mm: document PageHuge somewhat

Acked-by: NDavid Rientjes <rientjes@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/hugetlb.c

@@ -671,6 +671,11 @@ static void prep_compound_gigantic_page(struct page *page, unsigned long order)
 	}
 }
 
+/*
+ * PageHuge() only returns true for hugetlbfs pages, but not for normal or
+ * transparent huge pages.  See the PageTransHuge() documentation for more
+ * details.
+ */
 int PageHuge(struct page *page)
 {
 	compound_page_dtor *dtor;