[LU-19279] Include root FID in debugfs MDT exports

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.17.0
• Severity: 3
• Assignee: Marc Vef
• Reporter: Marc Vef

Description

When clients mount Lustre, the root FID is stored in the client export on the MDT0, which reflects the subdirectory that is currently mounted by the client.

It seems beneficial to expose this information on the MDT server-side through debugfs mdt.TARGET.exports.NID.export. This allows administrators to verify which subdirectory a client has mounted, even if access to the client is not possible.