long computeSize(Region r) {
    long regionSize = 0L;
    for (Store store : r.getStores()) {
      regionSize += store.getHFilesSize();
    }
    if (LOG.isTraceEnabled()) {
      LOG.trace("Size of " + r + " is " + regionSize);
    }
    return regionSize;
  }
Computes total FileSystem size for the given {@link Region}.
@param r The region
@return The size, in bytes, of the Region.
hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/FileSystemUtilizationChore.java