iomap: Convert iomap_migrate_page to use folios

The arguments are still pages for now, but we can use folios internally
and cut out a lot of calls to compound_head().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

fs/iomap/buffered-io.c

@@ -492,19 +492,21 @@ int
 iomap_migrate_page(struct address_space *mapping, struct page *newpage,
 		struct page *page, enum migrate_mode mode)
 {
+	struct folio *folio = page_folio(page);
+	struct folio *newfolio = page_folio(newpage);
 	int ret;
 
-	ret = migrate_page_move_mapping(mapping, newpage, page, 0);
+	ret = folio_migrate_mapping(mapping, newfolio, folio, 0);
 	if (ret != MIGRATEPAGE_SUCCESS)
 		return ret;
 
-	if (page_has_private(page))
-		attach_page_private(newpage, detach_page_private(page));
+	if (folio_test_private(folio))
+		folio_attach_private(newfolio, folio_detach_private(folio));
 
 	if (mode != MIGRATE_SYNC_NO_COPY)
-		migrate_page_copy(newpage, page);
+		folio_migrate_copy(newfolio, folio);
 	else
-		migrate_page_states(newpage, page);
+		folio_migrate_flags(newfolio, folio);
 	return MIGRATEPAGE_SUCCESS;
 }
 EXPORT_SYMBOL_GPL(iomap_migrate_page);