reiserfs: Convert release_buffer_page() to use a folio

Saves 671 bytes from an allmodconfig build (!)

Function                                     old     new   delta
release_buffer_page                         1617     946    -671
Total: Before=67656, After=66985, chg -0.99%

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>

Author: Matthew Wilcox (Oracle)

fs/reiserfs/journal.c

@@ -601,14 +601,14 @@ static int journal_list_still_alive(struct super_block *s,
  */
 static void release_buffer_page(struct buffer_head *bh)
 {
-	struct page *page = bh->b_page;
-	if (!page->mapping && trylock_page(page)) {
-		get_page(page);
+	struct folio *folio = page_folio(bh->b_page);
+	if (!folio->mapping && folio_trylock(folio)) {
+		folio_get(folio);
 		put_bh(bh);
-		if (!page->mapping)
-			try_to_free_buffers(page);
-		unlock_page(page);
-		put_page(page);
+		if (!folio->mapping)
+			try_to_free_buffers(&folio->page);
+		folio_unlock(folio);
+		folio_put(folio);
 	} else {
 		put_bh(bh);
 	}