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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?WpYvQn/pgJOphORmmHUrOlQaYcITOVGmMpJb+uAksmqg6pFSQX539LOgcgV+?= =?us-ascii?Q?8cBIXiWXAOURUZGOkzv2c5yzaYvh51+X66j2DgghCvoCz+e0I6XGpDUC7fQ1?= =?us-ascii?Q?Wj6pvYwfjJo8AMLNAYqs6qAQcfPCf1E2m5fKPuNygIgIIrCSwmuVgzdvJ8m8?= =?us-ascii?Q?7esLiXGsyY7nHbwZh7ftglnvVNgQAxXR4E5FYP4dD3j9c9sGZ0oHAREflXot?= =?us-ascii?Q?7U82cgeGlk7n4IQBxxk26569QCaP5fTGhaw3928FO8ECI2RByQdParoLhr2Y?= =?us-ascii?Q?FaGTwILycYCtZMg3fuLyElO6MzJXfwKa4sv6qWwRLbLod3pkK/NkQfHhO3Hd?= =?us-ascii?Q?Jd6KmBl5Dwn5wgWaEN3VHHPH4c9rVNAbtkLB4v9xDRL7kKZBxzO6TmT0IjGK?= =?us-ascii?Q?JBA1nRViz81vKnFfr85Ed3vLYPHJYPICZwNnUDXSOOnZ5GRPOusEV3vvxVV1?= =?us-ascii?Q?6czQlYEBIVZjvrM8mKtDkVDYq1O1PWQKcCNYo7ZYH1VJLXLjFYx1D9KhY8by?= =?us-ascii?Q?xlQbRQlnR7zFD/0ESQxiEa6onWZzgXhOc+5IfVzZ4ed70yKrU/VcgyZDC3gO?= =?us-ascii?Q?nkR3/T8k6Llm1Lx7ntde8OqKMCwc+Z+YfR8LXqdDAXtlhufgAp8hlrpzlhbB?= =?us-ascii?Q?eIhOTYUWxSROcnFPbB8hBNVU31E7cAIsu/rrEVjdgYXEZGwz89zQdcs32+Rh?= =?us-ascii?Q?1Jg75hde1XkktlbhXmfSuW+P9YpF86SxhJTORpQ9ophWKrH0lHRJ/qeWQ2AX?= =?us-ascii?Q?h33k4yuv0+Uw8a2NcWKbz0aSwddI752bUsm5yBLAvoCX5ysk8xB4VF7RcepM?= =?us-ascii?Q?NuSse6ueuoi84tT9vJSV6F/A73j98jbrsYFz5F72UD2p1RfF8avi7YXXJbZP?= =?us-ascii?Q?zHWHH5ag0UAmclfK+7+IBrfrkLsfcU+z7I9HqsReWqX1Ds9VOxHGAOpQxMX+?= =?us-ascii?Q?aidoZhbxHFuTfSghAgDtXo2KRJ1yet+T3mvCOUq41NGS2odYBNWXunEUo2ne?= =?us-ascii?Q?sSRtQLzzQYr2q6hUp5l4mjy7PeQIasmpk8ndB55YF7QEql/6ZLdslVaHDBKR?= =?us-ascii?Q?vq+ttXB25iOV5tf18/kHHkjDlB1bSeKeL6zRar4N04geJjbKZJqjeIV+x9WO?= =?us-ascii?Q?BNpq++EfSKrMJuSZVw5oXxADKsw67xj20JkzGxqiwT7wTS4UQJEpRATSpUMX?= =?us-ascii?Q?jGH+ZTldaMNPf2JzzF45FVvt1opuCOwco9PFkRPt47MxQHVdqP01DeeAU2hp?= =?us-ascii?Q?CKKgI2cgbuLWgvMDh71LUR8QKv5jV+4yr1xUT/djwhmkzVwBXyu+xLnWotno?= =?us-ascii?Q?tp6Y+KuU7r0XCTvSr+rn4TcGmwb9ZtIyocM9U4sSfoxPknxHXf168VS7Y6G9?= =?us-ascii?Q?sWyv42NK7YsWlqKZiXhZSgI4Hro1N2SO0dfTHIJUxx6VoZoagnlMZ8C/boxk?= =?us-ascii?Q?ReGb9lPrp3fLv9U2v3tTfbNVJKVtxQcVzVU2CF6DbpHdlXWrW86lbDeXNtHi?= =?us-ascii?Q?m95iaotw6zlNv4fkHruEbd/esBshdhMNp2PHPLHBfPsEKIyd45DFgy3Mbn/z?= =?us-ascii?Q?I3RVsGqPz6pe5nYVTcs=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 0ae223c3-077b-49b2-a0d2-08dbd40cef91 X-MS-Exchange-CrossTenant-AuthSource: DS7PR12MB5744.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Oct 2023 21:13:42.8185 (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: Tz0HYUE0UBQvwFNQ0YBlgDCTMSyhlsQJpx7zlNdOXHGzWc7wlN0F7o3tT9UZn/Sj X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PR12MB8253 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=_MailMate_D86EACED-A378-4159-9984-CA9DCCBBBC59_= Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On 23 Oct 2023, at 17:10, Hugh Dickins wrote: > On Mon, 23 Oct 2023, Zi Yan wrote: >> On 19 Oct 2023, at 16:39, Hugh Dickins wrote: >>> @@ -1170,6 +1170,15 @@ static struct folio *new_folio(struct folio *s= rc, unsigned long start) >>> break; >>> } >>> >>> + /* >>> + * __get_vma_policy() now expects a genuine non-NULL vma. Return NU= LL >>> + * when the page can no longer be located in a vma: that is not ide= al >>> + * (migrate_pages() will give up early, presuming ENOMEM), but good= >>> + * enough to avoid a crash by syzkaller or concurrent holepunch. >>> + */ >>> + if (!vma) >>> + return NULL; >>> + >> >> How often would this happen? I just want to point out that ENOMEM can = cause >> src THPs or large folios to be split by migrate_pages(). > > The only case I know of it happening was when a file was mapped, then t= hat > file truncated (cutting out the source page) before migrate_pages(&page= list) > reached it - rather a syzbotty thing to do, not of great reallife conce= rn. > > I won't assert that's the only way: I've a ghost of a memory of another= way, > that I can't quite resurface, from a long-ago version of queue_pages_ra= nge(). > > But in the end just didn't care enough about it, because this is really= just > to save a bisection point from crashing - the possibility goes away in = the > 11/12 commit which follows this one, which takes VMA out of it altogeth= er. Got it. Thanks for the explanation. I should have finished the whole seri= es. -- Best Regards, Yan, Zi --=_MailMate_D86EACED-A378-4159-9984-CA9DCCBBBC59_= Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQJDBAEBCgAtFiEE6rR4j8RuQ2XmaZol4n+egRQHKFQFAmU24gQPHHppeUBudmlk aWEuY29tAAoJEOJ/noEUByhUqoAQAJFk8tmZNpx6vUdhzE3SbIIxSlp9fk6bRe76 /zHj7yQFMmtQjlOIbO12GfySnFFPrwSqJruMwda0NVbXWMl/7QP7Ehe2PlADhjHz kt2bLm3/dRJxCcRXruFouIMJEtl5VV4mhdzJ8+mwUBSycdCgfUA3LIpvwQYfuLoN CR1EjsXNsQqjPIDVdRsZ4y7ofg9SToLsfuTxbh//h9fcN/61MZ+FzXtUqvB00mqp j6TUPx7FGf1KWCnO3WBfCa4ljbV0rCOK2+x+OH/TUMoUkOoAXYKWCB+Ph3F/4zOp YQg9g/yhLdlYEKRg91DaRcvxTMC/CMg5F9oY8x6BgD4KEJfPuTOEBsjFTWvRE0n1 UDulZOjIpzJaHPYLNuRv81RS2H3MJA2pJ+4xZhTT2uWMmfGdehcEJ3dN3rR68AWn 9X90z6FEZQR9pfEOIzKlHorDaQd3rWzCqxIJmI39GBI2SVyf6al6tZeNoT2WxNA/ PwsFff1dKDDTGAYN3RuYQYvOBqPbzVX49TizOM9c3StPmNIGirtxCRlCQNoDZCeJ w62Ov8zqs+EKBEJmdLX1lHyxFE5Lfx+0H4/QUH1lkTuNq1Pafj1sd1mXAYGnKum7 l0weoKJaDznjIHY7bZeW7fEpK0+8HrgboIdz4DgmqNCWXJlJ5VyAxlqYA7l+uAIA NYzV3KdT =WZrP -----END PGP SIGNATURE----- --=_MailMate_D86EACED-A378-4159-9984-CA9DCCBBBC59_=--