mount: change cwd on the root before restoring mntns (v2)

We are going to make pivot_root after restoring mount name-space,
so relative paths will be used for mountpoints.

v2: print correct root in a error message
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

mount.c

@@ -1275,10 +1275,6 @@ static int cr_pivot_root(struct mount_info *mis)
 
 	pr_info("Move the root to %s\n", opts.root);
 
-	if (chdir(opts.root)) {
-		pr_perror("chdir(%s) failed", opts.root);
-		return -1;
-	}
 	if (mkdtemp(put_root) == NULL) {
 		pr_perror("Can't create a temporary directory");
 		return -1;
@@ -1472,6 +1468,11 @@ int prepare_mnt_ns(int ns_pid)
 	 * prior to recreating new ones.
 	 */
 
+	if (chdir(opts.root ? : "/")) {
+		pr_perror("chdir(%s) failed", opts.root ? : "/");
+		return -1;
+	}
+
 	if (opts.root)
 		ret = cr_pivot_root(mis);
 	else