[PATCH 4/5] mm: Add PageAnonNotKsm()

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

Check that this anonymous page is really anonymous, not
anonymous-or-KSM.  This optimises the debug check, but its real purpose
is to remove the last two users of PageKsm().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/page-flags.h | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 4c2dfe289046..157c4ffc2fdc 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -689,6 +689,13 @@ static __always_inline bool folio_test_anon(const struct folio *folio)
 	return ((unsigned long)folio->mapping & PAGE_MAPPING_ANON) != 0;
 }
 
+static __always_inline bool PageAnonNotKsm(const struct page *page)
+{
+	unsigned long flags = (unsigned long)page_folio(page)->mapping;
+
+	return (flags & PAGE_MAPPING_FLAGS) == PAGE_MAPPING_ANON;
+}
+
 static __always_inline bool PageAnon(const struct page *page)
 {
 	return folio_test_anon(page_folio(page));
@@ -1129,14 +1136,14 @@ static __always_inline int PageAnonExclusive(const struct page *page)
 
 static __always_inline void SetPageAnonExclusive(struct page *page)
 {
-	VM_BUG_ON_PGFLAGS(!PageAnon(page) || PageKsm(page), page);
+	VM_BUG_ON_PGFLAGS(PageAnonNotKsm(page), page);
 	VM_BUG_ON_PGFLAGS(PageHuge(page) && !PageHead(page), page);
 	set_bit(PG_anon_exclusive, &PF_ANY(page, 1)->flags);
 }
 
 static __always_inline void ClearPageAnonExclusive(struct page *page)
 {
-	VM_BUG_ON_PGFLAGS(!PageAnon(page) || PageKsm(page), page);
+	VM_BUG_ON_PGFLAGS(PageAnonNotKsm(page), page);
 	VM_BUG_ON_PGFLAGS(PageHuge(page) && !PageHead(page), page);
 	clear_bit(PG_anon_exclusive, &PF_ANY(page, 1)->flags);
 }
-- 
2.43.0