mm: Make some folio function arguments const

Mark the folio* argument to some of the folio accessor functions as a const
pointer.

Signed-off-by: David Howells <dhowells@redhat.com>

include/linux/mm.h

@@ -676,7 +676,7 @@ int vma_is_stack_for_current(struct vm_area_struct *vma);
 struct mmu_gather;
 struct inode;
 
-static inline unsigned int compound_order(struct page *page)
+static inline unsigned int compound_order(const struct page *page)
 {
 	if (!PageHead(page))
 		return 0;
@@ -692,7 +692,7 @@ static inline unsigned int compound_order(struct page *page)
  *
  * Return: The order of the folio.
  */
-static inline unsigned int folio_order(struct folio *folio)
+static inline unsigned int folio_order(const struct folio *folio)
 {
 	return compound_order(&folio->page);
 }
@@ -912,7 +912,7 @@ static inline void set_compound_order(struct page *page, unsigned int order)
 }
 
 /* Returns the number of pages in this potentially compound page. */
-static inline unsigned long compound_nr(struct page *page)
+static inline unsigned long compound_nr(const struct page *page)
 {
 	if (!PageHead(page))
 		return 1;
@@ -1516,7 +1516,7 @@ static inline unsigned long page_to_section(const struct page *page)
  *
  * Return: The Page Frame Number of the first page in the folio.
  */
-static inline unsigned long folio_pfn(struct folio *folio)
+static inline unsigned long folio_pfn(const struct folio *folio)
 {
 	return page_to_pfn(&folio->page);
 }
@@ -1592,7 +1592,7 @@ static inline bool page_needs_cow_for_dma(struct vm_area_struct *vma,
 
 /* MIGRATE_CMA and ZONE_MOVABLE do not allow pin pages */
 #ifdef CONFIG_MIGRATION
-static inline bool is_pinnable_page(struct page *page)
+static inline bool is_pinnable_page(const struct page *page)
 {
 #ifdef CONFIG_CMA
 	int mt = get_pageblock_migratetype(page);
@@ -1603,13 +1603,13 @@ static inline bool is_pinnable_page(struct page *page)
 	return !(is_zone_movable_page(page) || is_zero_pfn(page_to_pfn(page)));
 }
 #else
-static inline bool is_pinnable_page(struct page *page)
+static inline bool is_pinnable_page(const struct page *page)
 {
 	return true;
 }
 #endif
 
-static inline bool folio_is_pinnable(struct folio *folio)
+static inline bool folio_is_pinnable(const struct folio *folio)
 {
 	return is_pinnable_page(&folio->page);
 }
@@ -1642,7 +1642,7 @@ static inline void set_page_links(struct page *page, enum zone_type zone,
  *
  * Return: A positive power of two.
  */
-static inline long folio_nr_pages(struct folio *folio)
+static inline long folio_nr_pages(const struct folio *folio)
 {
 	return compound_nr(&folio->page);
 }
@@ -1678,7 +1678,7 @@ static inline struct folio *folio_next(struct folio *folio)
  * it from being split.  It is not necessary for the folio to be locked.
  * Return: The base-2 logarithm of the size of this folio.
  */
-static inline unsigned int folio_shift(struct folio *folio)
+static inline unsigned int folio_shift(const struct folio *folio)
 {
 	return PAGE_SHIFT + folio_order(folio);
 }
@@ -1691,7 +1691,7 @@ static inline unsigned int folio_shift(struct folio *folio)
  * it from being split.  It is not necessary for the folio to be locked.
  * Return: The number of bytes in this folio.
  */
-static inline size_t folio_size(struct folio *folio)
+static inline size_t folio_size(const struct folio *folio)
 {
 	return PAGE_SIZE << folio_order(folio);
 }

include/linux/page-flags.h

@@ -262,7 +262,7 @@ static inline bool hugetlb_optimize_vmemmap_enabled(void)
 }
 #endif
 
-static __always_inline int page_is_fake_head(struct page *page)
+static __always_inline int page_is_fake_head(const struct page *page)
 {
 	return page_fixed_fake_head(page) != page;
 }
@@ -783,7 +783,7 @@ static __always_inline bool folio_test_head(struct folio *folio)
 	return test_bit(PG_head, folio_flags(folio, FOLIO_PF_ANY));
 }
 
-static __always_inline int PageHead(struct page *page)
+static __always_inline int PageHead(const struct page *page)
 {
 	PF_POISONED_CHECK(page);
 	return test_bit(PG_head, &page->flags) && !page_is_fake_head(page);