code: func (r *regulator) Writer(ctx context.Context, path string, append bool) (storagedriver.FileWriter, error) {
  	r.enter()
  	defer r.exit()
  
  	return r.StorageDriver.Writer(ctx, path, append)
  }
docs: // Writer stores the contents of the provided io.ReadCloser at a
  // location designated by the given path.
  // May be used to resume writing a stream by providing a nonzero offset.
  // The offset must be no larger than the CurrentSize for this path.