[LU-4788] LFSCK 3: MDT-MDT consistency verification

• Type: New Feature
• Resolution: Fixed
• Priority: Critical
• Fix Version/s: Lustre 2.7.0
• Labels: LFSCK

Epic

LFSCK

• Project: OpenSFS SFS-DEV-001
• Assignee: nasf (Inactive)
• Reporter: nasf (Inactive)

Description

In LFSCK 3, we will not only extend the FID-in-dirent and linkEA verification from single MDT to cross-MDTs cases, but also some additional inconsistent check/repair for remote object and striped directory, includes:
1) Dangling referenced name entry: The name entry exists, but related MDT-object does not exist.
2) Orphan MDT-object: The MDT-object exists, but there is no name entry to reference it.
3) Multiple-referenced name entry: More than one MDT-objects point back to the same name entry, but the name entry only references one of them.
4) Unmatched name entry and MDT-object pairs: The name entry references the MDT-object which has no linkEA for back-reference or it points back to another name entry that does not exists or does not reference the MDT-object.
5) Redundant or invalid linkEA entries: Repeated linkEA entries, or bad parent FID, or the parent FID is not for MDT-object, or not allocated yet.
6) Invalid nlink count: The MDT-object's nlink count does not matches the name entries (which reference such MDT-object) count.