[PATCH 16/25] mm: Add folio_mapping

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

This is the folio equivalent of page_mapping().  Adjust
page_file_mapping() and page_mapping_file() to use folios internally.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/mm.h | 16 ++++++++++------
 mm/swapfile.c      |  6 +++---
 mm/util.c          | 20 ++++++++++----------
 3 files changed, 23 insertions(+), 19 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 02ccb7a09190..8bc28b4aa933 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1559,17 +1559,22 @@ void page_address_init(void);
 
 extern void *page_rmapping(struct page *page);
 extern struct anon_vma *page_anon_vma(struct page *page);
-extern struct address_space *page_mapping(struct page *page);
+struct address_space *folio_mapping(struct folio *);
+struct address_space *__folio_file_mapping(struct folio *);
 
-extern struct address_space *__page_file_mapping(struct page *);
+static inline struct address_space *page_mapping(struct page *page)
+{
+	return folio_mapping(page_folio(page));
+}
 
 static inline
 struct address_space *page_file_mapping(struct page *page)
 {
-	if (unlikely(PageSwapCache(page)))
-		return __page_file_mapping(page);
+	struct folio *folio = page_folio(page);
+	if (unlikely(FolioSwapCache(folio)))
+		return __folio_file_mapping(folio);
 
-	return page->mapping;
+	return folio->page.mapping;
 }
 
 extern pgoff_t __page_file_index(struct page *page);
@@ -1586,7 +1591,6 @@ static inline pgoff_t page_index(struct page *page)
 }
 
 bool page_mapped(struct page *page);
-struct address_space *page_mapping(struct page *page);
 struct address_space *page_mapping_file(struct page *page);
 
 /*
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 1c0a829f7311..9bf2f8daaa79 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3550,11 +3550,11 @@ struct swap_info_struct *page_swap_info(struct page *page)
 /*
  * out-of-line __page_file_ methods to avoid include hell.
  */
-struct address_space *__page_file_mapping(struct page *page)
+struct address_space *__folio_file_mapping(struct folio *folio)
 {
-	return page_swap_info(page)->swap_file->f_mapping;
+	return page_swap_info(&folio->page)->swap_file->f_mapping;
 }
-EXPORT_SYMBOL_GPL(__page_file_mapping);
+EXPORT_SYMBOL_GPL(__folio_file_mapping);
 
 pgoff_t __page_file_index(struct page *page)
 {
diff --git a/mm/util.c b/mm/util.c
index 8c9b7d1e7c49..7e9fc89c883a 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -686,39 +686,39 @@ struct anon_vma *page_anon_vma(struct page *page)
 	return __page_rmapping(page);
 }
 
-struct address_space *page_mapping(struct page *page)
+struct address_space *folio_mapping(struct folio *folio)
 {
 	struct address_space *mapping;
 
-	page = compound_head(page);
-
 	/* This happens if someone calls flush_dcache_page on slab page */
-	if (unlikely(PageSlab(page)))
+	if (unlikely(FolioSlab(folio)))
 		return NULL;
 
-	if (unlikely(PageSwapCache(page))) {
+	if (unlikely(FolioSwapCache(folio))) {
 		swp_entry_t entry;
 
-		entry.val = page_private(page);
+		entry.val = page_private(&folio->page);
 		return swap_address_space(entry);
 	}
 
-	mapping = page->mapping;
+	mapping = folio->page.mapping;
 	if ((unsigned long)mapping & PAGE_MAPPING_ANON)
 		return NULL;
 
 	return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS);
 }
-EXPORT_SYMBOL(page_mapping);
+EXPORT_SYMBOL(folio_mapping);
 
 /*
  * For file cache pages, return the address_space, otherwise return NULL
  */
 struct address_space *page_mapping_file(struct page *page)
 {
-	if (unlikely(PageSwapCache(page)))
+	struct folio *folio = page_folio(page);
+
+	if (unlikely(FolioSwapCache(folio)))
 		return NULL;
-	return page_mapping(page);
+	return folio_mapping(folio);
 }
 
 /* Slow path of page_mapcount() for compound pages */
-- 
2.29.2