//
 // Corrupt specified block of file
 //
 internal virtual void CorruptBlock(Path file, ExtendedBlock blk)
 {
     // Now deliberately remove/truncate data blocks from the file.
     FilePath[] blockFiles = dfs.GetAllBlockFiles(blk);
     foreach (FilePath f in blockFiles)
     {
         f.Delete();
         Log.Info("Deleted block " + f);
     }
 }