/**
   * Check whether the rolling upgrade marker file exists for each BP storage
   * root. If it does exist, then the marker file is cleared and more
   * importantly the layout upgrade is finalized.
   */
/**
   * Check whether the rolling upgrade marker file exists for each BP storage
   * root. If it does exist, then the marker file is cleared and more
   * importantly the layout upgrade is finalized.
   */ | BlockPoolSliceStorage.java