mm: reimplement folio_order() and folio_nr_pages()

Instead of calling compound_order() and compound_nr_pages(), use the folio
directly.  Saves 1905 bytes from mm/filemap.o due to folio_test_large()
now being a cheaper check than PageHead().

Link: https://lkml.kernel.org/r/20220902194653.1739778-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index e56dd8f..a37c8a2 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -729,7 +729,9 @@ static inline unsigned int compound_order(struct page *page)
  */
 static inline unsigned int folio_order(struct folio *folio)
 {
-       return compound_order(&folio->page);
+       if (!folio_test_large(folio))
+               return 0;
+       return folio->_folio_order;
 }
 
 #include <linux/huge_mm.h>
@@ -1659,7 +1661,13 @@ static inline void set_page_links(struct page *page, enum zone_type zone,
  */
 static inline long folio_nr_pages(struct folio *folio)
 {
-       return compound_nr(&folio->page);
+       if (!folio_test_large(folio))
+               return 1;
+#ifdef CONFIG_64BIT
+       return folio->_folio_nr_pages;
+#else
+       return 1L << folio->_folio_order;
+#endif
 }
 
 /**