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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jens Axboe , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Muchun Song , Oscar Salvador , Brendan Jackman , Johannes Weiner , linux-mm@kvack.org, linux-kernel@vger.kernel.org, io-uring@vger.kernel.org Subject: Re: [RFC PATCH 0/5] Separate compound page from folio Message-ID: <20260204184911.GI3931454@nvidia.com> References: <20260130034818.472804-1-ziy@nvidia.com> <70e06ac9-5cbb-4616-b20c-33f5bc1601e6@nvidia.com> <2EF8F5BB-7CEB-431C-B9CB-00B1E3E44E1E@nvidia.com> <33B161E0-5468-4A31-A5BC-B4F1FCE72CEC@nvidia.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <33B161E0-5468-4A31-A5BC-B4F1FCE72CEC@nvidia.com> X-ClientProxiedBy: BLAPR03CA0013.namprd03.prod.outlook.com (2603:10b6:208:32b::18) To LV8PR12MB9620.namprd12.prod.outlook.com (2603:10b6:408:2a1::19) Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV8PR12MB9620:EE_|SJ2PR12MB8739:EE_ X-MS-Office365-Filtering-Correlation-Id: c2695b7f-bfe1-45b3-5cd7-08de641e16e2 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|7416014|376014|366016; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?nuA8b5iv4NVfJr0fx7i/wqLarH8iE+Pj/q+GvmoGGlYuPsJCx/MYK3iBiTsK?= =?us-ascii?Q?9peeMW21fNsu+9rIIT5prHhPtIU3iSCi8oDDrvmNmmY4iTPa9Viap38qDN9G?= =?us-ascii?Q?XKo9mWiST29q3OxDLFFZOcIxC3G9CSohWVUuqk1VjaIlwK+XC5zH+AVOdrM8?= =?us-ascii?Q?WZCs8ND0fh/wzk0lgKQU5SUXxHwxFDRu2hpEmBLZ3gbtjlX1f8/lcFAgYWAm?= =?us-ascii?Q?sBX6g92o/LYSlMqIlcy6e25Yp4FsGnvl+YApFg7X5w5FVoIiGpx4DVzGUDpB?= =?us-ascii?Q?a8oOnSqPyD6EcMOa7lTlRR7nMtTAsVHqkFaSydPd+ee50j8n8G7R/Okfmf/q?= =?us-ascii?Q?FEVGgKL4qyOhy/lPdsfZAtuXG4P/shmNTXZbVvgWqFve5Ruyzv3/Z/UuVWJZ?= =?us-ascii?Q?lVBc8zUBtm2p8B9WJKORI/hJdFpHMDdV7IuC5N4SfR3bsyLFawf49OtQo9Sb?= =?us-ascii?Q?glFNmFvFEHb7MjqBXKmfT9Gk+f6uaQWPAJ/fRM+Sj1mxHqC+VS0zGKBC/WKJ?= =?us-ascii?Q?iBD5x74H1l2pAnapkWMEbV78Ksp39VAwoVcBIswbbZgEqVbNFt68FzERSoRv?= =?us-ascii?Q?xg2W3H7GBDtdfAeTrZ+9dhYsmFLaUA3uX5eluKwg2UefH62ruSv77c8bFyoy?= =?us-ascii?Q?97mE/YT0QaaGCq5jsjfnnsSnFJpFKEWSLcx3qLUkOmm+HNdQSkjr8IVZxox2?= =?us-ascii?Q?WbXy2oEoOzrG3C9qo0HEoR0aK/tf92zEMIkuQBfpRvmygJz3J2fqUi8/+Em0?= =?us-ascii?Q?T1ye6lsgWaxniZEUcaD0EaiK09qZo7Lott9KX+MaXSWP7/E/ViHafMeG5CY5?= =?us-ascii?Q?dBqYf7aZUhH0W9hmn3pSkyKyGPQWtkKgARCO7wAbzt8CARIBe4JRb0zI2wic?= =?us-ascii?Q?gxzNXdkAQZQ1hioRYks29ph4iDACA0+BZdLgbCYsx9REpospsAAOeHbJ6xRJ?= =?us-ascii?Q?39+rL1LCRqFG5N8Vmt1rd6qapnBn/6/ChFn8Lxc371oPjzi5nN9vNU1cg/cK?= =?us-ascii?Q?YLxUx/WINfngF7V784kgEo1BIRPaNBQUsh7MPkDgpro+Nexy7gs8I8DxmWx6?= =?us-ascii?Q?m5eE2cdtk89QLElnq4tHu6qGdv1zP984WxrFYuADmoLM+uo/95j5vHq1pRHD?= =?us-ascii?Q?p42K7rG6M4Ag5EAtKzCYJ7lG/ypoDFAik1V6CyWseWJjtJWK/NGsjPvUOR4r?= =?us-ascii?Q?Ybyo6p4chAUi2iil4ejuscR8Bmv5DuXMRlcvf0JwzHvajzaLfSt+INLk3w+b?= =?us-ascii?Q?T7WWlbpPAsafTajDJ8aq7YO5gWiCNInCO79AwSvR9b2H4YIE+WrFMxjYkyt6?= =?us-ascii?Q?Ts5nw3Qbxcn0G9QrTBWx7JjQTd0LYZAJ46rsOcl79KPUlBW8xbZBqxSo9dFy?= =?us-ascii?Q?hiPoybTlLKn2SVPlRFtt7Fm7juctZIQySOcBTX8A3p+GGAH0gZhJiTiDSdk7?= =?us-ascii?Q?Ylz9jVyugKBAEZqWC1DDypxPlup/byXYS2huqNLIoY9B69pgFyAiM1sJ6QBu?= =?us-ascii?Q?isVYq+iS2S0MGT6K5R6Se9yHZlqbcp7VixpVnY6/BSNOJSuv46ZAsH4c3bTY?= =?us-ascii?Q?CuRW3aEiIqDqQpTcJgR8GFIEMQgXORVmcTw6bNTkGd1zNYl7/tSSq9q22Fq2?= =?us-ascii?Q?W6YOElrqFsq9FdOHAS6o0QgU9vNWMyS8VffPwshBsFBau1oyX4z0XZlC8U78?= =?us-ascii?Q?jTXPccyru813l3VxIBbsPwBBaQJfTp82NE/VLnC+qAu0azB9UiLHPkDuNMhA?= =?us-ascii?Q?VBGUTiL3fw=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: c2695b7f-bfe1-45b3-5cd7-08de641e16e2 X-MS-Exchange-CrossTenant-AuthSource: LV8PR12MB9620.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Feb 2026 18:49:13.1389 (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: wzjvfb9t2P2OU5ZmNYotyeYHY9XYkXpQ7xGqOEcM31cBQKbaieU/HR+7ookcwrkj X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ2PR12MB8739 On Wed, Feb 04, 2026 at 01:29:45PM -0500, Zi Yan wrote: > > For in-tree users, I am converting them all in this series. > > Considering a recent report[1], where drivers/scsi/sg.c allocates compound > pages with __GFP_COMP and maps them into userspace via sg_vma_fault(), > I guess almost all __GFP_COMP users are really using folios instead of > compound pages. This would be my guess, and it seems like a good cleanup to make them actually create fully proper folios if they are being mmaped. I suspect the only places not using "folios" are frozen page users (or places yet to be converted to frozen pages) Which is back to my previous remarks that having a good definition for what struct page memory is allowed to be used by a frozen page user would be helpful. If the mm can retain some of the tail page memory for itself you don't need to make several of the changes here. Jason