HDFS-15798. EC: Reconstruct task failed, and It would be XmitsInProgress of DN has negative number. Contributed by huhaiyang

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/erasurecode/ErasureCodingWorker.java

@@ -121,7 +121,6 @@ public final class ErasureCodingWorker {
   public void processErasureCodingTasks(
       Collection<BlockECReconstructionInfo> ecTasks) {
     for (BlockECReconstructionInfo reconInfo : ecTasks) {
-      int xmitsSubmitted = 0;
       try {
         StripedReconstructionInfo stripedReconInfo =
             new StripedReconstructionInfo(
@@ -134,20 +133,19 @@ public final class ErasureCodingWorker {
         final StripedBlockReconstructor task =
             new StripedBlockReconstructor(this, stripedReconInfo);
         if (task.hasValidTargets()) {
+          stripedReconstructionPool.submit(task);
           // See HDFS-12044. We increase xmitsInProgress even the task is only
           // enqueued, so that
           //   1) NN will not send more tasks than what DN can execute and
           //   2) DN will not throw away reconstruction tasks, and instead keeps
           //      an unbounded number of tasks in the executor's task queue.
-          xmitsSubmitted = Math.max((int)(task.getXmits() * xmitWeight), 1);
+          int xmitsSubmitted = Math.max((int)(task.getXmits() * xmitWeight), 1);
           getDatanode().incrementXmitsInProcess(xmitsSubmitted);
-          stripedReconstructionPool.submit(task);
         } else {
           LOG.warn("No missing internal block. Skip reconstruction for task:{}",
               reconInfo);
         }
       } catch (Throwable e) {
-        getDatanode().decrementXmitsInProgress(xmitsSubmitted);
         LOG.warn("Failed to reconstruct striped block {}",
             reconInfo.getExtendedBlock().getLocalBlock(), e);
       }