mm: Remove folio_test_single

There's no need for this predicate; callers can just use
!folio_test_large().
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

include/linux/page-flags.h

@@ -686,12 +686,6 @@ static inline bool test_set_page_writeback(struct page *page)
 
 __PAGEFLAG(Head, head, PF_ANY) CLEARPAGEFLAG(Head, head, PF_ANY)
 
-/* Whether there are one or multiple pages in a folio */
-static inline bool folio_test_single(struct folio *folio)
-{
-	return !folio_test_head(folio);
-}
-
 /**
  * folio_test_large() - Does this folio contain more than one page?
  * @folio: The folio to test.

mm/util.c

@@ -670,7 +670,7 @@ bool folio_mapped(struct folio *folio)
 {
 	long i, nr;
 
-	if (folio_test_single(folio))
+	if (!folio_test_large(folio))
 		return atomic_read(&folio->_mapcount) >= 0;
 	if (atomic_read(folio_mapcount_ptr(folio)) >= 0)
 		return true;