[jira] [Created] (HDFS-4877) Snapshot: fix the scenario where a directory is renamed under its prior descendant

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

Jing Zhao created HDFS-4877:
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             Summary: Snapshot: fix the scenario where a directory is renamed under its prior descendant
                 Key: HDFS-4877
                 URL: https://issues.apache.org/jira/browse/HDFS-4877
             Project: Hadoop HDFS
          Issue Type: Bug
    Affects Versions: 3.0.0
            Reporter: Jing Zhao
            Assignee: Jing Zhao
            Priority: Critical


Suppose we have the following operations:
1. rename /dir1/foo/bar to /dir2/bar2
2. rename /dir1/foo to /dir2/bar2/foo2

I.e., we rename a directory (foo) to a child of its prior descendant (bar). If we have taken snapshots on root before the above 2 rename operations, a circle can be generated consisting of nodes with the types INodeReference.WithName and INodeReference.DstReference:

WithName (foo) --> WithCount (for foo) --> foo2 --> WithName (bar) --> WithCount (for bar) --> bar2 --> DstReference (foo) --> WithCount (for foo)

When deleting a snapshot before the rename operations, the current code may hit an infinite loop when cleaning the snapshot data or updating the quota usage for the nodes in the above circle. This jira will fix the issue.



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