Index: sys/fs/nullfs/null_vnops.c
===================================================================
--- sys/fs/nullfs/null_vnops.c	(revision 254941)
+++ sys/fs/nullfs/null_vnops.c	(working copy)
@@ -858,6 +858,15 @@
 	return (error);
 }
 
+static int
+null_link(struct vop_link_args *ap)
+{
+
+	if (ap->a_tdvp->v_mount != ap->a_vp->v_mount)
+		return (EXDEV);
+	return (null_bypass((struct vop_generic_args *)ap));
+}
+
 /*
  * Global vfs data structures
  */
@@ -871,6 +880,7 @@
 	.vop_getwritemount =	null_getwritemount,
 	.vop_inactive =		null_inactive,
 	.vop_islocked =		vop_stdislocked,
+	.vop_link =		null_link,
 	.vop_lock1 =		null_lock,
 	.vop_lookup =		null_lookup,
 	.vop_open =		null_open,