nfsd4: send the special close_stateid in v4.0 replies as well

We already send it for v4.1, but RFC7530 also notes that the stateid in
the close reply is bogus.

Always send the special close stateid, even in v4.0 responses. No client
should put any meaning on it whatsoever. For now, we continue to
increment the stateid value, though that might not be necessary either.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4state.c

@@ -5521,15 +5521,26 @@ nfsd4_close(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 		goto out; 
 
 	stp->st_stid.sc_type = NFS4_CLOSED_STID;
+
+	/*
+	 * Technically we don't _really_ have to increment or copy it, since
+	 * it should just be gone after this operation and we clobber the
+	 * copied value below, but we continue to do so here just to ensure
+	 * that racing ops see that there was a state change.
+	 */
 	nfs4_inc_and_copy_stateid(&close->cl_stateid, &stp->st_stid);
 
 	nfsd4_close_open_stateid(stp);
 	mutex_unlock(&stp->st_mutex);
 
-	/* See RFC5661 sectionm 18.2.4 */
-	if (stp->st_stid.sc_client->cl_minorversion)
-		memcpy(&close->cl_stateid, &close_stateid,
-				sizeof(close->cl_stateid));
+	/* v4.1+ suggests that we send a special stateid in here, since the
+	 * clients should just ignore this anyway. Since this is not useful
+	 * for v4.0 clients either, we set it to the special close_stateid
+	 * universally.
+	 *
+	 * See RFC5661 section 18.2.4, and RFC7530 section 16.2.5
+	 */
+	memcpy(&close->cl_stateid, &close_stateid, sizeof(close->cl_stateid));
 
 	/* put reference from nfs4_preprocess_seqid_op */
 	nfs4_put_stid(&stp->st_stid);