.procyon.org.uk> <67d4486b-658e-4f3f-9a67-8785616e6905@redhat.com> Content-Language: en-US From: John Hubbard In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BYAPR05CA0057.namprd05.prod.outlook.com (2603:10b6:a03:74::34) To LV2PR12MB5968.namprd12.prod.outlook.com (2603:10b6:408:14f::7) Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV2PR12MB5968:EE_|SA1PR12MB7039:EE_ X-MS-Office365-Filtering-Correlation-Id: b87fe601-0425-4084-c60f-08dd78638836 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|1800799024|366016; X-Microsoft-Antispam-Message-Info: =?utf-8?B?Zy9vL1ordk52emF2bVZiSGIwSDVQM1gxaXR5OVoyRDJId09FQ1pJN2gyNzNT?= =?utf-8?B?ZHZsUTZNVnhNTGFLKzNDWUJDQXBESHZMWXpiQ216MVpJRjZ6c1M4RkhicUI1?= =?utf-8?B?aXVjNG4zeDZ5c2xadC9LaGxkQkhxRlJnQVhFR1E4WlNXWXpnNmRsWlNSUjF6?= =?utf-8?B?SGFIY2pnV2dlNzRpblZZcXY5YlZSMFVabUFENHJMM3JENkd2c05sOXRIcHBY?= =?utf-8?B?VkxkaGRVUDdFaGFKcVNGRlJIOGJ4cmRwd0F6bEJOOVo1OHdYaXhOcG1aL0p3?= =?utf-8?B?YkpMWE5hRWpMRnFKM2lteDVpQ2lSK01ialNVRDBtNmJ3dEpMTzdaRC9YSnBN?= =?utf-8?B?enpRTXVoWUxJaTh2cllMZkxRdzZvUjhFdnlYYm1yT1RxZGtYNjd6QVdkK045?= =?utf-8?B?bzFvZE5QbitCWi84R3NuQVNEdXZlSDBpOEVFV1ozbU8ydVJKcE1vTXBqbTJO?= =?utf-8?B?ZWw1ODA2YXZHYVJwemRtaCtOWHhHV0VsRU12dEdYcHdadENSQUtsS0RjQjB4?= =?utf-8?B?VG4vczFiQkVlMTFvMGM2WUxReVdnVDcrOWpXZWVsSDlBWGRDQ1Z6VU4zSVZs?= =?utf-8?B?MDRpMER3TDIxLzZWTkZJZjVTM28rVDViUFBwK2lSaFlMSHBGZW9nRmo5bVd0?= =?utf-8?B?bnVJRCtuVjg1TFA4aE1lSXBlL0lmME5sQnJPU2ljL3lsSU5rM0ZRaWMxNDZy?= =?utf-8?B?QmNBcysyR0dCcyszd1U0MUdXVUt6KzNvMkdWQ2RkSDBhNlp5SnlUeTllN1ph?= =?utf-8?B?MkVPUUV5TEttTEtxdGc3OGxYOFU0UHRnQXRYREVCZndCUUxWSVNCdTRmYVh6?= =?utf-8?B?MDBQQ0ZrMEQ1ZDNlN3l6cURnL0U0Q3pyanVtOWl2L09QTVF1OEEzYm04cHB3?= =?utf-8?B?aWM2dThXVy9RckR4MHByVXcyV0pyVVN1Y3N3R3RSWU9qNWRvVVY5WGJzZ2tN?= =?utf-8?B?VDBYUGhnWGZrZ0pBZnBIVnV4ek9WK0tBYmVtWmVJRk5zVm41QVRYN29BRjUw?= =?utf-8?B?YXdocW5NRzU5S044UVpHNGlIN0FqWFlhd3ZIMEkxV3REbVFpaHFtRm5EU09O?= =?utf-8?B?emlOS1dpOGZGYlZPdzJrdEVIZjhxK1hPd0NNZmN5U1ZBbG5IcGNOWVN3L2JT?= =?utf-8?B?RG5vbC9OQktCRnFteER6c1BpZ0JKWTNzS2Y3eDB1b21PZWdvOG9zUHh4SjRP?= =?utf-8?B?aEVZNEV5cmVaRDhDS2o4ZmRmV2poOXpYNTExdkNGelB4eHF6eUUrazU5eGhv?= =?utf-8?B?SDl5QjlrSVlPRHlOTnJGNjhITXByR3kwc1RNN05Hb0UrVXlWdXlpRk4yOVdK?= =?utf-8?B?MDRrTEhueUprb1Q4ejZiSEx2cEdmdFN5TTRaNzhmVHdybExUcCswTWhvRmEy?= =?utf-8?B?S0lyZnFrOFZTWlBXOVZrcU1wQ2RxcDBOK3VBczZadTlyM1ZmY0hHdWttbE9M?= =?utf-8?B?dzVOTWFkRWhQTUVNcm9LQzhJbU1GZDlFRGZTYnhmeG9KRFo1dzJuZk1uVFVZ?= =?utf-8?B?SjJ2NndvbUFnd0YyRUFwYkhaMGVNQ2U0SVdWcUpsTzRZTnY5d1pCRWlNSU1V?= =?utf-8?B?Ly9mSUVEaFV6UG4wV2dvaFFENG1Jd1E4bEZJUXJJSFlNckZWK2UrMHVPUGxn?= =?utf-8?B?NmkvcE81Tkg3QjJPSnV2Rzg5UnVWUzVkRStvQzc4VTErV1VXT2I4WkVGbTdR?= =?utf-8?B?ZTByTVpQN091aDdVbnZKL1N5aG5TTVRWbkQ2UHB3SWhjSFVSc1VaaWNuUjJJ?= =?utf-8?B?L3VZQlRtUlJJRWxUeERpVTJxdTN5dVczb2lJbnVjcnlKTEtOeUVaQk4zQWVp?= =?utf-8?B?eE16MWJZUHpLSHlHTWdDZFFOMUhqeTJzRUZVWklFOUZRNVFrd2sxNndMcXNi?= =?utf-8?Q?T86taPM173q2x?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:LV2PR12MB5968.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(376014)(1800799024)(366016);DIR:OUT;SFP:1101; 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But we also do a second pass on I/O completion > before the buffers are unpinned. Which I think now that we pin > the folios is superfluous. > Oh actually I think I was wrong in my earlier reply about clearing the dirty bit. Because in Jan Kara's original bug report, what happened was that periodic writeback came in while the pages were pinned, and cleared the dirty bit--and also deleted the page buffers (file system specific behavior) that are required for writeback. So then later when the pages are unpinned and marked dirty, that causes the next writeback to fail in an unexpected way (it used to cause ext4 BUG checks, in fact). So the problem here is that these pinned pages can get cleaned while they are pinned, and then dirtied again by DMA (invisible to the filesystem). thanks, -- John Hubbard