public void initReader() throws IOException {
    if (initialReader == null) {
      synchronized (this) {
        if (initialReader == null) {
          try {
            open();
          } catch (Exception e) {
            try {
              boolean evictOnClose = cacheConf != null ? cacheConf.shouldEvictOnClose() : true;
              this.closeStoreFile(evictOnClose);
            } catch (IOException ee) {
              LOG.warn("failed to close reader", ee);
            }
            throw e;
          }
        }
      }
    }
  }
Initialize the reader used for pread.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HStoreFile.java