Re: [External] Re: [PATCH] mm: migrate: fix missing update page_private to hugetlb_page_subpool

[Muchun Song <songmuchun@bytedance.com>]

On Thu, May 20, 2021 at 12:24 PM Andrew Morton
<akpm@linux-foundation.org> wrote:
>
> On Thu, 20 May 2021 10:59:49 +0800 Muchun Song <songmuchun@bytedance.com> wrote:
>
> > Since commit d6995da31122 ("hugetlb: use page.private for hugetlb specific
> > page flags") converts page.private for hugetlb specific page flags. We
> > should use hugetlb_page_subpool() to get the subpool pointer instead of
> > page_private(). The commit forgot to update it in the page migration
> > routine. So fix it.
> >
> > ...
> >
> > --- a/mm/migrate.c
> > +++ b/mm/migrate.c
> > @@ -1290,7 +1290,7 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
> >        * page_mapping() set, hugetlbfs specific move page routine will not
> >        * be called and we could leak usage counts for subpools.
> >        */
> > -     if (page_private(hpage) && !page_mapping(hpage)) {
> > +     if (hugetlb_page_subpool(hpage) && !page_mapping(hpage)) {
> >               rc = -EBUSY;
> >               goto out_unlock;
> >       }
>
> So it uses the wrong page*, so this isn't just a cosmetic fix.  One
> cannot tell from this changelog.
>
> Please describe the runtime effects of this bug.  Please always include
> this information when fixing bugs.  And when adding them.

OK. I should update the commit log in the next version.

Thanks.