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https://issues.apache.org/jira/browse/HDFS-6423?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14004423#comment-14004423
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Jing Zhao commented on HDFS-6423:
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Thanks for the comments, Nicholas!
The issue here is that in commitOrCompleteLastBlock, when we find that the old
length of the block is >0, it is hard to determine whether the block length is
derived from an fsync call or a previous close call. The unit test
testUpdateQuotaForFSync is for this scenario. Thus in the current patch I just
update the quota based on the length reported in the fsync.
> Diskspace quota usage is wrongly updated when appending data to 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
> Attachments: HDFS-6423.000.patch, HDFS-6423.001.patch
>
>
> 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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