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Shutemov" , Peter Xu , Lorenzo Stoakes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Jens Axboe , Matthew Wilcox , Dennis Dalessandro , Leon Romanovsky , Christian Benvenuti , Nelson Escobar , Bernard Metzler , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Ian Rogers , Adrian Hunter , Bjorn Topel , Magnus Karlsson , Maciej Fijalkowski , Jonathan Lemon , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Christian Brauner , Richard Cochran , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , linux-fsdevel@vger.kernel.org, linux-perf-users@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, Oleg Nesterov , John Hubbard , Jan Kara , Pavel Begunkov , Mika Penttila , David Howells , Christoph Hellwig Subject: Re: [PATCH v5] mm/gup: disallow GUP writing to file-backed mappings by default Message-ID: References: <077c4b21-8806-455f-be98-d7052a584259@lucifer.local> <62ec50da-5f73-559c-c4b3-bde4eb215e08@redhat.com> <6ddc7ac4-4091-632a-7b2c-df2005438ec4@redhat.com> <20230428160925.5medjfxkyvmzfyhq@box.shutemov.name> <39cc0f26-8fc2-79dd-2e84-62238d27fd98@redhat.com> <20230428162207.o3ejmcz7rzezpt6n@box.shutemov.name> <173337c0-14f4-3246-15ff-7fbf03861c94@redhat.com> <20230428165623.pqchgi5gtfhxd5b5@box.shutemov.name> <1039c830-acec-d99b-b315-c2a6e26c34ca@redhat.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1039c830-acec-d99b-b315-c2a6e26c34ca@redhat.com> X-ClientProxiedBy: MN2PR06CA0021.namprd06.prod.outlook.com (2603:10b6:208:23d::26) To LV2PR12MB5869.namprd12.prod.outlook.com (2603:10b6:408:176::16) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV2PR12MB5869:EE_|MW3PR12MB4572:EE_ X-MS-Office365-Filtering-Correlation-Id: 825fa88c-3a99-4e9f-47dc-08db480e6c5c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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And > > TLB flushing is serialized against GUP_fast(). > > The whole CONFIG_MMU_GATHER_RCU_TABLE_FREE handling makes the situation more > complicated. Yeah, you have to think of gup_fast as RCU with a hacky pre-RCU implementation on most architectures. We could make page->mapping safe under RCU, for instance. Jason