code: private boolean makeReadOnly(FileStatus file) throws IOException {
          if (isReadOnly(file)) {
              return false;
          }
  
          this.fileSystem.setPermission(file.getPath(), READONLY_PERMISSION);
          log.debug("MakeReadOnly '{}'.", file.getPath());
          return true;
      }
docs: Makes the file represented by the given FileStatus read-only.
  
  @param file The FileDescriptor of the file to set. If this method returns true, this FileDescriptor will
  also be updated to indicate the file is read-only.
  @return True if the file was not read-only before (and it is now), or false if the file was already read-only.
  @throws IOException If an exception occurred.