udf: Try harder when looking for VAT inode

Some disks do not contain VAT inode in the last recorded block as required
by the standard but a few blocks earlier (or the number of recorded blocks
is wrong). So look for the VAT inode a bit before the end of the media.

Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 24 insertions, 8 deletions

diff --git a/fs/udf/super.c b/fs/udf/super.c
index 9d1b8c2e6c45..1e4543cbcd27 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -1078,21 +1078,39 @@ static int udf_fill_partdesc_info(struct super_block *sb,
         return 0;
 }
 
-static int udf_load_vat(struct super_block *sb, int p_index, int type1_index)
+static void udf_find_vat_block(struct super_block *sb, int p_index,
+                               int type1_index, sector_t start_block)
 {
         struct udf_sb_info *sbi = UDF_SB(sb);
         struct udf_part_map *map = &sbi->s_partmaps[p_index];
+        sector_t vat_block;
         struct kernel_lb_addr ino;
+
+        /*
+         * VAT file entry is in the last recorded block. Some broken disks have
+         * it a few blocks before so try a bit harder...
+         */
+        ino.partitionReferenceNum = type1_index;
+        for (vat_block = start_block;
+             vat_block >= map->s_partition_root &&
+             vat_block >= start_block - 3 &&
+             !sbi->s_vat_inode; vat_block--) {
+                ino.logicalBlockNum = vat_block - map->s_partition_root;
+                sbi->s_vat_inode = udf_iget(sb, &ino);
+        }
+}
+
+static int udf_load_vat(struct super_block *sb, int p_index, int type1_index)
+{
+        struct udf_sb_info *sbi = UDF_SB(sb);
+        struct udf_part_map *map = &sbi->s_partmaps[p_index];
         struct buffer_head *bh = NULL;
         struct udf_inode_info *vati;
         uint32_t pos;
         struct virtualAllocationTable20 *vat20;
         sector_t blocks = sb->s_bdev->bd_inode->i_size >> sb->s_blocksize_bits;
 
-        /* VAT file entry is in the last recorded block */
-        ino.partitionReferenceNum = type1_index;
-        ino.logicalBlockNum = sbi->s_last_block - map->s_partition_root;
-        sbi->s_vat_inode = udf_iget(sb, &ino);
+        udf_find_vat_block(sb, p_index, type1_index, sbi->s_last_block);
         if (!sbi->s_vat_inode &&
             sbi->s_last_block != blocks - 1) {
                 printk(KERN_NOTICE "UDF-fs: Failed to read VAT inode from the"
@@ -1100,9 +1118,7 @@ static int udf_load_vat(struct super_block *sb, int p_index, int type1_index)
                        "block of the device (%lu).\n",
                        (unsigned long)sbi->s_last_block,
                        (unsigned long)blocks - 1);
-                ino.partitionReferenceNum = type1_index;
-                ino.logicalBlockNum = blocks - 1 - map->s_partition_root;
-                sbi->s_vat_inode = udf_iget(sb, &ino);
+                udf_find_vat_block(sb, p_index, type1_index, blocks - 1);
         }
         if (!sbi->s_vat_inode)
                 return 1;