NFSD: keep track of the number of v4 clients in the system

Add counter nfs4_client_count to keep track of the total number
of v4 clients, including courtesy clients, in the system.
Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/netns.h

@@ -189,6 +189,8 @@ struct nfsd_net {
 	struct nfsd_fcache_disposal *fcache_disposal;
 
 	siphash_key_t		siphash_key;
+
+	atomic_t		nfs4_client_count;
 };
 
 /* Simple check to find out if a given net was properly initialized */

fs/nfsd/nfs4state.c

@@ -2053,7 +2053,8 @@ STALE_CLIENTID(clientid_t *clid, struct nfsd_net *nn)
  * This type of memory management is somewhat inefficient, but we use it
  * anyway since SETCLIENTID is not a common operation.
  */
-static struct nfs4_client *alloc_client(struct xdr_netobj name)
+static struct nfs4_client *alloc_client(struct xdr_netobj name,
+				struct nfsd_net *nn)
 {
 	struct nfs4_client *clp;
 	int i;
@@ -2076,6 +2077,7 @@ static struct nfs4_client *alloc_client(struct xdr_netobj name)
 	atomic_set(&clp->cl_rpc_users, 0);
 	clp->cl_cb_state = NFSD4_CB_UNKNOWN;
 	clp->cl_state = NFSD4_ACTIVE;
+	atomic_inc(&nn->nfs4_client_count);
 	atomic_set(&clp->cl_delegs_in_recall, 0);
 	INIT_LIST_HEAD(&clp->cl_idhash);
 	INIT_LIST_HEAD(&clp->cl_openowners);
@@ -2183,6 +2185,7 @@ static __be32 mark_client_expired_locked(struct nfs4_client *clp)
 static void
 __destroy_client(struct nfs4_client *clp)
 {
+	struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
 	int i;
 	struct nfs4_openowner *oo;
 	struct nfs4_delegation *dp;
@@ -2226,6 +2229,7 @@ __destroy_client(struct nfs4_client *clp)
 	nfsd4_shutdown_callback(clp);
 	if (clp->cl_cb_conn.cb_xprt)
 		svc_xprt_put(clp->cl_cb_conn.cb_xprt);
+	atomic_add_unless(&nn->nfs4_client_count, -1, 0);
 	free_client(clp);
 	wake_up_all(&expiry_wq);
 }
@@ -2848,7 +2852,7 @@ static struct nfs4_client *create_client(struct xdr_netobj name,
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 	struct dentry *dentries[ARRAY_SIZE(client_files)];
 
-	clp = alloc_client(name);
+	clp = alloc_client(name, nn);
 	if (clp == NULL)
 		return NULL;
 
@@ -4340,6 +4344,8 @@ void nfsd4_init_leases_net(struct nfsd_net *nn)
 	nn->clientid_base = prandom_u32();
 	nn->clientid_counter = nn->clientid_base + 1;
 	nn->s2s_cp_cl_id = nn->clientid_counter++;
+
+	atomic_set(&nn->nfs4_client_count, 0);
 }
 
 static void init_nfs4_replay(struct nfs4_replay *rp)