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See http://www.infradead.org/rpr.html X-Rspamd-Queue-Id: 4452440008 X-Stat-Signature: d5kutth8e6dmea3a7agaicwtc1szdex5 X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1684383669-165751 X-HE-Meta: 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 OxWwiy86 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 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 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..