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charset="UTF-8" X-Rspamd-Queue-Id: DF908A0006 X-Stat-Signature: y7i91u578351k8uzszant84kgz8rnrf8 X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1684390111-400385 X-HE-Meta: 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 tQPZrBvP aI56eoEEhZvKB0oFGTntytjz39jdstQmOp1jlGoLyOHAuVg3haQS963ps6GQ6PtWlrJbPwRUHF/rP99d2lwIRTbTlytMb8L3CYIDAHXmj+Co/5tfEspFl5v/QQlMSp3hEco6PFsENy1gEGsdOlb/yaCc8aTGWbmDHUqxeyar7Aw93rKFJnv5R2Bw9dc2nIsXRroyKf0WhTJOvtJeMJqKeCPUcKpqHO2Gyg4z9/Ge790YwDRzrfL+BPjzIncKIN4vWeMS399KnBEVLb7GgtqYD2yjI8kVBvuOBx/Nng23+pk0kDxAswfp00GKIcuxkKPcvmmLDNgFvq7YXqJ5uQVrZGmhgOSeuRyXHeMY/iESc207veCC1pCjmU7+VSC7Y2S5lvDjidQll5DevmS3axiGnfCB7Pg== 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, 18 May 2023 at 09:51, Christoph Hellwig wrote: > > On Wed, May 17, 2023 at 08:23:33PM +0200, David Hildenbrand wrote: > > In general: if user space controls it -> possibly forever -> long-term. Even > > if in most cases it's a short delay: there is no trusting on user space. > > > > For example, iouring fixed buffers keep pages pinned until user space > > decides to unregistered the buffers -> long-term. > > > > Short-term is, for example, something like O_DIRECT where we pin -> DMA -> > > unpin in essentially one operation. > > Btw, one thing that's been on my mind is that I think we got the > polarity on FOLL_LONGTERM wrong. Instead of opting into the long term > behavior it really should be the default, with a FOLL_EPHEMERAL flag > to opt out of it. And every users of this flag is required to have > a comment explaining the life time rules for the pin.. It does look like a better approach to me given the very nature of user space pages. -Sumit