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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: [RFC PATCH 02/11] mm/khugepaged: remove READ_ONLY_THP_FOR_FS code in collapse_file() Date: Mon, 23 Mar 2026 15:47:02 -0400 X-Mailer: MailMate (2.0r6290) Message-ID: In-Reply-To: <7382046f-7c58-4a3e-ab34-b2704355b7d5@kernel.org> References: <20260323190644.1714379-1-ziy@nvidia.com> <20260323190644.1714379-3-ziy@nvidia.com> <7382046f-7c58-4a3e-ab34-b2704355b7d5@kernel.org> Content-Type: text/plain Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: BL1P221CA0035.NAMP221.PROD.OUTLOOK.COM (2603:10b6:208:5b5::8) 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_|CH3PR12MB9028:EE_ X-MS-Office365-Filtering-Correlation-Id: d0a15440-f285-49a5-e766-08de8914f661 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|366016|1800799024|56012099003|22082099003|18002099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?KxiwWQTf1fq7u14JpC5LmrnNrITAwDxbm22/pYLhEkzlLJAK1mMY/rmhe+gA?= =?us-ascii?Q?Rz9jhM3lCjuO/PivlbOB6DFQuAXvAWXzAhWdwz4hz5Lt/mYEQZeX/mCtSnu5?= =?us-ascii?Q?OFgfhKMgTBWprK7B3kGS0FmFTQPmGrBVWGmyt5s0iFwKcuj8sHkQZb3uEHAX?= =?us-ascii?Q?perC76ZPmq+uMD1XLeT5mveAhzQ/2ZOdYVZnqPyJFaMFGruqk40jg9QO+eRJ?= =?us-ascii?Q?tTDvoTHQMYfpzh5Xubc5XqqXJMNsAiow4yMG+OJHDjZ/JE8X5Y2wY9JI83Gk?= =?us-ascii?Q?SYm7+nr5Xg4Qav8SwtHf87JukAIhd22aO1JWQrqY1ju4jrp0EQxzcPHNnZn9?= =?us-ascii?Q?90T3Inu+wHLh3tjo147C+BPkz5Uji17LYok8GvqCfu3P1COgugI4+NEgXKWq?= =?us-ascii?Q?11Osu1D6uNSl7r5xnhcwN64vT5L6QpisQi4CynsUZaiM5jefR5EaYXZPZxhg?= =?us-ascii?Q?gNrl8Ykko0tGOtEZGUsL+0GhdxKGP+UeRRns1nHc4XZ0lNGSAJ15aMLlOpiZ?= =?us-ascii?Q?14XClt5h2PbE/qN0sKXDaMmbrDFMXuxd73JrAleea6F0suW040x5hWakt5Hd?= =?us-ascii?Q?ICTCR8tOInm+4L2MVnOrpHai/dMFbqEHxjbjXZBb4U1eLKRgXcGsWCuXq4z2?= =?us-ascii?Q?edq+BvBlknB/bMREn5ISmY2GPt6DWIyd5lbPEQrlRv00fdQwh0iTcykmuKjy?= =?us-ascii?Q?CPD2auZB/YoRO/MV6KVpZFjGliERNUh7gdlg2fNi498ymLz/5Hzd0FYPpRua?= =?us-ascii?Q?Mvbq2TTP/HyHBWuaLg/sm0X0XITFY7WcJUUw1xVfTrnyAztOYmrZEKixsM4k?= =?us-ascii?Q?HhBfwSrM3kSn9+wodU+JcmNR9qB5rxQOk1mRYPWTzoTLxI+mBGgu9dCVT4K2?= =?us-ascii?Q?cNt2GqST6Kj/V6PgP1ir2PL6lwWmMkp1iIMZue4ZvPAJ0eSGFlGJ/UWa2Iea?= =?us-ascii?Q?jfKlncFJvwxvzePkjIn+tAGPJM2gl/NaDpvIPT5mxxpUpi5NQrfmYZSPIf8g?= =?us-ascii?Q?IeeWpsiYuaIaZNc/B8EkYz09NNcz3ngUHRer7yAq2uD1h7/lytd1qe9N3dMe?= =?us-ascii?Q?9pz2MSZMzcvCCt0NGhD7B/i8cS1kHf0B+NT2HnWzsc6lus8/rvQ3yrSZlij+?= =?us-ascii?Q?A0vhL0CylIznhYgxwUy4QxDyU8dQ7Lo4baqvqm9gCMz7QZBu2ZSlqxLRkXfS?= =?us-ascii?Q?3MMa0Dr9zlcmf5hZMOVKhzFIN6RBZ0Oh1lS3x6KTY3VR/oHfT6NEkgL29JZa?= =?us-ascii?Q?b5n2SfdTbsN5siJd3yAtqOWc2JBgCSPNol9D0mVsxpQR5oDEBbIAIzK6yAQh?= =?us-ascii?Q?kMa9Recj9Od7qXhuQaTdf+6tfK1s4FRubSpiiu1pIPXTsPcfzrXdLyAddkLk?= =?us-ascii?Q?fN3w76KXZU3jpqQdJ5dRLNV6AYokT0psesxGFtq00bdaGoQznP28LpuufVCy?= =?us-ascii?Q?otMBOa/I3oYNTaSZu/nnapv/3J3JOu8o08tIInbucJmHjhgl7qZtRN9ip0LK?= =?us-ascii?Q?rFRdyymgse6WqHz5Y5j4sB2ls4jBGA5St0PbVVFT+KkXRXAerBY0yYJRSX57?= =?us-ascii?Q?MMF7Ed06igIq6BvrxjibRCQ5bPnJGqGIDCQTnRFyDlmvnYXQqkb5smp/vWql?= =?us-ascii?Q?nXjzrbJP12JQpVX3qnlC2iWmu27j8OajOyv38cj2QHPk5To/SKeqk56JM1wd?= =?us-ascii?Q?S3r9uOW4XYKfjdy0NpIq7vm+O+69PNYeRr5T2uldLwUOYmiEHWpJbJu+cXJE?= =?us-ascii?Q?UjPtl0VFQw=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: d0a15440-f285-49a5-e766-08de8914f661 X-MS-Exchange-CrossTenant-AuthSource: DS7PR12MB9473.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Mar 2026 19:47:06.1054 (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: 8vBpcZZBQymR2+SdNmulTzw1PVRErvtY4E5unx4zMs92XlRhGebOOMhrrVF+FEEf X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR12MB9028 On 23 Mar 2026, at 15:41, David Hildenbrand (Arm) wrote: > On 3/23/26 20:06, Zi Yan wrote: >> READ_ONLY_THP_FOR_FS is no longer present, remove corresponding code. >> >> Signed-off-by: Zi Yan >> --- >> mm/khugepaged.c | 159 +++++++++++------------------------------------= - >> 1 file changed, 34 insertions(+), 125 deletions(-) >> >> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >> index b2ac28ddd480..39f0b8959535 100644 >> --- a/mm/khugepaged.c >> +++ b/mm/khugepaged.c >> @@ -1899,7 +1899,7 @@ static enum scan_result collapse_file(struct mm_= struct *mm, unsigned long addr, >> int nr_none =3D 0; >> bool is_shmem =3D shmem_file(file); >> >> - VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem); >> + VM_WARN_ON_ONCE(!is_shmem); > > Oh, but if that means that khugepaged cannot collapse large folios in > FSes anymore, then this is the wrong approach I suppose? > > I would have assumed that we would now collapse for any files that > support large folios (in PMD size), not stopping to collapse entirely. My understanding is that collapse_file() is only used for READ_ONLY_THP_FOR_FS. If FSes with large folio support also use it, I can replace IS_ENABLE with mapping_large_folio_support(). Best Regards, Yan, Zi