diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
index 5f07a0ed9188efbddd6e57cecf64cddb6fc4b1c4..03311259b0c45c88de37122cffc0f28c8f6c7e63 100644
--- a/fs/nfs/nfs4client.c
+++ b/fs/nfs/nfs4client.c
@@ -241,28 +241,25 @@ void nfs4_free_client(struct nfs_client *clp)
  */
 static int nfs4_init_callback(struct nfs_client *clp)
 {
+	struct rpc_xprt *xprt;
 	int error;
 
-	if (clp->rpc_ops->version == 4) {
-		struct rpc_xprt *xprt;
+	xprt = rcu_dereference_raw(clp->cl_rpcclient->cl_xprt);
 
-		xprt = rcu_dereference_raw(clp->cl_rpcclient->cl_xprt);
-
-		if (nfs4_has_session(clp)) {
-			error = xprt_setup_backchannel(xprt,
-						NFS41_BC_MIN_CALLBACKS);
-			if (error < 0)
-				return error;
-		}
-
-		error = nfs_callback_up(clp->cl_mvops->minor_version, xprt);
-		if (error < 0) {
-			dprintk("%s: failed to start callback. Error = %d\n",
-				__func__, error);
+	if (nfs4_has_session(clp)) {
+		error = xprt_setup_backchannel(xprt, NFS41_BC_MIN_CALLBACKS);
+		if (error < 0)
 			return error;
-		}
-		__set_bit(NFS_CS_CALLBACK, &clp->cl_res_state);
 	}
+
+	error = nfs_callback_up(clp->cl_mvops->minor_version, xprt);
+	if (error < 0) {
+		dprintk("%s: failed to start callback. Error = %d\n",
+			__func__, error);
+		return error;
+	}
+	__set_bit(NFS_CS_CALLBACK, &clp->cl_res_state);
+
 	return 0;
 }
 
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 03d0fa62a06ec6b0187c5b3b00dad0c47598c393..cb4376b78ed91771b98bf03695eea1c67a5b5889 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -141,13 +141,15 @@ static int nfs4_stat_to_errno(int);
 				XDR_QUADLEN(NFS4_VERIFIER_SIZE) + \
 				XDR_QUADLEN(NFS4_SETCLIENTID_NAMELEN) + \
 				1 /* sc_prog */ + \
-				XDR_QUADLEN(RPCBIND_MAXNETIDLEN) + \
-				XDR_QUADLEN(RPCBIND_MAXUADDRLEN) + \
+				1 + XDR_QUADLEN(RPCBIND_MAXNETIDLEN) + \
+				1 + XDR_QUADLEN(RPCBIND_MAXUADDRLEN) + \
 				1) /* sc_cb_ident */
 #define decode_setclientid_maxsz \
 				(op_decode_hdr_maxsz + \
-				2 + \
-				1024) /* large value for CLID_INUSE */
+				2 /* clientid */ + \
+				XDR_QUADLEN(NFS4_VERIFIER_SIZE) + \
+				1 + XDR_QUADLEN(RPCBIND_MAXNETIDLEN) + \
+				1 + XDR_QUADLEN(RPCBIND_MAXUADDRLEN))
 #define encode_setclientid_confirm_maxsz \
 				(op_encode_hdr_maxsz + \
 				3 + (NFS4_VERIFIER_SIZE >> 2))
diff --git a/include/linux/sunrpc/metrics.h b/include/linux/sunrpc/metrics.h
index 1565bbe86d51e77c2323ca26a04bbad8a35b9f22..eecb5a71e6c0e4362a502a608ebfa179c975f808 100644
--- a/include/linux/sunrpc/metrics.h
+++ b/include/linux/sunrpc/metrics.h
@@ -27,10 +27,13 @@
 
 #include <linux/seq_file.h>
 #include <linux/ktime.h>
+#include <linux/spinlock.h>
 
 #define RPC_IOSTATS_VERS	"1.0"
 
 struct rpc_iostats {
+	spinlock_t		om_lock;
+
 	/*
 	 * These counters give an idea about how many request
 	 * transmissions are required, on average, to complete that
diff --git a/net/sunrpc/stats.c b/net/sunrpc/stats.c
index 54530490944e8a9bbb49e12e1d620f183b0e012d..9711a155bc50071995402518d1ddd56a78b24a2a 100644
--- a/net/sunrpc/stats.c
+++ b/net/sunrpc/stats.c
@@ -116,7 +116,15 @@ EXPORT_SYMBOL_GPL(svc_seq_show);
  */
 struct rpc_iostats *rpc_alloc_iostats(struct rpc_clnt *clnt)
 {
-	return kcalloc(clnt->cl_maxproc, sizeof(struct rpc_iostats), GFP_KERNEL);
+	struct rpc_iostats *stats;
+	int i;
+
+	stats = kcalloc(clnt->cl_maxproc, sizeof(*stats), GFP_KERNEL);
+	if (stats) {
+		for (i = 0; i < clnt->cl_maxproc; i++)
+			spin_lock_init(&stats[i].om_lock);
+	}
+	return stats;
 }
 EXPORT_SYMBOL_GPL(rpc_alloc_iostats);
 
@@ -135,20 +143,21 @@ EXPORT_SYMBOL_GPL(rpc_free_iostats);
  * rpc_count_iostats - tally up per-task stats
  * @task: completed rpc_task
  * @stats: array of stat structures
- *
- * Relies on the caller for serialization.
  */
 void rpc_count_iostats(const struct rpc_task *task, struct rpc_iostats *stats)
 {
 	struct rpc_rqst *req = task->tk_rqstp;
 	struct rpc_iostats *op_metrics;
-	ktime_t delta;
+	ktime_t delta, now;
 
 	if (!stats || !req)
 		return;
 
+	now = ktime_get();
 	op_metrics = &stats[task->tk_msg.rpc_proc->p_statidx];
 
+	spin_lock(&op_metrics->om_lock);
+
 	op_metrics->om_ops++;
 	op_metrics->om_ntrans += req->rq_ntrans;
 	op_metrics->om_timeouts += task->tk_timeouts;
@@ -161,8 +170,10 @@ void rpc_count_iostats(const struct rpc_task *task, struct rpc_iostats *stats)
 
 	op_metrics->om_rtt = ktime_add(op_metrics->om_rtt, req->rq_rtt);
 
-	delta = ktime_sub(ktime_get(), task->tk_start);
+	delta = ktime_sub(now, task->tk_start);
 	op_metrics->om_execute = ktime_add(op_metrics->om_execute, delta);
+
+	spin_unlock(&op_metrics->om_lock);
 }
 EXPORT_SYMBOL_GPL(rpc_count_iostats);