[PATCH] use UUID to map system devices to grub devices

[Felix Zielcke <fzielcke@z-51.de>]

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As requested by Robert on IRC, this is a split from my dmraid patch.
On dmraid devices HDIO_GETGEO returns 0 for all fields, so the current
way of grub_util_biosdisk_get_grub_dev just can't work.
So I use blkid to get the UUID of the device and then a new nested
function to find out the grub device like search does.

I think this is with intent from the kernel that it just returns 0's.
Maybe it just can't distinguish between a device mapper setup which goes
over multiple partitions or harddisks of different size not from one
which goes only over complete harddisks with same size like in dmraid
Hm but even if, I think it wouldn't help in case of RAID != 1. Sector
count could be > then last sector of one disk or not?

-- 
Felix Zielcke
Proud Debian Maintainer

[-- Attachment #2: find_by_uuid.patch --]
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2009-07-26  Felix Zielcke  <fzielcke@z-51.de>

	* util/hostdisk.c: Include <grub/file.h>.
	(grub_util_biosdisk_get_grub_dev): Use new nested function
	find_partition_by_uuid in the case that the HD_GETGEO ioctl
	returns 0 for the sectors count, to get the value of dos_part.

diff --git a/util/hostdisk.c b/util/hostdisk.c
index 5842698..843bfb4 100644
--- a/util/hostdisk.c
+++ b/util/hostdisk.c
@@ -25,6 +25,7 @@
 #include <grub/util/misc.h>
 #include <grub/util/hostdisk.h>
 #include <grub/misc.h>
+#include <grub/file.h>
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -925,7 +926,7 @@ grub_util_biosdisk_get_grub_dev (const char *os_dev)
      does not count the extended partition and missing primary
      partitions.  Use same method as on Linux here.  */
   {
-    char *name;
+    char *name, *os_dev_uuid;
     grub_disk_t disk;
     int fd;
     struct hd_geometry hdg;
@@ -975,7 +976,46 @@ grub_util_biosdisk_get_grub_dev (const char *os_dev)
 
 	return 0;
       }
+    auto int find_partition_by_uuid (const char *name);
 
+    int find_partition_by_uuid (const char *name)
+    {
+      grub_device_t dev;
+
+      if (name[0] == 'f' && name[1] == 'd'
+	  && name[2] >= '0' && name[2] <= '9')
+	return 0;
+
+      dev = grub_device_open (name);
+      if (dev)
+	{
+	  grub_fs_t fs;
+
+	  fs = grub_fs_probe (dev);
+
+	  if (fs && fs->uuid)
+	    {
+	      char *uuid, *p;
+
+	      (fs->uuid) (dev, &uuid);
+	      if (grub_errno == GRUB_ERR_NONE && uuid)
+		{
+		  if (grub_strcasecmp (uuid, os_dev_uuid) == 0)
+		    {
+		      p = strchr (name, ',');
+		      dos_part = atoi (p);
+		      if (strchr (p, ','))
+			grub_util_error ("BSD partitions not yet supported");
+		      free (uuid);
+		      return 1;
+		    }
+		  free (uuid);
+		}
+	    }
+	  grub_device_close (dev);
+	}
+      return 0;
+    }
     name = make_device_name (drive, -1, -1);
 
     if (MAJOR (st.st_rdev) == FLOPPY_MAJOR)
@@ -1005,28 +1045,61 @@ grub_util_biosdisk_get_grub_dev (const char *os_dev)
     if (hdg.start == 0 && device_is_wholedisk (os_dev))
       return name;
 
-    grub_util_info ("opening the device %s", name);
-    disk = grub_disk_open (name);
-    free (name);
-
-    if (! disk)
-      return 0;
 
-    grub_partition_iterate (disk, find_partition);
-    if (grub_errno != GRUB_ERR_NONE)
+    if (hdg.sectors == 0)
       {
-	grub_disk_close (disk);
-	return 0;
+	FILE *fp;
+	char *free_ptr, *p, *q;
+	int len = 512;
+
+	p = xmalloc (strlen (os_dev) + strlen ("blkid ") + 1);
+	strcpy (p, "blkid ");
+	strcat (p, os_dev);
+	fp = popen (p, "r");
+	free (p);
+	do {
+	  p = xmalloc (len);
+	  p = fgets (p, len, fp);
+	  if (! p)
+	    return 0;
+	  len *= 2;
+	} while (! strchr (p, '\n'));
+	free_ptr = p;
+	p = strstr (p , "UUID=");
+	if (! p)
+	  return 0;
+	p += strlen ("UUID=\"");
+	q = strchr (p, '\"');
+	if (q)
+	  *q = '\0';
+	os_dev_uuid = p;
+	pclose (fp);
+	grub_device_iterate (find_partition_by_uuid);
+	free (free_ptr);
       }
+    else
+      {
+	grub_util_info ("opening the device %s", name);
+	disk = grub_disk_open (name);
+	free (name);
 
+	if (! disk)
+	  return 0;
+	grub_partition_iterate (disk, find_partition);
+	if (grub_errno != GRUB_ERR_NONE)
+	  {
+	    grub_disk_close (disk);
+	    return 0;
+	  }
+	if (dos_part < 0)
+	  grub_disk_close (disk);
+      }
     if (dos_part < 0)
       {
-	grub_disk_close (disk);
 	grub_error (GRUB_ERR_BAD_DEVICE,
 		    "cannot find the partition of `%s'", os_dev);
 	return 0;
       }
-
     return make_device_name (drive, dos_part, bsd_part);
   }