private void assertSplitResultFilesCount(final FileSystem fs,
    final int expectedSplitResultFileCount, Path dir) throws IOException {
    if (expectedSplitResultFileCount != 0) {
      int resultFileCount = FSUtils.getRegionReferenceAndLinkFileCount(fs, dir);
      if (expectedSplitResultFileCount != resultFileCount) {
        throw new IOException("Failing split. Didn't have expected reference and HFileLink files"
          + ", expected=" + expectedSplitResultFileCount + ", actual=" + resultFileCount);
      }
    }
  }
Create Split directory
@param env MasterProcedureEnv
hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/SplitTableRegionProcedure.java