code: void stopDecommission(DatanodeDescriptor node)
      throws IOException {
      if ((node.isDecommissionInProgress() &&
        ((Monitor) dnthread.getRunnable()).stopDecommission(node)) ||
        node.isDecommissioned()) {
        LOG.info("Stop Decommissioning node " + node.getName());
        synchronized (heartbeats) {
          updateStats(node, false);
          node.stopDecommission();
          updateStats(node, true);
        }
  
        // Make sure we process over replicated blocks.
        writeLock();
        try {
          Iterator<BlockInfo> it = node.getBlockIterator();
          while (it.hasNext()) {
            Block b = it.next();
            if (countLiveNodes(b) > getReplication(b)) {
              overReplicatedBlocks.add(b);
            }
          }
        } finally {
          writeUnlock();
        }
      }
    }
docs: Stop decommissioning the specified datanodes.