From 8c2c4ff2f533cf37c2025655497f3dfc8cfd5eef Mon Sep 17 00:00:00 2001
From: Colin Watson <cjwatson@ubuntu.com>
Date: Fri, 4 Feb 2011 13:33:16 +0000
Subject: [PATCH] Handle empty dir passed to
 grub_find_root_device_from_mountinfo; fixes grub-mkrelpath on btrfs
 subvolumes.

---
 grub-core/kern/emu/getroot.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/grub-core/kern/emu/getroot.c b/grub-core/kern/emu/getroot.c
index 92ff971e5..c1ed35b2d 100644
--- a/grub-core/kern/emu/getroot.c
+++ b/grub-core/kern/emu/getroot.c
@@ -111,6 +111,8 @@ grub_find_root_device_from_mountinfo (const char *dir, char **relroot)
   size_t len = 0;
   char *ret = NULL;
 
+  if (! *dir)
+    dir = "/";
   if (relroot)
     *relroot = NULL;