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Shutemov" , stable@vger.kernel.org Subject: Re: [PATCH v1 1/2] mm/hugetlb: fix hugetlb not supporting write-notify Message-ID: References: <20220805110329.80540-1-david@redhat.com> <20220805110329.80540-2-david@redhat.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: MW2PR2101CA0031.namprd21.prod.outlook.com (2603:10b6:302:1::44) To BY5PR10MB4196.namprd10.prod.outlook.com (2603:10b6:a03:20d::23) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 5c60ae9d-1499-465a-d9e2-08da7711012b X-MS-TrafficTypeDiagnostic: MWHPR10MB1328:EE_ X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BY5PR10MB4196.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230016)(7916004)(136003)(366004)(346002)(39860400002)(376002)(396003)(41300700001)(6666004)(2906002)(6506007)(6512007)(53546011)(26005)(9686003)(186003)(38100700002)(33716001)(5660300002)(86362001)(316002)(54906003)(8936002)(6916009)(6486002)(478600001)(8676002)(44832011)(66556008)(66476007)(66946007)(4326008);DIR:OUT;SFP:1101; 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> >>> > >>> + /* > >>> + * Hugetlb does not require/support writenotify; especially, it does not > >>> + * support softdirty tracking. > >>> + */ > >>> + if (is_vm_hugetlb_page(vma)) > >>> + return 0; > >> > >> I'm kind of confused here.. you seems to be fixing up soft-dirty for > >> hugetlb but here it's explicitly forbidden. > >> > >> Could you explain a bit more on why this patch is needed if (assume > >> there'll be a working) patch 2 being provided? > >> > > > > No comments on the patch, but ... > > > > Since it required little thought, I ran the test program on next-20220802 and > > was surprised that the issue did not recreate. Even added a simple printk > > to make sure we were getting into vma_wants_writenotify with a hugetlb vma. > > We were. > > > ... does your config have CONFIG_MEM_SOFT_DIRTY enabled? > No, Duh! FYI - Some time back, I started looking at adding soft dirty support for hugetlb mappings. I did not finish that work. But, I seem to recall places where code was operating on hugetlb mappings when perhaps it should not. Perhaps, it would also be good to just disable soft dirty for hugetlb at the source? -- Mike Kravetz