[jira] [Created] (HDFS-16933) A race in SerialNumberMap will cause wrong ownership

["ZanderXu (Jira)" <ji...@apache.org>]

ZanderXu created HDFS-16933:
-------------------------------

             Summary: A race in SerialNumberMap will cause wrong ownership
                 Key: HDFS-16933
                 URL: https://issues.apache.org/jira/browse/HDFS-16933
             Project: Hadoop HDFS
          Issue Type: Bug
            Reporter: ZanderXu
            Assignee: ZanderXu


If namenode enables parallel fsimage loading, a race that occurs in SerialNumberMap will cause wrong owner ship for INodes.
{code:java}
public int get(T t) {
  if (t == null) {
    return 0;
  }
  Integer sn = t2i.get(t);
  if (sn == null) {
    // Assume there are two thread with different t, such as:
    // T1 with hbase
    // T2 with hdfs
    // If T1 and T2 get the sn in the same time, they will get the same sn, such as 10
    sn = current.getAndIncrement();
    if (sn > max) {
      current.getAndDecrement();
      throw new IllegalStateException(name + ": serial number map is full");
    }
    Integer old = t2i.putIfAbsent(t, sn);
    if (old != null) {
      current.getAndDecrement();
      return old;
    }
    // If T1 puts the 10->hbase to the i2t first, T2 will use 10 -> hdfs to overwrite it. So it will cause that the Inodes will get a wrong owner hdfs, actual it should be hbase.
    i2t.put(sn, t);
  }
  return sn;
} {code}



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