Re: [PATCH 2/2] mm: fix numa stats for thp migration

[Yang Shi <shy828301@gmail.com>]

On Sun, Dec 27, 2020 at 10:16 AM Shakeel Butt <shakeelb@google.com> wrote:
>
> On Sun, Dec 27, 2020 at 10:14 AM Shakeel Butt <shakeelb@google.com> wrote:
> >
> > Currently the kernel is not correctly updating the numa stats for
> > NR_FILE_PAGES and NR_SHMEM on THP migration. Fix that. For NR_FILE_DIRTY
> > and NR_ZONE_WRITE_PENDING, although at the moment there is no need to
> > handle THP migration as kernel still does not have write support for
> > file THP but to be more future proof, this patch adds the THP support
> > for those stats as well.
> >
> > Fixes: e71769ae52609 ("mm: enable thp migration for shmem thp")
> > Signed-off-by: Shakeel Butt <shakeelb@google.com>
> > Cc: <stable@vger.kernel.org>
> > ---
> >  mm/migrate.c | 23 ++++++++++++-----------
> >  1 file changed, 12 insertions(+), 11 deletions(-)
> >
> > diff --git a/mm/migrate.c b/mm/migrate.c
> > index 613794f6a433..ade163c6ecdf 100644
> > --- a/mm/migrate.c
> > +++ b/mm/migrate.c
> > @@ -402,6 +402,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
> >         struct zone *oldzone, *newzone;
> >         int dirty;
> >         int expected_count = expected_page_refs(mapping, page) + extra_count;
> > +       int nr = thp_nr_pages(page);
> >
> >         if (!mapping) {
> >                 /* Anonymous page without mapping */
> > @@ -437,7 +438,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
> >          */
> >         newpage->index = page->index;
> >         newpage->mapping = page->mapping;
> > -       page_ref_add(newpage, thp_nr_pages(page)); /* add cache reference */
> > +       page_ref_add(newpage, nr); /* add cache reference */
> >         if (PageSwapBacked(page)) {
> >                 __SetPageSwapBacked(newpage);
> >                 if (PageSwapCache(page)) {
> > @@ -459,7 +460,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
> >         if (PageTransHuge(page)) {
> >                 int i;
> >
> > -               for (i = 1; i < HPAGE_PMD_NR; i++) {
> > +               for (i = 1; i < nr; i++) {
> >                         xas_next(&xas);
> >                         xas_store(&xas, newpage);
> >                 }
> > @@ -470,7 +471,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
> >          * to one less reference.
> >          * We know this isn't the last reference.
> >          */
> > -       page_ref_unfreeze(page, expected_count - thp_nr_pages(page));
> > +       page_ref_unfreeze(page, expected_count - nr);
> >
> >         xas_unlock(&xas);
> >         /* Leave irq disabled to prevent preemption while updating stats */
> > @@ -493,17 +494,17 @@ int migrate_page_move_mapping(struct address_space *mapping,
> >                 old_lruvec = mem_cgroup_lruvec(memcg, oldzone->zone_pgdat);
> >                 new_lruvec = mem_cgroup_lruvec(memcg, newzone->zone_pgdat);
> >
> > -               __dec_lruvec_state(old_lruvec, NR_FILE_PAGES);
> > -               __inc_lruvec_state(new_lruvec, NR_FILE_PAGES);
> > +               __mod_lruvec_state(old_lruvec, NR_FILE_PAGES, -nr);
> > +               __mod_lruvec_state(new_lruvec, NR_FILE_PAGES, nr);
> >                 if (PageSwapBacked(page) && !PageSwapCache(page)) {
> > -                       __dec_lruvec_state(old_lruvec, NR_SHMEM);
> > -                       __inc_lruvec_state(new_lruvec, NR_SHMEM);
> > +                       __mod_lruvec_state(old_lruvec, NR_SHMEM, -nr);
> > +                       __mod_lruvec_state(new_lruvec, NR_SHMEM, nr);
> >                 }
> >                 if (dirty && mapping_can_writeback(mapping)) {
> > -                       __dec_lruvec_state(old_lruvec, NR_FILE_DIRTY);
> > -                       __dec_zone_state(oldzone, NR_ZONE_WRITE_PENDING);
> > -                       __inc_lruvec_state(new_lruvec, NR_FILE_DIRTY);
> > -                       __inc_zone_state(newzone, NR_ZONE_WRITE_PENDING);
> > +                       __mod_lruvec_state(old_lruvec, NR_FILE_DIRTY, -nr);
> > +                       __mod_zone_page_tate(oldzone, NR_ZONE_WRITE_PENDING, -nr);
>
> This should be __mod_zone_page_state(). I fixed locally but sent the
> older patch by mistake.

Acked-by: Yang Shi <shy828301@gmail.com>

>
> > +                       __mod_lruvec_state(new_lruvec, NR_FILE_DIRTY, nr);
> > +                       __mod_zone_page_state(newzone, NR_ZONE_WRITE_PENDING, nr);
> >                 }
> >         }
> >         local_irq_enable();
> > --
> > 2.29.2.729.g45daf8777d-goog
> >
>