[jira] [Created] (HDFS-6423) Diskspace quota usage is wrongly updated when appending data from partial block

["Jing Zhao (JIRA)" <ji...@apache.org>]

Jing Zhao created HDFS-6423:
-------------------------------

             Summary: Diskspace quota usage is wrongly updated when appending data from partial block
                 Key: HDFS-6423
                 URL: https://issues.apache.org/jira/browse/HDFS-6423
             Project: Hadoop HDFS
          Issue Type: Bug
            Reporter: Jing Zhao
            Assignee: Jing Zhao


When appending new data to a file whose last block is a partial block, the diskspace quota usage is not correctly update. For example, suppose the block size is 1024 bytes, and a file has size 1536 bytes (1.5 blocks). If we then append another 1024 bytes to the file, the diskspace usage for this file will not be updated to (2560 * replication) as expected, but (2048 * replication).

The cause of the issue is that in FSNamesystem#commitOrCompleteLastBlock, we have 
{code}
    // Adjust disk space consumption if required
    final long diff = fileINode.getPreferredBlockSize() - commitBlock.getNumBytes();    
    if (diff > 0) {
      try {
        String path = fileINode.getFullPathName();
        dir.updateSpaceConsumed(path, 0, -diff*fileINode.getFileReplication());
      } catch (IOException e) {
        LOG.warn("Unexpected exception while updating disk space.", e);
      }
    }
{code}
This code assumes that the last block of the file has never been completed before, thus is always counted with the preferred block size in quota computation.




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