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Subject: [BUG/RFC] write-open file THP cache purge can discard dirty page cache Cc: "Alexander Viro" , "Christian Brauner" , "Jan Kara" , "Matthew Wilcox" , "Andrew Morton" , "Song Liu" , , , , "Eric Hagberg" , "David Hildenbrand" , "Lorenzo Stoakes" To: "Pedro Falcato" , "Gregg Leventhal" From: "Zi Yan" X-Mailer: aerc 0.21.0 References: In-Reply-To: X-ClientProxiedBy: CH0PR03CA0417.namprd03.prod.outlook.com (2603:10b6:610:11b::6) To IA0PR12MB8374.namprd12.prod.outlook.com (2603:10b6:208:40e::7) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: IA0PR12MB8374:EE_|DM4PR12MB6352:EE_ X-MS-Office365-Filtering-Correlation-Id: 54a2a9b4-db0d-479a-09e6-08ded6f9bb2e X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|366016|7416014|1800799024|23010399003|22082099003|18002099003|5023799004|56012099006|4143699003|11063799006; X-Microsoft-Antispam-Message-Info: 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Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 54a2a9b4-db0d-479a-09e6-08ded6f9bb2e X-MS-Exchange-CrossTenant-AuthSource: IA0PR12MB8374.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Jun 2026 22:48:41.0217 (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: 2ee6PzQmrjjqvmU5vqYemQ9Ra4F86LvBrlwQBWxlQz1KihQpkMxh7a+G97NrV8nx X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB6352 X-Stat-Signature: 6so3ifjdcfma5ysddztmrnbh55yrcin4 X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: A554E40007 X-HE-Tag: 1782859727-872882 X-HE-Meta: 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mCAzLdoPXed58f4Fk6AIjexZUvoeIJnmqOhO2Qccumi1Ux2HMt1QGHLSOfAWTHb3BKiJhvpKOlDIie8CofuxRwa3a/CCHukpPdub2sJkKQCsDgCBaE0WCVmxcIt0ttQG6YQ0QFk74unr+NOg2zrFu9j3bWh3IGoJGGJX6ZDLFPHYvm+nczV8Svbg16uF0CdhFx2vtc/t1kO1rFeNArE71RyiUL0NRhQWhCF/m0qu1aqVPQv6M6GnUkTfR8Bdm/BTBViybsO90f/7FNL+lSinaXWC//rZglYsE+kHX0ndHlO0aQAHHd5hny/KzS7+LGS/R+A4KMqUx+EVlKGHyEqxgoLM0LSlWiNWSsitAJ7DA4h0nqoWeW1fDdJUQOL679Rm4RjxtzfX8CIojtzt2Cs/hnJ6F9g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue Jun 30, 2026 at 3:55 PM EDT, Pedro Falcato wrote: > On Tue, Jun 30, 2026 at 07:49:12PM +0100, Pedro Falcato wrote: > snip >>=20 >> Other idea: perhaps doing filemap_write_and_wait() after the nr_thps >> increment in collapse_file() will Just Work and result in a _much_ >> simpler fix. And it avoids any weird forward-progress issues as no one c= an >> write to folios at that point. >>=20 > > Gregg, if you could test this patch, it would be much appreciated. This p= atch > (hopefully) makes it so no dirty folio will ever coexist with a ro-THP, t= hus > hopefully sidestepping the entire issue in a simple way. Only compile-tes= ted > and not reviewed. I tested the patch on v6.12 kernel with the reproducer from Gregg and confirmed that the issue is fixed. Feel free to add Tested-by: Zi Yan --=20 Best Regards, Yan, Zi