udf: Fix loading of VAT inode when drive wrongly reports number of recorded blocks

VAT inode is located in the last block recorded block of the medium. When the
drive errorneously reports number of recorded blocks, we failed to load the VAT
inode and thus mount the medium. This patch makes kernel try to read VAT inode
from the last block of the device if it is different from the last recorded
block.
Signed-off-by: Jan Kara <jack@suse.cz>

fs/udf/super.c

@@ -1087,11 +1087,23 @@ static int udf_load_vat(struct super_block *sb, int p_index, int type1_index)
 	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);
+	if (!sbi->s_vat_inode &&
+	    sbi->s_last_block != blocks - 1) {
+		printk(KERN_NOTICE "UDF-fs: Failed to read VAT inode from the"
+		       " last recorded block (%lu), retrying with the last "
+		       "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);
+	}
 	if (!sbi->s_vat_inode)
 		return 1;