private void checkCellSizeLimit(final HRegion r, final Mutation m) throws IOException {
    if (r.maxCellSize > 0) {
      CellScanner cells = m.cellScanner();
      while (cells.advance()) {
        int size = PrivateCellUtil.estimatedSerializedSizeOf(cells.current());
        if (size > r.maxCellSize) {
          String msg = "Cell[" + cells.current() + "] with size " + size + " exceeds limit of "
            + r.maxCellSize + " bytes";
          LOG.debug(msg);
          throw new DoNotRetryIOException(msg);
        }
      }
    }
  }
Run through the regionMutation <code>rm</code> and per Mutation, do the work, and then when
done, add an instance of a {@link ResultOrException} that corresponds to each Mutation.
@param cellsToReturn Could be null. May be allocated in this method. This is what this method
                     returns as a 'result'.
@param closeCallBack the callback to be used with multigets
@param context       the current RpcCallContext
@return Return the <code>cellScanner</code> passed
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/RSRpcServices.java