nfs-preserve-unlinked · shipping · also OPEN4_RESULT_PRESERVE_UNLINKED, preserve unlinked

NFS open-file preservation

NFS open-file preservation is the NFSv4.1 OPEN-result promise to retain a file removed while open, including through the server-restart grace period for open reclamation.

RFC 8881 section 18.16.3 defines the capability; a version label alone does not show that it was returned. [3] Linux v6.12 records the result on the inode and uses it to bypass the silly-rename branch. [1] [2] Erratum 6865 identifies contradictory REMOVE wording; its status was Reported, not Verified, on 2026-10-16. [4]

Relations

related

nfs-storage, nfs-silly-rename, unlink, nfs-delegation

Advantages

• Moves the advertised open-file lifetime guarantee to the server rather than relying solely on a client's temporary name.

Limitations

• Not proof of data-write durability, indefinite retention or a successful reclaim.
• Client implementation, server behavior and returned flags must be evaluated together.

Citations

1. Linux v6.12, fs/nfs/nfs4proc.c: _nfs4_do_open records the server's preservation flag. (accessed 2026-10-16)
2. Linux v6.12, fs/nfs/dir.c: nfs_unlink gates silly rename on the inode preservation flag. (accessed 2026-10-16)
3. D. Noveck and C. Lever (editors). RFC 8881, sections 18.16.3 and 18.25.4: OPEN and REMOVE. (accessed 2026-10-16)
4. RFC 8881 technical erratum 6865, reported by David Noveck on 2022-02-28; status Reported when checked. (accessed 2026-10-16)
5. Why deleted NFS files become .nfs files (accessed 2026-10-16)

JSON: /data/terms/nfs-preserve-unlinked.json