public static HRegion warmupHRegion(final RegionInfo info, final TableDescriptor htd,
    final WAL wal, final Configuration conf, final RegionServerServices rsServices,
    final CancelableProgressable reporter) throws IOException {

    Objects.requireNonNull(info, "RegionInfo cannot be null");
    LOG.debug("Warmup {}", info);
    Path rootDir = CommonFSUtils.getRootDir(conf);
    Path tableDir = CommonFSUtils.getTableDir(rootDir, info.getTable());
    FileSystem fs = null;
    if (rsServices != null) {
      fs = rsServices.getFileSystem();
    }
    if (fs == null) {
      fs = rootDir.getFileSystem(conf);
    }
    HRegion r = HRegion.newHRegion(tableDir, wal, fs, conf, info, htd, null);
    r.initializeWarmup(reporter);
    r.close();
    return r;
  }
Open a Region on a read-only file-system (like hdfs snapshots)
@param conf The Configuration object to use.
@param fs   Filesystem to use
@param info Info for region to be opened.
@param htd  the table descriptor
@return new HRegion
@throws NullPointerException if {@code info} is {@code null}
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java