sunrpc: don't change ->sv_stats if it doesn't exist

We check for the existence of ->sv_stats elsewhere except in the core
processing code.  It appears that only nfsd actual exports these values
anywhere, everybody else just has a write only copy of sv_stats in their
svc_program.  Add a check for ->sv_stats before every adjustment to
allow us to eliminate the stats struct from all the users who don't
report the stats.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

net/sunrpc/svc.c

@@ -1375,6 +1375,7 @@ svc_process_common(struct svc_rqst *rqstp)
 		goto err_bad_proc;
 
 	/* Syntactic check complete */
+	if (serv->sv_stats)
 		serv->sv_stats->rpccnt++;
 	trace_svc_process(rqstp, progp->pg_name);
 
@@ -1427,6 +1428,7 @@ svc_process_common(struct svc_rqst *rqstp)
 	goto close_xprt;
 
 err_bad_rpc:
+	if (serv->sv_stats)
 		serv->sv_stats->rpcbadfmt++;
 	xdr_stream_encode_u32(xdr, RPC_MSG_DENIED);
 	xdr_stream_encode_u32(xdr, RPC_MISMATCH);
@@ -1438,6 +1440,7 @@ svc_process_common(struct svc_rqst *rqstp)
 err_bad_auth:
 	dprintk("svc: authentication failed (%d)\n",
 		be32_to_cpu(rqstp->rq_auth_stat));
+	if (serv->sv_stats)
 		serv->sv_stats->rpcbadauth++;
 	/* Restore write pointer to location of reply status: */
 	xdr_truncate_encode(xdr, XDR_UNIT * 2);
@@ -1448,6 +1451,7 @@ svc_process_common(struct svc_rqst *rqstp)
 
 err_bad_prog:
 	dprintk("svc: unknown program %d\n", rqstp->rq_prog);
+	if (serv->sv_stats)
 		serv->sv_stats->rpcbadfmt++;
 	*rqstp->rq_accept_statp = rpc_prog_unavail;
 	goto sendit;
@@ -1456,6 +1460,7 @@ svc_process_common(struct svc_rqst *rqstp)
 	svc_printk(rqstp, "unknown version (%d for prog %d, %s)\n",
 		       rqstp->rq_vers, rqstp->rq_prog, progp->pg_name);
 
+	if (serv->sv_stats)
 		serv->sv_stats->rpcbadfmt++;
 	*rqstp->rq_accept_statp = rpc_prog_mismatch;
 
@@ -1470,6 +1475,7 @@ svc_process_common(struct svc_rqst *rqstp)
 err_bad_proc:
 	svc_printk(rqstp, "unknown procedure (%d)\n", rqstp->rq_proc);
 
+	if (serv->sv_stats)
 		serv->sv_stats->rpcbadfmt++;
 	*rqstp->rq_accept_statp = rpc_proc_unavail;
 	goto sendit;
@@ -1477,11 +1483,13 @@ svc_process_common(struct svc_rqst *rqstp)
 err_garbage_args:
 	svc_printk(rqstp, "failed to decode RPC header\n");
 
+	if (serv->sv_stats)
 		serv->sv_stats->rpcbadfmt++;
 	*rqstp->rq_accept_statp = rpc_garbage_args;
 	goto sendit;
 
 err_system_err:
+	if (serv->sv_stats)
 		serv->sv_stats->rpcbadfmt++;
 	*rqstp->rq_accept_statp = rpc_system_err;
 	goto sendit;
@@ -1534,6 +1542,7 @@ void svc_process(struct svc_rqst *rqstp)
 out_baddir:
 	svc_printk(rqstp, "bad direction 0x%08x, dropping request\n",
 		   be32_to_cpu(*p));
+	if (rqstp->rq_server->sv_stats)
 		rqstp->rq_server->sv_stats->rpcbadfmt++;
 out_drop:
 	svc_drop(rqstp);