RFC 7530, "Network File System (NFS) Version 4 Protocol", March 2015

Note: This RFC has been updated by RFC 7931, RFC 8587

Errata ID: 5407
Status: Reported
Type: Technical
Publication Format(s) : TEXT
Reported By: Viral Mehta
Date Reported: 2018-06-24

Section 16.36 says:

The write
   verifier is a cookie that the client can use to determine whether the
   server has changed instance (boot) state between a call to WRITE and
   a subsequent call to either WRITE or COMMIT.  This cookie must be
   consistent during a single instance of the NFSv4 protocol service and
   must be unique between instances of the NFSv4 protocol server, where
   uncommitted data may be lost.

It should say:

The write
   verifier is a cookie that the client can use to determine whether the
   server has changed instance (boot) state between a call to WRITE and
   a subsequent call to either WRITE or COMMIT.  This cookie must be
   consistent during a single instance of the NFSv4 protocol service and
   must be unique between instances of the NFSv4 protocol server, where
   uncommitted data may be lost. The server implementation should not
   assume that the cookie is on per file basis.

Notes:

Different NFS client implementation has chosen to interpret above statement differently. Semantically, it is correct to track cookie on per file basis since both WRITE and COMMIT happens on a single file handle. But, RFC wording says that the cookie should be maintained on a per server instance basis. Either way, I believe the RFC can be more clearer for both client and server implementer.

Report New Errata