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https://issues.apache.org/jira/browse/HDFS-10797?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15536805#comment-15536805
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Sean Mackrory commented on HDFS-10797:
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findbugs output is correct: I'm using synchronization to prevent any problems
caused by the fact that we swap the counts object to tally up deleted,
snapshotted space. We did this before, and it *should* be fine, since this is
single-threaded everywhere I've seen, but thought it'd be wise to guard just in
case. I'll synchronize the entire function on the context object instead and
resubmit - other feedback welcome in the mean time, since that won't affect
most of the patch.
> Disk usage summary of snapshots causes renamed blocks to get counted twice
> --------------------------------------------------------------------------
>
> Key: HDFS-10797
> URL: https://issues.apache.org/jira/browse/HDFS-10797
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Sean Mackrory
> Assignee: Sean Mackrory
> Attachments: HDFS-10797.001.patch, HDFS-10797.002.patch,
> HDFS-10797.003.patch, HDFS-10797.004.patch, HDFS-10797.005.patch,
> HDFS-10797.006.patch, HDFS-10797.007.patch
>
>
> DirectoryWithSnapshotFeature.computeContentSummary4Snapshot calculates how
> much disk usage is used by a snapshot by tallying up the files in the
> snapshot that have since been deleted (that way it won't overlap with regular
> files whose disk usage is computed separately). However that is determined
> from a diff that shows moved (to Trash or otherwise) or renamed files as a
> deletion and a creation operation that may overlap with the list of blocks.
> Only the deletion operation is taken into consideration, and this causes
> those blocks to get represented twice in the disk usage tallying.
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