nfsd: don't use the deferral service, return NFS4ERR_DELAY

On an NFSv4.1 server cache miss that causes an upcall, NFS4ERR_DELAY will be
returned. It is up to the NFSv4.1 client to resend only the operations that
have not been processed.

Initialize rq_usedeferral to 1 in svc_process(). It sill be turned off in
nfsd4_proc_compound() only when NFSv4.1 Sessions are used.

Note: this isn't an adequate solution on its own. It's acceptable as a way
to get some minimal 4.1 up and working, but we're going to have to find a
way to avoid returning DELAY in all common cases before 4.1 can really be
considered ready.

Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
[nfsd41: reverse rq_nodeferral negative logic]
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
[sunrpc: initialize rq_usedeferral]
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

fs/nfsd/nfs4proc.c

@@ -854,6 +854,8 @@ nfsd4_proc_compound(struct svc_rqst *rqstp,
 	resp->cstate.replay_owner = 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);
 
 	/*
 	 * According to RFC3010, this takes precedence over all other errors.
@@ -933,12 +935,18 @@ nfsd4_proc_compound(struct svc_rqst *rqstp,
 
 		nfsd4_increment_op_stats(op->opnum);
 	}
+	if (!rqstp->rq_usedeferral && status == nfserr_dropit) {
+		dprintk("%s Dropit - send NFS4ERR_DELAY\n", __func__);
+		status = nfserr_jukebox;
+	}
 
 	fh_put(&resp->cstate.current_fh);
 	fh_put(&resp->cstate.save_fh);
 	BUG_ON(resp->cstate.replay_owner);
 out:
 	nfsd4_release_compoundargs(args);
+	/* Reset deferral mechanism for RPC deferrals */
+	rqstp->rq_usedeferral = 1;
 	dprintk("nfsv4 compound returned %d\n", ntohl(status));
 	return status;
 }

include/linux/sunrpc/svc.h

@@ -230,6 +230,7 @@ struct svc_rqst {
 	struct svc_cred		rq_cred;	/* auth info */
 	void *			rq_xprt_ctxt;	/* transport specific context ptr */
 	struct svc_deferred_req*rq_deferred;	/* deferred request we are replaying */
+	int			rq_usedeferral;	/* use deferral */
 
 	size_t			rq_xprt_hlen;	/* xprt header len */
 	struct xdr_buf		rq_arg;

net/sunrpc/svc.c

@@ -1023,6 +1023,8 @@ svc_process(struct svc_rqst *rqstp)
 	rqstp->rq_res.tail[0].iov_len = 0;
 	/* Will be turned off only in gss privacy case: */
 	rqstp->rq_splice_ok = 1;
+	/* Will be turned off only when NFSv4 Sessions are used */
+	rqstp->rq_usedeferral = 1;
 
 	/* Setup reply header */
 	rqstp->rq_xprt->xpt_ops->xpo_prep_reply_hdr(rqstp);

net/sunrpc/svc_xprt.c

@@ -974,7 +974,7 @@ static struct cache_deferred_req *svc_defer(struct cache_req *req)
 	struct svc_rqst *rqstp = container_of(req, struct svc_rqst, rq_chandle);
 	struct svc_deferred_req *dr;
 
-	if (rqstp->rq_arg.page_len)
+	if (rqstp->rq_arg.page_len || !rqstp->rq_usedeferral)
 		return NULL; /* if more than a page, give up FIXME */
 	if (rqstp->rq_deferred) {
 		dr = rqstp->rq_deferred;