On Mon, Jun 30, 2025 at 03:00:01PM +0200, David Hildenbrand wrote: > Instead, let's use a page flag. As the page flag can result in > false-positives, glue it to the page types for which we > support/implement movable_ops page migration. > > The flag reused by PageMovableOps() might be sued by other pages, so
I assume 'used' not 'sued' :P > warning in case it is set in page_has_movable_ops() might result in > false-positive warnings. Worth mentioning that it's PG_uptodate. Also probably worth putting a proviso here that we're safe to use it for movable ops pages because it's used to track file system state. > > Reviewed-by: Zi Yan <z...@nvidia.com> > Signed-off-by: David Hildenbrand <da...@redhat.com> Seems reasonable though, so: Reviewed-by: Lorenzo Stoakes <lorenzo.stoa...@oracle.com> > --- > include/linux/balloon_compaction.h | 2 +- > include/linux/migrate.h | 8 ----- > include/linux/page-flags.h | 52 ++++++++++++++++++++++++------ > mm/compaction.c | 6 ---- > mm/zpdesc.h | 2 +- > 5 files changed, 44 insertions(+), 26 deletions(-) > > diff --git a/include/linux/balloon_compaction.h > b/include/linux/balloon_compaction.h > index a8a1706cc56f3..b222b0737c466 100644 > --- a/include/linux/balloon_compaction.h > +++ b/include/linux/balloon_compaction.h > @@ -92,7 +92,7 @@ static inline void balloon_page_insert(struct > balloon_dev_info *balloon, > struct page *page) > { > __SetPageOffline(page); > - __SetPageMovable(page); > + SetPageMovableOps(page); > set_page_private(page, (unsigned long)balloon); > list_add(&page->lru, &balloon->pages); > } > diff --git a/include/linux/migrate.h b/include/linux/migrate.h > index 6aece3f3c8be8..acadd41e0b5cf 100644 > --- a/include/linux/migrate.h > +++ b/include/linux/migrate.h > @@ -103,14 +103,6 @@ static inline int migrate_huge_page_move_mapping(struct > address_space *mapping, > > #endif /* CONFIG_MIGRATION */ > > -#ifdef CONFIG_COMPACTION > -void __SetPageMovable(struct page *page); > -#else > -static inline void __SetPageMovable(struct page *page) > -{ > -} > -#endif > - > #ifdef CONFIG_NUMA_BALANCING > int migrate_misplaced_folio_prepare(struct folio *folio, > struct vm_area_struct *vma, int node); > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index 4c27ebb689e3c..016a6e6fa428a 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -170,6 +170,11 @@ enum pageflags { > /* non-lru isolated movable page */ > PG_isolated = PG_reclaim, > > +#ifdef CONFIG_MIGRATION > + /* this is a movable_ops page (for selected typed pages only) */ > + PG_movable_ops = PG_uptodate, > +#endif > + > /* Only valid for buddy pages. Used to track pages that are reported */ > PG_reported = PG_uptodate, > > @@ -698,9 +703,6 @@ PAGEFLAG_FALSE(VmemmapSelfHosted, vmemmap_self_hosted) > * bit; and then folio->mapping points, not to an anon_vma, but to a private > * structure which KSM associates with that merged page. See ksm.h. > * > - * PAGE_MAPPING_KSM without PAGE_MAPPING_ANON is used for non-lru movable > - * page and then folio->mapping points to a struct movable_operations. > - * > * Please note that, confusingly, "folio_mapping" refers to the inode > * address_space which maps the folio from disk; whereas "folio_mapped" > * refers to user virtual address space into which the folio is mapped. > @@ -743,13 +745,6 @@ static __always_inline bool PageAnon(const struct page > *page) > { > return folio_test_anon(page_folio(page)); > } > - > -static __always_inline bool page_has_movable_ops(const struct page *page) > -{ > - return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) == > - PAGE_MAPPING_MOVABLE; > -} > - > #ifdef CONFIG_KSM > /* > * A KSM page is one of those write-protected "shared pages" or "merged > pages" > @@ -1133,6 +1128,43 @@ bool is_free_buddy_page(const struct page *page); > > PAGEFLAG(Isolated, isolated, PF_ANY); > > +#ifdef CONFIG_MIGRATION > +/* > + * This page is migratable through movable_ops (for selected typed pages > + * only). > + * > + * Page migration of such pages might fail, for example, if the page is > + * already isolated by somebody else, or if the page is about to get freed. > + * > + * While a subsystem might set selected typed pages that support page > migration > + * as being movable through movable_ops, it must never clear this flag. > + * > + * This flag is only cleared when the page is freed back to the buddy. > + * > + * Only selected page types support this flag (see page_movable_ops()) and > + * the flag might be used in other context for other pages. Always use > + * page_has_movable_ops() instead. > + */ > +PAGEFLAG(MovableOps, movable_ops, PF_NO_TAIL); > +#else > +PAGEFLAG_FALSE(MovableOps, movable_ops); > +#endif > + > +/** > + * page_has_movable_ops - test for a movable_ops page > + * @page The page to test. > + * > + * Test whether this is a movable_ops page. Such pages will stay that > + * way until freed. > + * > + * Returns true if this is a movable_ops page, otherwise false. > + */ > +static inline bool page_has_movable_ops(const struct page *page) > +{ > + return PageMovableOps(page) && > + (PageOffline(page) || PageZsmalloc(page)); > +} > + > static __always_inline int PageAnonExclusive(const struct page *page) > { > VM_BUG_ON_PGFLAGS(!PageAnon(page), page); > diff --git a/mm/compaction.c b/mm/compaction.c > index 348eb754cb227..349f4ea0ec3e5 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -114,12 +114,6 @@ static unsigned long release_free_list(struct list_head > *freepages) > } > > #ifdef CONFIG_COMPACTION > -void __SetPageMovable(struct page *page) > -{ > - VM_BUG_ON_PAGE(!PageLocked(page), page); > - page->mapping = (void *)(PAGE_MAPPING_MOVABLE); > -} > -EXPORT_SYMBOL(__SetPageMovable); > > /* Do not skip compaction more than 64 times */ > #define COMPACT_MAX_DEFER_SHIFT 6 > diff --git a/mm/zpdesc.h b/mm/zpdesc.h > index 6855d9e2732d8..25bf5ea0beb83 100644 > --- a/mm/zpdesc.h > +++ b/mm/zpdesc.h > @@ -154,7 +154,7 @@ static inline struct zpdesc *pfn_zpdesc(unsigned long pfn) > > static inline void __zpdesc_set_movable(struct zpdesc *zpdesc) > { > - __SetPageMovable(zpdesc_page(zpdesc)); > + SetPageMovableOps(zpdesc_page(zpdesc)); > } > > static inline void __zpdesc_set_zsmalloc(struct zpdesc *zpdesc) > -- > 2.49.0 >