mm: use helper for calling f_op->mmap()

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
diff --git a/mm/mmap.c b/mm/mmap.c
index dc4291d..3714aa4 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1668,7 +1668,7 @@
 		 * new file must not have been exposed to user-space, yet.
 		 */
 		vma->vm_file = get_file(file);
-		error = file->f_op->mmap(file, vma);
+		error = call_mmap(file, vma);
 		if (error)
 			goto unmap_and_free_vma;