HDFS-10899 disables renames within the EZ if it's under re-encryption. (similar to current cross-zone rename checks).
We'd like to support rename in the long run, so cluster is fully functioning during re-encryption.
The reason rename is particularly difficult is:
- We want to re-encrypt all files under an EZ in one pass, without missing any
- We want to iterate through the files and keep track of where we are (i.e. a cursor), so in case of NN failover/crash, we can resume from fsimage/edits.
- We cannot guarantee namespace is not changed during re-encryption. Newly created files automatically has new edek, deleted files we don't care. But if a file is renamed from behind the cursor to before, it may be missed in the re-encryption.