[PATCH] mm: optimise page_count

Optimise page_count compound page test and make it consistent with similar
functions.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7d8c127..6aa016f 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -311,7 +311,7 @@
 
 static inline int page_count(struct page *page)
 {
-	if (PageCompound(page))
+	if (unlikely(PageCompound(page)))
 		page = (struct page *)page_private(page);
 	return atomic_read(&page->_count);
 }