@Override
  protected void initMapAndCache() throws IOException {
    super.initMapAndCache();
    if (myBuildKeyHashToVirtualFileMapping && myBaseStorageFile != null) {
      FileSystem projectFileFS = myBaseStorageFile.getFileSystem();
      assert !projectFileFS.isReadOnly() : "File system " + projectFileFS + " is read only";
      myKeyHashToVirtualFileMapping = new KeyHashLog<>(myKeyDescriptor, myBaseStorageFile);
    }
    else {
      myKeyHashToVirtualFileMapping = null;
    }
  }
@Override
  protected void initMapAndCache()