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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v1 02/10] mm/khugepaged: remove READ_ONLY_THP_FOR_FS check Date: Fri, 27 Mar 2026 10:43:28 -0400 X-Mailer: MailMate (2.0r6290) Message-ID: <5AA0D400-B4D1-4223-9A7F-41BFEA176F35@nvidia.com> In-Reply-To: References: <20260327014255.2058916-1-ziy@nvidia.com> <20260327014255.2058916-3-ziy@nvidia.com> Content-Type: text/plain X-ClientProxiedBy: BL1PR13CA0350.namprd13.prod.outlook.com (2603:10b6:208:2c6::25) 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_|SA1PR12MB999109:EE_ X-MS-Office365-Filtering-Correlation-Id: 67d05382-098f-46a9-6615-08de8c0f37ae X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|7416014|366016|376014|18002099003|22082099003|56012099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?dbauky83FRQj2eqhvu3aRsrOUlGCP95pFfxbRZx7sRFmesDXOy4fy9xk+Owe?= =?us-ascii?Q?V+6lrz8y2ie++o064NdoToo/FNhPu+ftqTO5D0xjL4+mlrLS00s/+K3YFx65?= =?us-ascii?Q?vg54movRvdNDGrfIZl4I4p4AkCPKwKEe8xnAV9MDb+aPdLXfgl+hiNtiriji?= =?us-ascii?Q?twprn/wy4aw9CLGLN3tL7Mlpaff9GWmj6GCy6svbEmprT+yCcBoNsQZso1cJ?= =?us-ascii?Q?QX9ulNGxebWrIdNCp0Sd7JRIJ5rOTAh61huDDcheu/Ji4JGj7lkHkaUyVfPx?= =?us-ascii?Q?lC4p99BLr5LBMmu80Nhdvny14gjPAwlU4ow7vss7tdqwUdVVay3fmPFKhTdK?= =?us-ascii?Q?kp6jba/x9BQ8dK/61kOfsGTZQ3JB7mcl+VVCCe777FhEI4i693ZNHO0LrflH?= =?us-ascii?Q?MyrPeh9Qednks4jJ1r5Av+5pHRaN32860FIJrOBKD0LFf8IY9HAdRXstNhPr?= =?us-ascii?Q?s8H/Zr4UoNysL+fPEsIcdtX0EoCvc7Yj58s7JXtpZ2U2DU512DeVJBxN/v11?= =?us-ascii?Q?fyjDgKbnY2N0M0kyJRTje8y90N80CkfzgPtO3+OLnBWBDaFvkD3io3ZakVwv?= =?us-ascii?Q?679Qu3UDOqdOsrf9w6+2Z5EBi7sLC6fowm0QkFUvKZQEEzYVrgVl27gahMzf?= =?us-ascii?Q?QNMfQUt2ce8uePGelYkE5U+WnRfu6/8zH9CYopB+LSsGI/AHv2H26SVaB8rB?= =?us-ascii?Q?xrPSpiDEwUcRdHfVuEjQ+NqCW46+i8hU4WFlDi47jyQf+pw0/xoNU5Y8O/TN?= =?us-ascii?Q?MGC7HLH6nBDn4x7vV+MtD+4BdKanoyt1oedfiy+GntA/771o6o+Ql2uprikl?= =?us-ascii?Q?pATPThUln0Hlk1ykpaJfmiz8YI49RmZ0F/9B3Hx+egRaIEnPE+Bl69EOtCS/?= =?us-ascii?Q?oxO1s6pBiMKd8J/a2/XQR5JcWoah9+7rkiOTb6MVbwuDUq9094EmyQtjRRkj?= =?us-ascii?Q?+FpOIn8b8l7DlHyNzRr6toCpY6zEH/bIYSWRrFItZSKhcCNHtRQMms44+Bnh?= =?us-ascii?Q?TSMIVUFL6AN/PfgcyhjG19BWO6GUSs+ElFqsb94X6BUwaOEIWUE9oV1x8hR7?= =?us-ascii?Q?GNE6w8ez/xlifIoUwyLUO8Zv68c1T7Zx/Kzx26bnFu7Nz8rDfxFtwlJIVMkf?= =?us-ascii?Q?MO2lDx0OQYDE5mAiSWKakgsg1BY01jibk/QwMGKxIRhUIlSIUhWO6t65knfC?= =?us-ascii?Q?L2VMDCygdGZjRFdtwmB3xV5WrRG29zLeBqgmWTtHUDF7iBG6U+AUq1oVAgAX?= =?us-ascii?Q?USn8y6kcM+5R/5CmneSy1uZLQZ6wNyBWd4U8xDWHVY7IFYZFqyMd4IW2u34C?= =?us-ascii?Q?lkAITAR3nlz0RraCd6fuo6INQNkZ/vhgZhp7ksINb3PqhNYyycLVOo3hnRpO?= =?us-ascii?Q?v4RMe24QyzyFKCoW+A9fXwfe7Y7QpdPMMp+Zc5/9BgAZnXDDQ7Yeh4XUf+XD?= =?us-ascii?Q?1EpoBzhOEviZFT7UJB77i4n4Aa6uxRmE4m39L7JBZYXwOu7Uzap4tSFiDFwo?= =?us-ascii?Q?8joHEaRwraElRHY/qDggf0oGFGHh1dUGwrr8X9aUoUQ3qrltN9PHdzRWgHCd?= =?us-ascii?Q?3ei6FodXU8OF+/jImqUnJmNokjo3ydSbBtLU7zR2leYqAT5rdGqCvEyadIwf?= =?us-ascii?Q?qfr1YgoAd4JgpgagEjuUvwYZurYh70e1K0iTN0m5gX451zK87v4qF931g3ci?= =?us-ascii?Q?DOkvtJ2WJE2qEdGm+82lBnbb46LkhS0TPUE6rOtbjsqHcpUcCeLOhPNPRdHG?= =?us-ascii?Q?0dP5d8fBUA=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 67d05382-098f-46a9-6615-08de8c0f37ae X-MS-Exchange-CrossTenant-AuthSource: DS7PR12MB9473.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Mar 2026 14:43:32.1286 (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: BtmJnp/TaSb1guCAA51jQ+b7KiRpyudtiM0g70P9RpMB3eBv2GI2PwkRxOm1XFo5 X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR12MB999109 On 27 Mar 2026, at 9:37, David Hildenbrand (Arm) wrote: > On 3/27/26 02:42, Zi Yan wrote: >> collapse_file() requires FSes supporting large folio with at least >> PMD_ORDER, so replace the READ_ONLY_THP_FOR_FS check with that. shmem with >> huge option turned on also sets large folio order on mapping, so the check >> also applies to shmem. >> >> While at it, replace VM_BUG_ON with returning failure values. > > Why not VM_WARN_ON_ONCE() ? > > These are conditions that must be checked earlier, no? start & (HPAGE_PMD_NR - 1) yes. I can convert it to VM_WARN_ON_ONCE(). For mapping_max_folio_order(mapping) < PMD_ORDER, I probably should move it to collapse_scan_file() to prevent wasting scanning time if the file does not support large folio. Then, I can turn it into a VM_WARN_ON_ONCE(). Best Regards, Yan, Zi