Re: [RESEND 1/7] mm/gup: Replace get_user_pages_longterm() with FOLL_LONGTERM

Ira Weiny
2019-03-25T08:46:14Z

On Mon, Mar 25, 2019 at 09:45:12AM -0700, Dan Williams wrote:
> On Mon, Mar 25, 2019 at 7:21 AM Ira Weiny <ira.weiny@intel.com> wrote:
> [..]
> > > > @@ -1268,10 +1246,14 @@ static long check_and_migrate_cma_pages(unsigned long start, long nr_pages,
> > > > putback_movable_pages(&cma_page_list);
> > > > }
> > > > /*
> > > > - * We did migrate all the pages, Try to get the page references again
> > > > - * migrating any new CMA pages which we failed to isolate earlier.
> > > > + * We did migrate all the pages, Try to get the page references
> > > > + * again migrating any new CMA pages which we failed to isolate
> > > > + * earlier.
> > > > */
> > > > - nr_pages = get_user_pages(start, nr_pages, gup_flags, pages, vmas);
> > > > + nr_pages = __get_user_pages_locked(tsk, mm, start, nr_pages,
> > > > + pages, vmas, NULL,
> > > > + gup_flags);
> > > > +
> > >
> > > Why did this need to change to __get_user_pages_locked?
> >
> > __get_uer_pages_locked() is now the "internal call" for get_user_pages.
> >
> > Technically it did not _have_ to change but there is no need to call
> > get_user_pages() again because the FOLL_TOUCH flags is already set. Also this
> > call then matches the __get_user_pages_locked() which was called on the pages
> > we migrated from. Mostly this keeps the code "symmetrical" in that we called
> > __get_user_pages_locked() on the pages we are migrating from and the same call
> > on the pages we migrated to.
> >
> > While the change here looks funny I think the final code is better.
>
> Agree, but I think that either needs to be noted in the changelog so
> it's not a surprise, or moved to a follow-on cleanup patch.
>

Can do...

Thanks!
Ira