private boolean isRegionDirPresentUnderRoot(TableName tn, String region) throws IOException {
    return this.rootFS.exists(CommonFSUtils.getRegionDir(this.rootDir, tn, region));
  }
WAL splitting implementation, splits one WAL file.
@param walStatus should be for an actual WAL file.
hbase-server/src/main/java/org/apache/hadoop/hbase/wal/WALSplitter.java