On Fri, Jan 17, 2025 at 04:29:47PM +0000, 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)) {
I think you need:
+#if IS_ENABLED(CONFIG_HUGETLBFS)
> + case PGTY_hugetlb:
> + free_huge_folio(folio);
> + return;
+#endif
I think this worked before because folio_test_hugetlb was defined by:
FOLIO_TEST_FLAG_FALSE(hugetlb)
and evidently compiler optimizes out the free_huge_folio(folio) before
linking.
You'll probably want to do the same for the PGTY_guestmem in the later
patch!
> + case PGTY_offline:
> + /* Nothing to do, it's offline. */
> + return;
> + default:
> + WARN_ON_ONCE(1);
> + }
> +}
> +
> void __folio_put(struct folio *folio)
> {
> if (unlikely(folio_is_zone_device(folio))) {
> @@ -101,8 +115,8 @@ void __folio_put(struct folio *folio)
> return;
> }
>
> - if (folio_test_hugetlb(folio)) {
> - free_huge_folio(folio);
> + if (unlikely(folio_has_type(folio))) {
> + free_typed_folio(folio);
> return;
> }
>
> @@ -934,13 +948,13 @@ void folios_put_refs(struct folio_batch *folios, unsigned int *refs)
> if (!folio_ref_sub_and_test(folio, nr_refs))
> continue;
>
> - /* hugetlb has its own memcg */
> - if (folio_test_hugetlb(folio)) {
> + if (unlikely(folio_has_type(folio))) {
> + /* typed folios have their own memcg, if any */
> if (lruvec) {
> unlock_page_lruvec_irqrestore(lruvec, flags);
> lruvec = NULL;
> }
> - free_huge_folio(folio);
> + free_typed_folio(folio);
> continue;
> }
> folio_unqueue_deferred_split(folio);
> --
> 2.48.0.rc2.279.g1de40edade-goog
>
