@Override
    public void setReadahead(Long readahead) throws IOException, UnsupportedOperationException {
      in.setReadahead(readahead);
    }
Try to open the file from one of the available locations.
@return FSDataInputStream stream of the opened file link
@throws IOException on unexpected error, or file not found.
hbase-server/src/main/java/org/apache/hadoop/hbase/io/FileLink.java