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Mon, 15 May 2023 04:31:53 -0700 (PDT) Date: Mon, 15 May 2023 12:31:51 +0100 From: Lorenzo Stoakes To: Christoph Hellwig Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Jason Gunthorpe , 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 , Jason Gunthorpe , John Hubbard , Jan Kara , "Kirill A . Shutemov" , Pavel Begunkov , Mika Penttila , David Hildenbrand , Dave Chinner , Theodore Ts'o , Peter Xu , Matthew Rosato , "Paul E . McKenney" , Christian Borntraeger Subject: Re: [PATCH v9 0/3] mm/gup: disallow GUP writing to file-backed mappings by default Message-ID: <59c47ed5-a565-4220-823c-a278130092d5@lucifer.local> References: <0eb31f6f-a122-4a5b-a959-03ed4dee1f3c@lucifer.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: j4dz8qdqohf9ump9j7gki87xqaijduoi X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: E8E2AC0004 X-HE-Tag: 1684150315-762724 X-HE-Meta: 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 AejrsjEU dVCZKymgJnm9jETuknKzluACa0l1h3cy53ptgov9LqpvJ7c3zdf2Q4j6w7VnFnmdAfPJkLh320mWxYvCqBV2YkRj8XUgBLWDOdwCB6VLXD8JkkQ9gRVC0fkC6FYE9kPzwo8RkoB6MqmPa9WXSo1TcE0zZc38xGUznUdj5NV7cGfNz0eInCKvcnGqKGRESdoOBwauP00nM5XXBI++JwLA98exwdmsWDz06t/SBYNXGNVJ6Tof8O+CMHvbo6qf2G4opETK10Tqi0CJgfGlLaJxk2U2qcwJsIvGJGPXZ8EE8YFVXWB1WaFFFVRENLLqNkXANjhT+cWWZbDxMZHWaghhmg9ib17OwV763uG/XIhpFxd0exXqI/lZ83ALkAwyHLfr1azfkXKNDBMdDWskjka1InY9D+RhfGQEMjqfHvSEHRWJX6v8AU/W7SwyWvAQN3zIUu1ko6Ynr5yUPDHg= 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: On Sun, May 14, 2023 at 10:14:46PM -0700, Christoph Hellwig wrote: > On Sun, May 14, 2023 at 08:20:04PM +0100, Lorenzo Stoakes wrote: > > As discussed at LSF/MM, on the flight over I wrote a little repro [0] which > > reliably triggers the ext4 warning by recreating the scenario described > > above, using a small userland program and kernel module. > > > > This code is not perfect (plane code :) but does seem to do the job > > adequately, also obviously this should only be run in a VM environment > > where data loss is acceptable (in my case a small qemu instance). > > It would be really awesome if you could wire it up with and submit it > to xfstests. Sure am happy to take a look at that! Also happy if David finds it useful in any way for this unit tests. The kernel module interface is a bit sketchy (it takes a user address which it blindly pins for you) so it's not something that should be run in any unsafe environment but as long as we are ok with that :)