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Shutemov" , 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: <08ff7961-7e86-40b3-8e25-1592526c94d4@lucifer.local> References: <6b73e692c2929dc4613af711bdf92e2ec1956a66.1682638385.git.lstoakes@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: 68FCFA0012 X-Rspamd-Server: rspam01 X-Stat-Signature: n9iq1xeajeg56n4ioyspp6yz53d77y7u X-HE-Tag: 1682809779-566944 X-HE-Meta: U2FsdGVkX1+QrHJSRB5Y5LlDDEkQ4EFuIb4xjcdssi5abkBn18EftNL9CLPAGrz4ehKhwSv2AlhM7aaZIdv1Tv3iHozqmZFw+D/7J6ZhtWnbK9ApM1GX6Gvqk+5nzvH3TI2H+RCPjWh7awg6wyyY/HNuAnHM737Du7V7Ag+A4tktIFtxwPZVc61aq96wuDLxRoPLlajEoL1eh0fI1SZL/qaeINMxJ5QuDCzdRpGOyzRaZy9hAS3pjd7Rt9RQ+jYRhRClf21VQJww9x2zGY3aNrH51X+KLaVdMQ36u2dckhDhyRsx1g2i7fLA3c6JcdDQyBUhhsZTtjDeAbTmYCgV643CpMbsqksEo5uxUJhPJRXkiFvROZsHByhdDnPYxKJ+nQhIhvGrlwwgs2/xISH+Cuf0xqv06dU4OEKcq8hD6CM/mWLdI5sXFuTFB+PK0kmFhIOEF2RjQKWQpql04HE9vBE6n1/DmndgG23Rj+ZDgjLj2BA/172b8PF3XlAuUzajeGia1pOPS7pKPyCDejOnHO/dQIJ6vAFqRHRAVCp8iQ+mQTXIIGx6hffFR24ob6KVFVTcqxwl1img94bImX89PUAIdpA7kWem1tICtaeb7MlBFLrzpQP5rvhL/MJJ6LD1LlWS4s59LOXxb2Cxg3E0sUw3FRNOyH1mRc3CzT3eaWskyC39cS1r1BEt3p4t18/SemVvJFEVE/PI9cWOYZEWHz1I8uRJHRTkyRXjqKXNaR6MIC9l3frlX34peQ3Uhqs3t23rBctFyOkZI33UzZZh87riVdTlLs4M8/VEdg0HWUaErLZk+hWrIRPeDO87jkyZL/u/qe35TFj1QW4CscnEkPyPYZCe4GOP8e+ysqyaA/bDxmc5lb7cxcjlGetUPAWby8DAngD/pYnTYCD4PLFWwWkhfQ5r0V7EwiMz6I/H5gd6xup2WGM0lHvcAMnJ6vpH7P5jMzWp1LSSuYEAbcO DDRkq6Rt AdfXBtvuGopDdXG20qlcQrnupHpksGMlWh0QkeYVH5u2tXKAIiXLVhDZZck4FN3CdY6vB+2TzDyq+k22l+Ot7xv8O70r6K07CKwWLkpM4+6+ryB329udzsD7iPL4JD0bD2ftOjj9Q6sXokVydB0xbM0d+ZwNOQHK18wuLUM3i6BTINUNwgx71SYbZkelWXx6om8I6H1LcsS3FN0xRCnHHxaDXQ9KELh0K2v7COjATuscKFSsoxNxlybpSe40x0CbkVM5fLNVL8dk88MsE2RjBaV+EUvdJZazO1gem8KYeKdzUXnbvYpYf7JMU8F01CYX+2ZOcn0tsJ/djX4wR2Y42tetXeMgcxFJw20DJG4ycQWsifE2vJMvSr8VzeCF6JL7R4QH69ScxFZUpQgTBNgeMun9iVExFNez63Gpe7YAfFgoYxgj6lFe8EBfdbe9+vm+F7bluICGKuji1hIap73QSRQHJzg== 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 Sat, Apr 29, 2023 at 08:01:11PM -0300, Jason Gunthorpe wrote: > On Sat, Apr 29, 2023 at 12:21:09AM -0400, Theodore Ts'o wrote: > > > In any case, the file system maintainers' position (mine and I doubt > > Dave Chinner's position has changed) is that if you write to > > file-backed mappings via GUP/RDMA/process_vm_writev, and it causes > > silent data corruption, you get to keep both pieces, and don't go > > looking for us for anything other than sympathy... > > This alone is enough reason to block it. I'm tired of this round and > round and I think we should just say enough, the mm will work to > enforce this view point. Files can only be written through PTEs. > > If this upsets people they can work on fixing it, but at least we > don't have these kernel problems and inconsistencies to deal with. > Indeed, I think there is a broad consensus that FOLL_LONGTERM is such an egregious case that this is the way forward. I will respin with the discussed GUP-fast changes relatively soon and then we can see where that takes us :) > Jason