Re: [PATCH v3 00/23] mm/gup: track dma-pinned pages: FOLL_PIN, FOLL_LONGTERM

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On 11/13/19 3:43 AM, Daniel Vetter wrote:
...
Can't we call this unpin_user_page then, for some symmetry? Or is that
even more churn?

Looking from afar the naming here seems really confusing.


That look from afar is valuable, because I'm too close to the problem to see
how the naming looks. :)

unpin_user_page() sounds symmetrical. It's true that it would cause more
churn (which is why I started off with a proposal that avoids changing the
names of put_user_page*() APIs). But OTOH, the amount of churn is proportional
to the change in direction here, and it's really only 10 or 20 lines changed,
in the end.

So I'm open to changing to that naming. It would be nice to hear what others
prefer, too...

FWIW I'd find unpin_user_page() also better than put_user_page() as a
counterpart to pin_user_pages().

One more point from afar on pin/unpin: We use that a lot in graphics for
permanently pinned graphics buffer objects. Which really only should be
used for scanout. So at least graphics folks should have an appropriate
mindset and try to make sure we don't overuse this stuff.
-Daniel


OK, Ira also likes "unpin", and so far no one has said *anything* in favor
of the "put_user_page" names, so I think we have a winner! I'll change the
names to unpin_user_page*().


thanks,
--
John Hubbard
NVIDIA



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