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Howlett" , Vlastimil Babka , Harry Yoo , Jann Horn , linux-mm@kvack.org, syzbot+2d9c96466c978346b55f@syzkaller.appspotmail.com, Lance Yang , stable@vger.kernel.org Subject: Re: [PATCH 1/2] migrate: Correct lock ordering for hugetlb file folios Date: Fri, 09 Jan 2026 09:57:38 -0500 X-Mailer: MailMate (2.0r6290) Message-ID: In-Reply-To: <20260109041345.3863089-2-willy@infradead.org> References: <20260109041345.3863089-1-willy@infradead.org> <20260109041345.3863089-2-willy@infradead.org> Content-Type: text/plain X-ClientProxiedBy: BYAPR07CA0080.namprd07.prod.outlook.com (2603:10b6:a03:12b::21) To DS7PR12MB9473.namprd12.prod.outlook.com (2603:10b6:8:252::5) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS7PR12MB9473:EE_|DM4PR12MB7528:EE_ X-MS-Office365-Filtering-Correlation-Id: d77fedc8-03b9-4d4d-9e19-08de4f8f717f X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|7416014|376014|1800799024|7053199007; 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 hE88bFAg 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8 Jan 2026, at 23:13, Matthew Wilcox (Oracle) wrote: > Syzbot has found a deadlock (analyzed by Lance Yang): > > 1) Task (5749): Holds folio_lock, then tries to acquire i_mmap_rwsem(read lock). > 2) Task (5754): Holds i_mmap_rwsem(write lock), then tries to acquire > folio_lock. > > migrate_pages() > -> migrate_hugetlbs() > -> unmap_and_move_huge_page() <- Takes folio_lock! > -> remove_migration_ptes() > -> __rmap_walk_file() > -> i_mmap_lock_read() <- Waits for i_mmap_rwsem(read lock)! > > hugetlbfs_fallocate() > -> hugetlbfs_punch_hole() <- Takes i_mmap_rwsem(write lock)! > -> hugetlbfs_zero_partial_page() > -> filemap_lock_hugetlb_folio() > -> filemap_lock_folio() > -> __filemap_get_folio <- Waits for folio_lock! > > The migration path is the one taking locks in the wrong order according > to the documentation at the top of mm/rmap.c. So expand the scope of the > existing i_mmap_lock to cover the calls to remove_migration_ptes() too. > > This is (mostly) how it used to be after commit c0d0381ade79. That was > removed by 336bf30eb765 for both file & anon hugetlb pages when it should > only have been removed for anon hugetlb pages. > > Fixes: 336bf30eb765 (hugetlbfs: fix anon huge page migration race) > Reported-by: syzbot+2d9c96466c978346b55f@syzkaller.appspotmail.com > Link: https://lore.kernel.org/all/68e9715a.050a0220.1186a4.000d.GAE@google.com > Debugged-by: Lance Yang > Signed-off-by: Matthew Wilcox (Oracle) > Cc: stable@vger.kernel.org > --- > mm/migrate.c | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > LGTM. Acked-by: Zi Yan Best Regards, Yan, Zi