ext4: calculate and verify block bitmap checksum

Compute and verify the checksum of the block bitmap; this checksum is
stored in the block group descriptor.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/resize.c

@@ -1107,6 +1107,13 @@ static int ext4_set_bitmap_checksums(struct super_block *sb,
 				   EXT4_INODES_PER_GROUP(sb) / 8);
 	brelse(bh);
 
+	bh = ext4_get_bitmap(sb, group_data->block_bitmap);
+	if (!bh)
+		return -EIO;
+	ext4_block_bitmap_csum_set(sb, group, gdp, bh,
+				   EXT4_BLOCKS_PER_GROUP(sb) / 8);
+	brelse(bh);
+
 	return 0;
 }