mm: constify more page/folio tests

Constify the flag tests that aren't automatically generated and the tests
that look like flag tests but are more complicated.

Link: https://lkml.kernel.org/r/20240227192337.757313-8-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/page-flags.h

@@ -558,13 +558,13 @@ PAGEFLAG_FALSE(HighMem, highmem)
 #endif
 
 #ifdef CONFIG_SWAP
-static __always_inline bool folio_test_swapcache(struct folio *folio)
+static __always_inline bool folio_test_swapcache(const struct folio *folio)
 {
 	return folio_test_swapbacked(folio) &&
-			test_bit(PG_swapcache, folio_flags(folio, 0));
+			test_bit(PG_swapcache, const_folio_flags(folio, 0));
 }
 
-static __always_inline bool PageSwapCache(struct page *page)
+static __always_inline bool PageSwapCache(const struct page *page)
 {
 	return folio_test_swapcache(page_folio(page));
 }
@@ -663,22 +663,22 @@ PAGEFLAG_FALSE(VmemmapSelfHosted, vmemmap_self_hosted)
  */
 #define PAGE_MAPPING_DAX_SHARED	((void *)0x1)
 
-static __always_inline bool folio_mapping_flags(struct folio *folio)
+static __always_inline bool folio_mapping_flags(const struct folio *folio)
 {
 	return ((unsigned long)folio->mapping & PAGE_MAPPING_FLAGS) != 0;
 }
 
-static __always_inline int PageMappingFlags(struct page *page)
+static __always_inline int PageMappingFlags(const struct page *page)
 {
 	return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) != 0;
 }
 
-static __always_inline bool folio_test_anon(struct folio *folio)
+static __always_inline bool folio_test_anon(const struct folio *folio)
 {
 	return ((unsigned long)folio->mapping & PAGE_MAPPING_ANON) != 0;
 }
 
-static __always_inline bool PageAnon(struct page *page)
+static __always_inline bool PageAnon(const struct page *page)
 {
 	return folio_test_anon(page_folio(page));
 }
@@ -689,7 +689,7 @@ static __always_inline bool __folio_test_movable(const struct folio *folio)
 			PAGE_MAPPING_MOVABLE;
 }
 
-static __always_inline int __PageMovable(struct page *page)
+static __always_inline int __PageMovable(const struct page *page)
 {
 	return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
 				PAGE_MAPPING_MOVABLE;
@@ -702,13 +702,13 @@ static __always_inline int __PageMovable(struct page *page)
  * is found in VM_MERGEABLE vmas.  It's a PageAnon page, pointing not to any
  * anon_vma, but to that page's node of the stable tree.
  */
-static __always_inline bool folio_test_ksm(struct folio *folio)
+static __always_inline bool folio_test_ksm(const struct folio *folio)
 {
 	return ((unsigned long)folio->mapping & PAGE_MAPPING_FLAGS) ==
 				PAGE_MAPPING_KSM;
 }
 
-static __always_inline bool PageKsm(struct page *page)
+static __always_inline bool PageKsm(const struct page *page)
 {
 	return folio_test_ksm(page_folio(page));
 }
@@ -747,9 +747,9 @@ static inline bool folio_xor_flags_has_waiters(struct folio *folio,
  * some of the bytes in it may be; see the is_partially_uptodate()
  * address_space operation.
  */
-static inline bool folio_test_uptodate(struct folio *folio)
+static inline bool folio_test_uptodate(const struct folio *folio)
 {
-	bool ret = test_bit(PG_uptodate, folio_flags(folio, 0));
+	bool ret = test_bit(PG_uptodate, const_folio_flags(folio, 0));
 	/*
 	 * Must ensure that the data we read out of the folio is loaded
 	 * _after_ we've loaded folio->flags to check the uptodate bit.
@@ -764,7 +764,7 @@ static inline bool folio_test_uptodate(struct folio *folio)
 	return ret;
 }
 
-static inline int PageUptodate(struct page *page)
+static inline int PageUptodate(const struct page *page)
 {
 	return folio_test_uptodate(page_folio(page));
 }
@@ -806,9 +806,9 @@ void set_page_writeback(struct page *page);
 #define folio_start_writeback_keepwrite(folio)	\
 	__folio_start_writeback(folio, true)
 
-static __always_inline bool folio_test_head(struct folio *folio)
+static __always_inline bool folio_test_head(const struct folio *folio)
 {
-	return test_bit(PG_head, folio_flags(folio, FOLIO_PF_ANY));
+	return test_bit(PG_head, const_folio_flags(folio, FOLIO_PF_ANY));
 }
 
 static __always_inline int PageHead(const struct page *page)
@@ -827,7 +827,7 @@ CLEARPAGEFLAG(Head, head, PF_ANY)
  *
  * Return: True if the folio is larger than one page.
  */
-static inline bool folio_test_large(struct folio *folio)
+static inline bool folio_test_large(const struct folio *folio)
 {
 	return folio_test_head(folio);
 }
@@ -856,7 +856,7 @@ TESTPAGEFLAG_FALSE(LargeRmappable, large_rmappable)
 #define PG_head_mask ((1UL << PG_head))
 
 #ifdef CONFIG_HUGETLB_PAGE
-int PageHuge(struct page *page);
+int PageHuge(const struct page *page);
 SETPAGEFLAG(HugeTLB, hugetlb, PF_SECOND)
 CLEARPAGEFLAG(HugeTLB, hugetlb, PF_SECOND)
 
@@ -869,10 +869,10 @@ CLEARPAGEFLAG(HugeTLB, hugetlb, PF_SECOND)
  * Return: True for hugetlbfs folios, false for anon folios or folios
  * belonging to other filesystems.
  */
-static inline bool folio_test_hugetlb(struct folio *folio)
+static inline bool folio_test_hugetlb(const struct folio *folio)
 {
 	return folio_test_large(folio) &&
-		test_bit(PG_hugetlb, folio_flags(folio, 1));
+		test_bit(PG_hugetlb, const_folio_flags(folio, 1));
 }
 #else
 TESTPAGEFLAG_FALSE(Huge, hugetlb)
@@ -887,7 +887,7 @@ TESTPAGEFLAG_FALSE(Huge, hugetlb)
  * hugetlbfs pages, but not normal pages. PageTransHuge() can only be
  * called only in the core VM paths where hugetlbfs pages can't exist.
  */
-static inline int PageTransHuge(struct page *page)
+static inline int PageTransHuge(const struct page *page)
 {
 	VM_BUG_ON_PAGE(PageTail(page), page);
 	return PageHead(page);
@@ -898,7 +898,7 @@ static inline int PageTransHuge(struct page *page)
  * and hugetlbfs pages, so it should only be called when it's known
  * that hugetlbfs pages aren't involved.
  */
-static inline int PageTransCompound(struct page *page)
+static inline int PageTransCompound(const struct page *page)
 {
 	return PageCompound(page);
 }
@@ -908,7 +908,7 @@ static inline int PageTransCompound(struct page *page)
  * and hugetlbfs pages, so it should only be called when it's known
  * that hugetlbfs pages aren't involved.
  */
-static inline int PageTransTail(struct page *page)
+static inline int PageTransTail(const struct page *page)
 {
 	return PageTail(page);
 }
@@ -972,7 +972,7 @@ static inline int page_type_has_type(unsigned int page_type)
 	return (int)page_type < PAGE_MAPCOUNT_RESERVE;
 }
 
-static inline int page_has_type(struct page *page)
+static inline int page_has_type(const struct page *page)
 {
 	return page_type_has_type(page->page_type);
 }
@@ -1056,7 +1056,7 @@ extern bool is_free_buddy_page(struct page *page);
 
 PAGEFLAG(Isolated, isolated, PF_ANY);
 
-static __always_inline int PageAnonExclusive(struct page *page)
+static __always_inline int PageAnonExclusive(const struct page *page)
 {
 	VM_BUG_ON_PGFLAGS(!PageAnon(page), page);
 	VM_BUG_ON_PGFLAGS(PageHuge(page) && !PageHead(page), page);
@@ -1129,12 +1129,12 @@ static __always_inline void __ClearPageAnonExclusive(struct page *page)
  * Determine if a page has private stuff, indicating that release routines
  * should be invoked upon it.
  */
-static inline int page_has_private(struct page *page)
+static inline int page_has_private(const struct page *page)
 {
 	return !!(page->flags & PAGE_FLAGS_PRIVATE);
 }
 
-static inline bool folio_has_private(struct folio *folio)
+static inline bool folio_has_private(const struct folio *folio)
 {
 	return page_has_private(&folio->page);
 }

mm/hugetlb.c

@@ -2164,9 +2164,9 @@ static bool prep_compound_gigantic_folio_for_demote(struct folio *folio,
  * transparent huge pages.  See the PageTransHuge() documentation for more
  * details.
  */
-int PageHuge(struct page *page)
+int PageHuge(const struct page *page)
 {
-	struct folio *folio;
+	const struct folio *folio;
 
 	if (!PageCompound(page))
 		return 0;