Avoid the GEOM topology lock recursion when we automatically expand a…

… pool.

The steps to reproduce the problem:

	mdconfig -a -t swap -s 3g -u 0
	gpart create -s GPT md0
	gpart add -t freebsd-zfs -s 1g md0
	zpool create -o autoexpand=on foo md0p1
	gpart resize -i 1 -s 2g md0

sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c

@@ -973,18 +973,22 @@ static void
 vdev_geom_close(vdev_t *vd)
 {
 	struct g_consumer *cp;
+	int locked;
 
 	cp = vd->vdev_tsd;
 
 	DROP_GIANT();
-	g_topology_lock();
+	locked = g_topology_locked();
+	if (!locked)
+		g_topology_lock();
 
 	if (!vd->vdev_reopening ||
 	    (cp != NULL && ((cp->flags & G_CF_ORPHAN) != 0 ||
 	    (cp->provider != NULL && cp->provider->error != 0))))
 		vdev_geom_close_locked(vd);
 
-	g_topology_unlock();
+	if (!locked)
+		g_topology_unlock();
 	PICKUP_GIANT();
 }