Return true if this JM can roll back to the previous storage state, false
otherwise. The NN will ref
Close the journal manager, freeing any resources it may hold.
Discard the segments whose first txid is >= the given txid.
Finalize the upgrade. JMs should purge any state that they had been keeping
around during the upgrad
Perform any steps that must succeed across all JournalManagers involved in an
upgrade before proceed
Perform the rollback to the previous FS state. JMs which do not need to roll
back their state should
Perform the actual upgrade of the JM. After this is completed, the NN can begin
to use the new upgra
Mark the log segment that spans from firstTxId to lastTxId as finalized and
Format the underlying storage, removing any previously stored data.
Recover segments which have not been finalized.