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https://issues.apache.org/jira/browse/HDFS-3981?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13464515#comment-13464515
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Konstantin Shvachko commented on HDFS-3981:
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Xiaobo, you are right this seems to be the problem. It actually even worth,
because {{getBlockLocations()}} is forced to change read lock to write lock
every time when times don't need to be updated, which is supposed to be the
main fork-flow.
I traced this problem back all the way to 0.22 version. So I made this issue
targeted for 0.23.4.
I put a short summary in the description field, and moved your detailed one to
the previous comment. Please follow this practice in the future as the
description is emailed with every jira comment or update.
> access time is set without holding writelock in FSNamesystem
> ------------------------------------------------------------
>
> Key: HDFS-3981
> URL: https://issues.apache.org/jira/browse/HDFS-3981
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: name-node
> Affects Versions: 0.23.3
> Reporter: Xiaobo Peng
> Assignee: Xiaobo Peng
> Priority: Minor
>
> Incorrect condition in {{FSNamesystem.getBlockLocatoins()}} can lead to
> updating times without write lock. In most cases this condition will force
> {{FSNamesystem.getBlockLocatoins()}} to hold write lock, even if times do not
> need to be updated.
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