On Mon, 20 Jan 2025 at 10:39, David Hildenbrand <david@xxxxxxxxxx> wrote:
>
> On 17.01.25 17:29, Fuad Tabba wrote:
> > Some folio types, such as hugetlb, handle freeing their own
> > folios. Moreover, guest_memfd will require being notified once a
> > folio's reference count reaches 0 to facilitate shared to private
> > folio conversion, without the folio actually being freed at that
> > point.
> >
> > As a first step towards that, this patch consolidates freeing
> > folios that have a type. The first user is hugetlb folios. Later
> > in this patch series, guest_memfd will become the second user of
> > this.
> >
> > Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
> > Signed-off-by: Fuad Tabba <tabba@xxxxxxxxxx>
> > ---
> > include/linux/page-flags.h | 15 +++++++++++++++
> > mm/swap.c | 24 +++++++++++++++++++-----
> > 2 files changed, 34 insertions(+), 5 deletions(-)
> >
> > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> > index 691506bdf2c5..6615f2f59144 100644
> > --- a/include/linux/page-flags.h
> > +++ b/include/linux/page-flags.h
> > @@ -962,6 +962,21 @@ static inline bool page_has_type(const struct page *page)
> > return page_mapcount_is_type(data_race(page->page_type));
> > }
> >
> > +static inline int page_get_type(const struct page *page)
> > +{
> > + return page->page_type >> 24;
> > +}
> > +
> > +static inline bool folio_has_type(const struct folio *folio)
> > +{
> > + return page_has_type(&folio->page);
> > +}
> > +
> > +static inline int folio_get_type(const struct folio *folio)
> > +{
> > + return page_get_type(&folio->page);
> > +}
> > +
> > #define FOLIO_TYPE_OPS(lname, fname) \
> > static __always_inline bool folio_test_##fname(const struct folio *folio) \
> > { \
> > diff --git a/mm/swap.c b/mm/swap.c
> > index 10decd9dffa1..6f01b56bce13 100644
> > --- a/mm/swap.c
> > +++ b/mm/swap.c
> > @@ -94,6 +94,20 @@ static void page_cache_release(struct folio *folio)
> > unlock_page_lruvec_irqrestore(lruvec, flags);
> > }
> >
> > +static void free_typed_folio(struct folio *folio)
> > +{
> > + switch (folio_get_type(folio)) {
> > + case PGTY_hugetlb:
> > + free_huge_folio(folio);
> > + return;
> > + case PGTY_offline:
> > + /* Nothing to do, it's offline. */
> > + return;
>
> Please drop the PGTY_offline part for now, it was rather to highlight
> what could be done.
Will do.
Thanks,
/fuad
>
> But the real goal will be to not make offline pages
> use the refcount at all (frozen).
>
> If we really want the temporary PGTY_offline change, it should be
> introduced separately.
>
> Apart from that LGTM!
>
> --
> Cheers,
>
> David / dhildenb
>
