[LU-7619] USE_LU_REF/lu_ref feature broken after some REFASSERT()s have been added without lu_ref::lf_guard protection

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.9.0
• Severity: 3
• Assignee: Bruno Faccini (Inactive)
• Reporter: Bruno Faccini (Inactive)

Description

Some quite old patches have introduced several REFASSERT()s, to strengthen lu_ref feature controls, but not under required lu_ref::lf_guard spin-lock protection.
This can cause unexpected "self" dead-lock situations (vs LBUG/ASSERT!!) upon lu_ref failure detection.
This has been unveiled during my own usage of the feature to track and debug some unreferencing bug/lack.