Upstream-Status: Backport

Patch is a slightly edited version from debian. Upstream link is:
http://bzr.savannah.gnu.org/lh/grub/trunk/grub/revision/3318

Description: Don't stat devices unless we have to
Author: Vladimir Serbinenko <phcoder@gmail.com>
Author: Colin Watson <cjwatson@ubuntu.com>
Bug-Debian: http://bugs.debian.org/627587
Forwarded: yes
Applied-Upstream: http://bazaar.launchpad.net/~vcs-imports/grub/grub2-bzr/revision/3318
Last-Update: 2011-05-31

Index: b/grub-core/kern/emu/getroot.c
===================================================================
--- a/grub-core/kern/emu/getroot.c
+++ b/grub-core/kern/emu/getroot.c
@@ -358,7 +358,7 @@
 
       if (S_ISLNK (st.st_mode)) {
 #ifdef __linux__
-	if (strcmp (dir, "mapper") == 0) {
+	if (strcmp (dir, "mapper") == 0 || strcmp (dir, "/dev/mapper") == 0) {
 	  /* Follow symbolic links under /dev/mapper/; the canonical name
 	     may be something like /dev/dm-0, but the names under
 	     /dev/mapper/ are more human-readable and so we prefer them if
@@ -609,20 +609,27 @@
 
   if (os_dev)
     {
-      if (stat (os_dev, &st) >= 0)
-	dev = st.st_rdev;
-      else
-	grub_util_error ("cannot stat `%s'", os_dev);
-      free (os_dev);
+      char *tmp = os_dev;
+      os_dev = canonicalize_file_name (os_dev);
+      free (tmp);
     }
-  else
+
+  if (os_dev)
     {
-      if (stat (dir, &st) >= 0)
-	dev = st.st_dev;
-      else
-	grub_util_error ("cannot stat `%s'", dir);
+      if (strncmp (os_dev, "/dev/dm-", sizeof ("/dev/dm-") - 1) != 0)
+	return os_dev;
+      if (stat (os_dev, &st) < 0)
+	grub_util_error ("cannot stat `%s'", os_dev);
+      free (os_dev);
+      dev = st.st_rdev;
+      return grub_find_device ("/dev/mapper", dev);
     }
 
+  if (stat (dir, &st) < 0)
+    grub_util_error ("cannot stat `%s'", dir);
+
+  dev = st.st_dev;
+  
 #ifdef __CYGWIN__
   /* Cygwin specific function.  */
   os_dev = grub_find_device (dir, dev);