private static List<Path> getFilePaths(final FileSystem fs, final Path dir,
    final PathFilter pathFilter) throws IOException {
    FileStatus[] fds = fs.listStatus(dir, pathFilter);
    List<Path> files = new ArrayList<>(fds.length);
    for (FileStatus fdfs : fds) {
      Path fdPath = fdfs.getPath();
      files.add(fdPath);
    }
    return files;
  }
Given a particular region dir, return all the familydirs inside it
@param fs        A file system for the Path
@param regionDir Path to a specific region directory
@return List of paths to valid family directories in region dir.
hbase-server/src/main/java/org/apache/hadoop/hbase/util/FSUtils.java