private void createStorage() throws IOException {
    File rootDirectory = new File(mBaseDirectoryPathSupplier.get(), mBaseDirectoryName);
    createRootDirectoryIfNecessary(rootDirectory);
    DiskStorage storage = new DefaultDiskStorage(rootDirectory, mVersion, mCacheErrorLogger);
    mCurrentState = new State(rootDirectory, storage);
  }
Gets a concrete disk-storage instance. If nothing has changed since the last call, then the
last state is returned

@return an instance of the appropriate DiskStorage class
@throws IOException
imagepipeline-base/src/main/java/com/facebook/cache/disk/DynamicDefaultDiskStorage.java