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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Mike Rapoport , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/4] mm/page_alloc: remove set_page_private() in prep_compound_tail() Date: Mon, 29 Jun 2026 12:50:04 -0400 X-Mailer: MailMate (2.0r6290) Message-ID: In-Reply-To: <8b74962d-8dcd-42c9-bf97-7d6b83b52c84@kernel.org> References: <20260628-keep-subpage-private-zero-at-free-v1-0-f4ce3930d10f@nvidia.com> <20260628-keep-subpage-private-zero-at-free-v1-4-f4ce3930d10f@nvidia.com> <8b74962d-8dcd-42c9-bf97-7d6b83b52c84@kernel.org> Content-Type: text/plain X-ClientProxiedBy: MN2PR07CA0020.namprd07.prod.outlook.com (2603:10b6:208:1a0::30) To IA0PR12MB8374.namprd12.prod.outlook.com (2603:10b6:208:40e::7) 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: IA0PR12MB8374:EE_|CYXPR12MB9442:EE_ X-MS-Office365-Filtering-Correlation-Id: c18810d1-30bf-4608-0b07-08ded5fe78c6 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|7416014|376014|1800799024|366016|4143699003|56012099006|6133799003|11063799006|22082099003|18002099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?9MMXR+yJr8Cm/PM8Uw5BgEtLSM47CZC+tk+oY9Wb69KMF3laQsmDgoqC3m9Q?= =?us-ascii?Q?+shZmuB10tDfmVeq1pTOpkP/p9kBXF5avGnudS3LDfR416XhWxnoaQNnaXhr?= =?us-ascii?Q?2VX/4PGElAh3j/ElOcEUXHmqTfXKBIecqZU/0nReiKHvWtwlkqM4gHIHY5eJ?= =?us-ascii?Q?vwsYFlxHq8lMHkVTNIwROf2R+K13CdmWuoVWyS4G9v71jyXv5Gq8fyTXT8PJ?= =?us-ascii?Q?5002yBSi4Jbca3GMOLP/rBk3bDdE1/2fM0YkRkKUqnulB8OSdq8wIqk39rDi?= =?us-ascii?Q?/J9cciiiVhyn8+xGKDBMiHpCButLSztYRRl7Eb0qxKqCidumbr/qXLl2lMwv?= =?us-ascii?Q?jlWSjaLx8+0Igc43GC2ZmMvHDj9kSGZEDT/qOkU7xJTZp6TyuHkb22EmJzek?= =?us-ascii?Q?HfeOJmj+u7jCigfXJCV2CSd6CkiNPnTerUXmG10MX429Vc/h3DOzIJeYr3ZU?= =?us-ascii?Q?1waiuTYnOGVcD75iXNo7FPXBy8IOubhqeVJHdz7N8ozpzihrJ2feQf/4yTFg?= =?us-ascii?Q?bSm8oi+Japh1W8AjHlrZyTSEsOp+e0CtXaPAMOYks4nPHQRedraTK/u+IZCh?= =?us-ascii?Q?8jH2w4FUhVRcL7+i1HkKfLW+iqSqF7GjQRdhek8ChfpP9fQ0SxCnz8K4IMy7?= =?us-ascii?Q?9XozkGAqaklEcqOKQpYxKjeGsETIsemcd4VfOhrOSwHUE4zNF0/qMmPm8gIs?= =?us-ascii?Q?N4aGxIIlmXQq5sQ/DqOmQy/ii91kbQ7BrkvkqHjbpvC16E4t/PJObrEIlCr4?= =?us-ascii?Q?PJ2ndefjQG9C14L5jEcc+fdaqfQ/nUmBvoEPzDp4qVJ8kzkxpjWIuVOodvZG?= =?us-ascii?Q?jGsLXCotdnDt+UH7Ure9LYMfr6gpztU00iCMj2X74MHQW4FlqLCkVTctKUW+?= =?us-ascii?Q?/gLX0zTvkdBgv1O/LHhet1Rb++/QnK9SYPhkf6DQ+wz8ieAjmtqfI+xmhlLD?= =?us-ascii?Q?LbzEDnwqbxhQUV/K7M6fIPJf03pjGRSgkcxc0Sci4v2rW+GXYoiq+nuCI2xd?= =?us-ascii?Q?kR7BM5/xArjugmwY0cF6xlo8vZdfTJ4Jx1IpaERiqxlKZcKBO039mx81mQAP?= =?us-ascii?Q?iebMhv3p6wYvpzgbdqXIs2KU2t+bLubOvY06HrnWjXgziAQO0VkKEo92udNB?= =?us-ascii?Q?mY0IgIucdxfW+epdDDIBKpo8Cz0m4xdouFt0DQoTVo8hVG3cqgURMndOPPDI?= =?us-ascii?Q?/XpbsshpVeLAVvS3o9iTQPZWtCd6v4h/KSAlw1+HxpvdianQgpjcj/K/Kw23?= =?us-ascii?Q?Iom4U027msmu1DMOzHxQ9aGV242f3eHS4yV2HOe8QZ+gdn70+GB7wxt7luQk?= =?us-ascii?Q?KtaGhVtefTNdCKfuzo0bqPB7O3X0TVJ/nmwGBdXU/QmuOtPLpMuup+2YGCb8?= =?us-ascii?Q?Xr4oLaHfo1CrK8JC2lgAm/jtRZDKNdEXpE7jqDfOkfY+fHjoq8hBg+NmARbn?= =?us-ascii?Q?J793At6mAAWXy9bWxoCZT9aRRA9zlzVY6EghE7XN5DvR/uZkwmdaJmxCJOhL?= =?us-ascii?Q?OwOsiuCeGIOhxHc1g8LYFhnL6QI+SfENMQa1hJqE3mFAY+fvQeACFgllpfyG?= =?us-ascii?Q?OfAXf+ufEIOm8K51Pl6tSP149TmR98TJOlyFL/Y2Yd2NKhH83Rsl6mNinf63?= =?us-ascii?Q?1XB9+wyCeZos0WeTNQWpy1+KTqGWeIekA63gJcscoCxj8LizJZEqfM5q+FCj?= =?us-ascii?Q?5ZqSM7OJv+k/wmv8km3WfL5v4TXvLdTKcMZj7Gqr1RqJla8R?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: c18810d1-30bf-4608-0b07-08ded5fe78c6 X-MS-Exchange-CrossTenant-AuthSource: IA0PR12MB8374.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Jun 2026 16:50:05.9525 (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: L9QGdnkc7DCjzDhXn/55N1RiaJFFUSQDLRlpOpx0JspS1wYfAVECwjdlpTtKUsiu X-MS-Exchange-Transport-CrossTenantHeadersStamped: CYXPR12MB9442 On 29 Jun 2026, at 11:45, Vlastimil Babka (SUSE) wrote: > On 6/29/26 04:56, Zi Yan wrote: >> With the subpage->private == 0 check added in a prior commit, any allocated >> compound page should not have nonzero subpage->private. Remove the > > (not "subpage") Will change it to tail_page. > > I think the sentence would be more precise if it said that we now expect > (and optionally check) tail pages to have zero ->private when they are > freed, so we can rely on that still being true during subsequent reallocation. > > (and if the buddy allocator itself sets it to non-zero due to split/merge of > buddy pages, it will reset it to zero as well as appropriate, but maybe that > doesn't need spelling out) Will fix the commit message like you suggested above. > >> unnecessary subpage->private initialization code in compound page >> preparation. >> >> Signed-off-by: Zi Yan > > Acked-by: Vlastimil Babka (SUSE) Thanks. > >> --- >> mm/internal.h | 1 - >> 1 file changed, 1 deletion(-) >> >> diff --git a/mm/internal.h b/mm/internal.h >> index 181e79f1d6a2..c96421ce9350 100644 >> --- a/mm/internal.h >> +++ b/mm/internal.h >> @@ -895,7 +895,6 @@ static inline void prep_compound_tail(struct page *tail, >> { >> tail->mapping = TAIL_MAPPING; >> set_compound_head(tail, head, order); >> - set_page_private(tail, 0); >> } >> >> static inline void init_compound_tail(struct page *tail, >> Best Regards, Yan, Zi