[PATCH] handle setup_swap_extents() error in swapon.

From: Hugh Dickins <hugh@veritas.com>

It's good that swapon fails on a tmpfs file ("swapfile has holes"), but not
good that it then hangs up: note error from setup_swap_extents.

mm/swapfile.c

@@ -1403,7 +1403,8 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
 	p->max = maxpages;
 	p->pages = nr_good_pages;
 
-	if (setup_swap_extents(p))
+	error = setup_swap_extents(p);
+	if (error)
 		goto bad_swap;
 
 	swap_list_lock();