nfsd: disable deferral for NFSv4

Now that a slight delay in getting a reply to an upcall doesn't
require deferring of requests, request deferral for all NFSv4
requests - the concept doesn't really fit with the v4 model.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4proc.c

@@ -1031,8 +1031,11 @@ nfsd4_proc_compound(struct svc_rqst *rqstp,
 	resp->cstate.session = NULL;
 	fh_init(&resp->cstate.current_fh, NFS4_FHSIZE);
 	fh_init(&resp->cstate.save_fh, NFS4_FHSIZE);
-	/* Use the deferral mechanism only for NFSv4.0 compounds */
-	rqstp->rq_usedeferral = (args->minorversion == 0);
+	/*
+	 * Don't use the deferral mechanism for NFSv4; compounds make it
+	 * too hard to avoid non-idempotency problems.
+	 */
+	rqstp->rq_usedeferral = 0;
 
 	/*
 	 * According to RFC3010, this takes precedence over all other errors.