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https://issues.apache.org/jira/browse/HDFS-15346?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17128305#comment-17128305
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Jinglun commented on HDFS-15346:
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Hi [~linyiqun], thanks your great comments and valuable suggestions ! I'll
need some time to shoot all of them. So let me respond to the question first.
{quote}Here we reset permission to 0, that means no any operation is allowed?
Is this expected, why not is 400 (only allow read)? The comment said that
'cancelling the x permission of the source path.' makes me confused.
{quote}
Yes here we reset the permission to 0. Both read and write in the source path
and all its sub-paths are denied. As far as I know all the read operations need
to check its parents' execution permission. So setting to 400 can't make it
only allowing read. We still can't read its sub-paths. I think the only way to
make it 'only allowing read' is to recursively reduce each directory's
permission to 555. Reduce permission means: if the original permission is 777
then change it to 555. If the original permission is 700 then make it to 500.
Saving all the directories' permissions is very expensive. A better way may be
letting the NameNode to support 'readonly-directory'. I think we can first
using the '0 permission' way to make sure the data is consistent. Then start a
sub-task to enable the NameNode 'readonly-directory'. Finally change this to
the NameNode 'readonly-directory'.
> RBF: DistCpFedBalance implementation
> ------------------------------------
>
> Key: HDFS-15346
> URL: https://issues.apache.org/jira/browse/HDFS-15346
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Jinglun
> Assignee: Jinglun
> Priority: Major
> Attachments: HDFS-15346.001.patch, HDFS-15346.002.patch,
> HDFS-15346.003.patch, HDFS-15346.004.patch, HDFS-15346.005.patch,
> HDFS-15346.006.patch, HDFS-15346.007.patch
>
>
> Patch in HDFS-15294 is too big to review so we split it into 2 patches. This
> is the second one. Detail can be found at HDFS-15294.
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