diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 855add6..bc3a862 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -56,6 +56,30 @@
 static LIST_HEAD(nfs_client_list);
 static LIST_HEAD(nfs_volume_list);
 static DECLARE_WAIT_QUEUE_HEAD(nfs_client_active_wq);
+#ifdef CONFIG_NFS_V4
+static DEFINE_IDR(cb_ident_idr); /* Protected by nfs_client_lock */
+
+/*
+ * Get a unique NFSv4.0 callback identifier which will be used
+ * by the V4.0 callback service to lookup the nfs_client struct
+ */
+static int nfs_get_cb_ident_idr(struct nfs_client *clp, int minorversion)
+{
+	int ret = 0;
+
+	if (clp->rpc_ops->version != 4 || minorversion != 0)
+		return ret;
+retry:
+	if (!idr_pre_get(&cb_ident_idr, GFP_KERNEL))
+		return -ENOMEM;
+	spin_lock(&nfs_client_lock);
+	ret = idr_get_new(&cb_ident_idr, clp, &clp->cl_cb_ident);
+	spin_unlock(&nfs_client_lock);
+	if (ret == -EAGAIN)
+		goto retry;
+	return ret;
+}
+#endif /* CONFIG_NFS_V4 */
 
 /*
  * RPC cruft for NFS
@@ -144,6 +168,10 @@
 	clp->cl_proto = cl_init->proto;
 
 #ifdef CONFIG_NFS_V4
+	err = nfs_get_cb_ident_idr(clp, cl_init->minorversion);
+	if (err)
+		goto error_cleanup;
+
 	INIT_LIST_HEAD(&clp->cl_delegations);
 	spin_lock_init(&clp->cl_lock);
 	INIT_DELAYED_WORK(&clp->cl_renewd, nfs4_renew_state);
@@ -202,10 +230,32 @@
 
 	rpc_destroy_wait_queue(&clp->cl_rpcwaitq);
 }
+
+/* idr_remove_all is not needed as all id's are removed by nfs_put_client */
+void nfs_cleanup_cb_ident_idr(void)
+{
+	idr_destroy(&cb_ident_idr);
+}
+
+/* nfs_client_lock held */
+static void nfs_cb_idr_remove_locked(struct nfs_client *clp)
+{
+	if (clp->cl_cb_ident)
+		idr_remove(&cb_ident_idr, clp->cl_cb_ident);
+}
+
 #else
 static void nfs4_shutdown_client(struct nfs_client *clp)
 {
 }
+
+void nfs_cleanup_cb_ident_idr(void)
+{
+}
+
+static void nfs_cb_idr_remove_locked(struct nfs_client *clp)
+{
+}
 #endif /* CONFIG_NFS_V4 */
 
 /*
@@ -244,6 +294,7 @@
 
 	if (atomic_dec_and_lock(&clp->cl_count, &nfs_client_lock)) {
 		list_del(&clp->cl_share_link);
+		nfs_cb_idr_remove_locked(clp);
 		spin_unlock(&nfs_client_lock);
 
 		BUG_ON(!list_empty(&clp->cl_superblocks));