fs: Add aops->launder_folio

Since the only difference between ->launder_page and ->launder_folio
is the type of the pointer, these can safely use a union without
affecting bisectability.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Acked-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Tested-by: Mike Marshall <hubcap@omnibond.com> # orangefs
Tested-by: David Howells <dhowells@redhat.com> # afs

Documentation/filesystems/locking.rst

@@ -257,7 +257,7 @@ prototypes::
 	bool (*isolate_page) (struct page *, isolate_mode_t);
 	int (*migratepage)(struct address_space *, struct page *, struct page *);
 	void (*putback_page) (struct page *);
-	int (*launder_page)(struct page *);
+	int (*launder_folio)(struct folio *);
 	bool (*is_partially_uptodate)(struct folio *, size_t from, size_t count);
 	int (*error_remove_page)(struct address_space *, struct page *);
 	int (*swap_activate)(struct file *);
@@ -285,7 +285,7 @@ direct_IO:
 isolate_page:		yes
 migratepage:		yes (both)
 putback_page:		yes
-launder_page:		yes
+launder_folio:		yes
 is_partially_uptodate:	yes
 error_remove_page:	yes
 swap_activate:		no
@@ -385,9 +385,9 @@ the kernel assumes that the fs has no private interest in the buffers.
 ->freepage() is called when the kernel is done dropping the page
 from the page cache.
 
-->launder_page() may be called prior to releasing a page if
-it is still found to be dirty. It returns zero if the page was successfully
-cleaned, or an error value if not. Note that in order to prevent the page
+->launder_folio() may be called prior to releasing a folio if
+it is still found to be dirty. It returns zero if the folio was successfully
+cleaned, or an error value if not. Note that in order to prevent the folio
 getting mapped back in and redirtied, it needs to be kept locked
 across the entire operation.
 

Documentation/filesystems/vfs.rst

@@ -745,7 +745,7 @@ cache in your filesystem.  The following members are defined:
 		int (*migratepage) (struct page *, struct page *);
 		/* put migration-failed page back to right list */
 		void (*putback_page) (struct page *);
-		int (*launder_page) (struct page *);
+		int (*launder_folio) (struct folio *);
 
 		bool (*is_partially_uptodate) (struct folio *, size_t from,
 					       size_t count);
@@ -930,9 +930,9 @@ cache in your filesystem.  The following members are defined:
 ``putback_page``
 	Called by the VM when isolated page's migration fails.
 
-``launder_page``
-	Called before freeing a page - it writes back the dirty page.
-	To prevent redirtying the page, it is kept locked during the
+``launder_folio``
+	Called before freeing a folio - it writes back the dirty folio.
+	To prevent redirtying the folio, it is kept locked during the
 	whole operation.
 
 ``is_partially_uptodate``

include/linux/fs.h

@@ -399,7 +399,10 @@ struct address_space_operations {
 			struct page *, struct page *, enum migrate_mode);
 	bool (*isolate_page)(struct page *, isolate_mode_t);
 	void (*putback_page)(struct page *);
-	int (*launder_page) (struct page *);
+	union {
+		int (*launder_page) (struct page *);
+		int (*launder_folio) (struct folio *);
+	};
 	bool (*is_partially_uptodate) (struct folio *, size_t from,
 			size_t count);
 	void (*is_dirty_writeback) (struct page *, bool *, bool *);

mm/truncate.c

@@ -614,13 +614,13 @@ failed:
 	return 0;
 }
 
-static int do_launder_folio(struct address_space *mapping, struct folio *folio)
+static int folio_launder(struct address_space *mapping, struct folio *folio)
 {
 	if (!folio_test_dirty(folio))
 		return 0;
-	if (folio->mapping != mapping || mapping->a_ops->launder_page == NULL)
+	if (folio->mapping != mapping || mapping->a_ops->launder_folio == NULL)
 		return 0;
-	return mapping->a_ops->launder_page(&folio->page);
+	return mapping->a_ops->launder_folio(folio);
 }
 
 /**
@@ -686,7 +686,7 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 				unmap_mapping_folio(folio);
 			BUG_ON(folio_mapped(folio));
 
-			ret2 = do_launder_folio(mapping, folio);
+			ret2 = folio_launder(mapping, folio);
 			if (ret2 == 0) {
 				if (!invalidate_complete_folio2(mapping, folio))
 					ret2 = -EBUSY;