On Tue, Nov 12, 2019 at 10:10 PM John Hubbard <jhubbard@xxxxxxxxxx> wrote: > > On 11/12/19 12:38 PM, Jason Gunthorpe wrote: > > On Mon, Nov 11, 2019 at 04:06:37PM -0800, John Hubbard wrote: > >> Hi, > >> > >> The cover letter is long, so the more important stuff is first: > >> > >> * Jason, if you or someone could look at the the VFIO cleanup (patch 8) > >> and conversion to FOLL_PIN (patch 18), to make sure it's use of > >> remote and longterm gup matches what we discussed during the review > >> of v2, I'd appreciate it. > >> > >> * Also for Jason and IB: as noted below, in patch 11, I am (too?) boldly > >> converting from put_user_pages() to release_pages(). > > > > Why are we doing this? I think things got confused here someplace, as > > > Because: > > a) These need put_page() calls, and > > b) there is no put_pages() call, but there is a release_pages() call that > is, arguably, what put_pages() would be. > > > > the comment still says: > > > > /** > > * put_user_page() - release a gup-pinned page > > * @page: pointer to page to be released > > * > > * Pages that were pinned via get_user_pages*() must be released via > > * either put_user_page(), or one of the put_user_pages*() routines > > * below. > > > Ohhh, I missed those comments. They need to all be changed over to > say "pages that were pinned via pin_user_pages*() or > pin_longterm_pages*() must be released via put_user_page*()." > > The get_user_pages*() pages must still be released via put_page. > > The churn is due to a fairly significant change in strategy, whis > is: instead of changing all get_user_pages*() sites to call > put_user_page(), change selected sites to call pin_user_pages*() or > pin_longterm_pages*(), plus put_user_page(). 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. -Daniel > That allows incrementally converting the kernel over to using the > new pin APIs, without taking on the huge risk of a big one-shot > conversion. > > So, I've ended up with one place that actually needs to get reverted > back to get_user_pages(), and that's the IB ODP code. > > > > > I feel like if put_user_pages() is not the correct way to undo > > get_user_pages() then it needs to be deleted. > > > > Yes, you're right. I'll fix the put_user_page comments() as described. > > > thanks, > > John Hubbard > NVIDIA -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch
