[LU-16716] add test to verify irreparable OI mapping

• Type: Improvement
• Resolution: Unresolved
• Priority: Minor
• Assignee: Lai Siyao
• Reporter: Lai Siyao

Description

OI scrub is able to handle mapping in below cases:

• get inode or LMA xattr fail (return code is not -ENOENT, -ESTALE or -ENOMEM).
• FID provided by client is not seen in inode iteration, this happens when client get FID by readdir, but this FID doesn't point to any inode on disk.
• OI scrub found the correct mapping, but fails to update OI files.

Add tests for these cases to ensure they are always correctly handled. And the code of osd_fid_lookup() can be cleaned up to make it easier to understand and maintain.