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

John Hubbard
2019-11-13T20:31:05Z

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