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See http://www.infradead.org/rpr.html X-Rspamd-Queue-Id: 9ECAB140008 X-Stat-Signature: mads3d3tz9tyru4iq4umkqcz1tr7hmtb X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1676874159-647488 X-HE-Meta: U2FsdGVkX1/m4Sq2EPbnKDlxwhLmGt22c5qD5wkjhjPqB3rR7N3B2BgvgU6tX5COaDVlx+sm1a2TUQmZzEEr8m3KTYLylqB+19RIwCBgHD5POaBmMAge+y5Rx89TkX49Qz4qLkq2yGdMVjVZ50HZsu87U9d5d2jOv/ZtrhEEvLv+OWBV0w5szfbIJHGHb4G8jyXgPPOhKjyWyKb+ZLGV+ZlVRxyXluZ1YtjwPXnryXo9Ey1ZJCqbPFE4t175AMrbqRxdsG41ITdTkyRmGjVllWtychH46Ona7S/D+F4k0VM0cMJbbBZNOirKo+MgiX+X84hPkPoIukp3IalipGUUz5W9EcI0RFdwyDy4B5k8RzqmOv/CgM9lDKynRoxuhvcnit2jO7XGkpW5wqnO5bhBilhdqVOCxw0Lv7CJr0P5Nj7duyl2TQrlXNCOe/tylrJd6G8fcC2kuoq716knZ9f7cZD4dqB5pXzQRHZYxLpzkqJ0bH759qZd2njFIXwYlM/VkLCckTGFi0Lp/1d8fPKFcEYklkzb52qldoqokUpObP+OBayFlIGI7hDPCiwT5jSAAkFlWwL7WMGZNSqV00fRgQKY2Fr7Y/QWcb2srUCx8nyo4Ghyo69Ql627Twqa7K3WrhFVaDtrYJLcmjxY6M6As/9UQpFNbsftYrOH+6IYkUuRLqbdudAfY4LzapUY8QVReGaIWOL6Qf/FtbUeilk5uqnkxoBVZnXGLjgwlWxpj4yW4TH9hl2SSEv1m6P8anLmy+Jmj0dB6aIZczImOWlvQPTXuTicphRxmj+60A1ZP0qAP3i8tquF/qKc5d7K0lSbSD6Ewm3LyiblYRl80yseT0p/AaLUVYYoRCv08D5pcPNWWU8Zyj0Iyti3QR6wgFkHSUOo4k2VkCmVtxmoVGp8NbRZTDVDHg/g3Xwxe2dndee6knp3PBpCHTiY6lp8BRPKrs+/UawYNYvqN9kw4tp fzlQZwA2 Y2j8E0B1V8TxQXpSFgJrahcHosmgmmkCOF3vOg2/SXnc9HwD93+caCbfn2wR2YiK/Vh2Dv8jIRimYBiraMqSR3SnsCRq5AMb/8ijK+ywgsMwR2HYmLmcvwoT7DLjtEFFun/cYYE345IkH7rU1b3vzzIapmoNi6q4BWUQ6TQWedyTkdRXsl6RavQBkC+CW6tY8uSCwArVDC7QttCTCinAUGQ0gN7qa8IHc8pywIdPO1gviy7lLjV8zCwtE6ftA9TFQJdNAgurqp/PWlci8F96AiNeWJBJvdGRl/G3Y4P/x01P4op6cPSgbsqReGSC+DnO3bFzNr2UhLGr39X4i4ApbcnJT+P3Y9sqEMZwg1CY/RjPYhWi8pUTq5SN12247LAheqzZDiy65vdK+6ysIbzp72Gey8Q== 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 Thu, Feb 16, 2023 at 01:33:16PM +0100, Jan Kara wrote: > I'm a bit skeptical we can reasonably assess that (as much as I would love > to just not write these pages and be done with it) because a lot of > FOLL_LONGTERM users just pin passed userspace address range, then allow > userspace to manipulate it with other operations, and finally unpin it with > another call. Who knows whether shared pagecache pages are passed in and > what userspace is doing with them while they are pinned? True. So what other sensible thing could we do at a higher level? Treat MAP_SHARED buffers that are long term registered as MAP_PRIVATE while registered, and just do writeback using in-kernel O_DIRECT on fsync?