KevinWikant commented on PR #4568:
URL: https://github.com/apache/hadoop/pull/4568#issuecomment-1205781950

   Hey Xiaohui, appreciate you taking the time to review this :)
   
   Just wanted to clarify a few things:
   
   ```
   This is a complete unnecessary change. It was mentioned in your last JIRA 
[HDFS-16064](https://issues.apache.org/jira/browse/HDFS-16064) by 
[yanbin.zhang](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=it_singer)
 that you are finding a wrong root cause in that JIRA and you didnt coordinate 
or reply them ?
   ```
   
   I did reply to yanbin.zhang in the JIRA, you can see my comment just under 
theirs. I would also add:
   a) the root cause is correct as per the testing that was conducted
   b) I have seen this issue (i.e. HDFS-16064) impact production Hadoop clusters
   
   ```
   This current change seems to unnecessary. If it would be a real production 
bug , someone in community would have experienced it. It is not like that you 
are reading the code someday and you identified some bug like this. Block 
management is very much critical and unnecessary changes always lead to more 
critical bugs...
   ```
   
   I understand that there is no clear reporting of this issue beforehand by 
the community. That being said, the behavior is reproducible (as per the 
testing details in this PR/JIRA) and the behavior results in block invalidation 
requests (i.e. DNA_INVALIDATE) sent to datanodes failing due to incorrect 
GenerationStamp. I would argue that sending an incorrect GenerationStamp in a 
DNA_INVALIDATE request is a bug because it causes the request to fail when it 
otherwise could have succeeded if the correct GenerationStamp is used.
   
   I would ask that you more clearly articulate why this change is 
un-necessary. Do you believe that sending an incorrect GenerationStamp in a 
DNA_INVALIDATE request causing the request to fail is not a bug? Or do you 
believe that this reproducible behavior should not be addressed simply because 
it has not been frequently reported as production impacting by the community?


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