HDFS-16733.Improve INode#isRoot(). #4761
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jianghuazhu
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Can you help review this pr, @jojochuang @virajjasani @Hexiaoqiao . |
Hexiaoqiao
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Aug 23, 2022
| @@ -73,7 +73,8 @@ public abstract class INode implements INodeAttributes, Diff.Element<byte[]> { | |||
| * Check whether this is the root inode. | |||
| */ | |||
| final boolean isRoot() { | |||
| return getLocalNameBytes().length == 0; | |||
| // Note: There is no restriction that id must be equal to INodeId#ROOT_INODE_ID | |||
| return getLocalNameBytes() == null || getLocalNameBytes().length == 0; | |||
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Sorry I did not get why change here. IIUC, ROOT_NAME is not null but empty string, right? If that, I think it will not throw NPE here. So any information I missed? Thanks @jianghuazhu .
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@Hexiaoqiao , thanks for your comment and review.
I found this question while exploring the FGL module.
In the FGL module, INodeMap#INodeMap() runs the name is null when constructing the INodeDirectory. Here: https://github.com/apache/hadoop/blob/fgl/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodeMap.java
When verifying the lease, INode#isRoot() is called. See here:
https://github.com/apache/hadoop/blob/fgl/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
Calling link: FSNamesystem#checkLease()->isFileDeleted()->INode#isRoot().
I think this is a hidden problem because we didn't allow INodeWithAdditionalFields#name to always be an empty string.
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Got it. If that is true, I think we should submit PR to branch FGL first? Thanks.
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Thanks @Hexiaoqiao .
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Description of PR
When constructing an INodeFile or INodeDirectory, if the given name is null, an exception will be thrown when checking whether it is root.
Details: HDFS-16733
How was this patch tested?
When constructing an INodeFile or INodeDirectory, if the given name is null, an exception will not occur when checking whether it is root.