Make reiserfs label retrieval similar to other *_label functions.

* grub-core/fs/reiserfs.c (grub_reiserfs_superblock): New field label.
	(REISERFS_MAX_LABEL_LENGTH): Removed.
	(REISERFS_LABEL_OFFSET): Likewise.
	(grub_reiserfs_label): Rewritten.

grub-core/fs/reiserfs.c

@@ -57,8 +57,6 @@ GRUB_MOD_LICENSE ("GPLv3+");
 #define REISERFS_MAGIC_DESC_BLOCK "ReIsErLB"
 /* If the 3rd bit of an item state is set, then it's visible.  */
 #define GRUB_REISERFS_VISIBLE_MASK ((grub_uint16_t) 0x04)
-#define REISERFS_MAX_LABEL_LENGTH 16
-#define REISERFS_LABEL_OFFSET 0x64
 
 #define S_IFLNK 0xA000
 
@@ -109,6 +107,7 @@ struct grub_reiserfs_superblock
   grub_uint32_t inode_generation;
   grub_uint8_t unused[4];
   grub_uint16_t uuid[8];
+  char label[16];
 } __attribute__ ((packed));
 
 struct grub_reiserfs_journal_header
@@ -1323,14 +1322,24 @@ grub_reiserfs_dir (grub_device_t device, const char *path,
 static grub_err_t
 grub_reiserfs_label (grub_device_t device, char **label)
 {
-  *label = grub_malloc (REISERFS_MAX_LABEL_LENGTH);
-  if (*label)
+  struct grub_reiserfs_data *data;
+  grub_disk_t disk = device->disk;
+
+  grub_dl_ref (my_mod);
+
+  data = grub_reiserfs_mount (disk);
+  if (data)
     {
-      grub_disk_read (device->disk,
-                      REISERFS_SUPER_BLOCK_OFFSET / GRUB_DISK_SECTOR_SIZE,
-                      REISERFS_LABEL_OFFSET, REISERFS_MAX_LABEL_LENGTH,
-                      *label);
+      *label = grub_strndup (data->superblock.label,
+			     sizeof (data->superblock.label));
     }
+  else
+    *label = NULL;
+
+  grub_dl_unref (my_mod);
+
+  grub_free (data);
+
   return grub_errno;
 }