[LU-8808] Concurrent update during file restore can lead to disordered changelog sequence

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.10.0
• Severity: 3
• Assignee: Bruno Faccini (Inactive)
• Reporter: Bruno Faccini (Inactive)

Description

In hsm_cdt_request_completed(), upon restore completion, layout lock is returned before associated ChangeLog entry has been created.
This allows for a timing window where concurrent file updater can take control and create its own ChangeLog out of order (before restore ChangeLog).
This can puzzle, ChangeLog readers (like RobinHood), and have them think of a wrong file state.