nfsd: separate nfsd_last_thread() from nfsd_put()

Now that the last nfsd thread is stopped by an explicit act of calling
svc_set_num_threads() with a count of zero, we only have a limited
number of places that can happen, and don't need to call
nfsd_last_thread() in nfsd_put()

So separate that out and call it at the two places where the number of
threads is set to zero.

Move the clearing of ->nfsd_serv and the call to svc_xprt_destroy_all()
into nfsd_last_thread(), as they are really part of the same action.

nfsd_put() is now a thin wrapper around svc_put(), so make it a static
inline.

nfsd_put() cannot be called after nfsd_last_thread(), so in a couple of
places we have to use svc_put() instead.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfsd.h

@@ -96,7 +96,12 @@ int		nfsd_pool_stats_open(struct inode *, struct file *);
 int		nfsd_pool_stats_release(struct inode *, struct file *);
 void		nfsd_shutdown_threads(struct net *net);
 
-void		nfsd_put(struct net *net);
+static inline void nfsd_put(struct net *net)
+{
+	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+
+	svc_put(nn->nfsd_serv);
+}
 
 bool		i_am_nfsd(void);
 

fs/nfsd/nfssvc.c

@@ -542,9 +542,14 @@ static struct notifier_block nfsd_inet6addr_notifier = {
 /* Only used under nfsd_mutex, so this atomic may be overkill: */
 static atomic_t nfsd_notifier_refcount = ATOMIC_INIT(0);
 
-static void nfsd_last_thread(struct svc_serv *serv, struct net *net)
+static void nfsd_last_thread(struct net *net)
 {
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+	struct svc_serv *serv = nn->nfsd_serv;
+
+	spin_lock(&nfsd_notifier_lock);
+	nn->nfsd_serv = NULL;
+	spin_unlock(&nfsd_notifier_lock);
 
 	/* check if the notifier still has clients */
 	if (atomic_dec_return(&nfsd_notifier_refcount) == 0) {
@@ -554,6 +559,8 @@ static void nfsd_last_thread(struct svc_serv *serv, struct net *net)
 #endif
 	}
 
+	svc_xprt_destroy_all(serv, net);
+
 	/*
 	 * write_ports can create the server without actually starting
 	 * any threads--if we get shut down before any threads are
@@ -644,7 +651,8 @@ void nfsd_shutdown_threads(struct net *net)
 	svc_get(serv);
 	/* Kill outstanding nfsd threads */
 	svc_set_num_threads(serv, NULL, 0);
-	nfsd_put(net);
+	nfsd_last_thread(net);
+	svc_put(serv);
 	mutex_unlock(&nfsd_mutex);
 }
 
@@ -674,9 +682,6 @@ int nfsd_create_serv(struct net *net)
 	serv->sv_maxconn = nn->max_connections;
 	error = svc_bind(serv, net);
 	if (error < 0) {
-		/* NOT nfsd_put() as notifiers (see below) haven't
-		 * been set up yet.
-		 */
 		svc_put(serv);
 		return error;
 	}
@@ -719,29 +724,6 @@ int nfsd_get_nrthreads(int n, int *nthreads, struct net *net)
 	return 0;
 }
 
-/* This is the callback for kref_put() below.
- * There is no code here as the first thing to be done is
- * call svc_shutdown_net(), but we cannot get the 'net' from
- * the kref.  So do all the work when kref_put returns true.
- */
-static void nfsd_noop(struct kref *ref)
-{
-}
-
-void nfsd_put(struct net *net)
-{
-	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
-
-	if (kref_put(&nn->nfsd_serv->sv_refcnt, nfsd_noop)) {
-		svc_xprt_destroy_all(nn->nfsd_serv, net);
-		nfsd_last_thread(nn->nfsd_serv, net);
-		svc_destroy(&nn->nfsd_serv->sv_refcnt);
-		spin_lock(&nfsd_notifier_lock);
-		nn->nfsd_serv = NULL;
-		spin_unlock(&nfsd_notifier_lock);
-	}
-}
-
 int nfsd_set_nrthreads(int n, int *nthreads, struct net *net)
 {
 	int i = 0;
@@ -792,7 +774,7 @@ int nfsd_set_nrthreads(int n, int *nthreads, struct net *net)
 		if (err)
 			break;
 	}
-	nfsd_put(net);
+	svc_put(nn->nfsd_serv);
 	return err;
 }
 
@@ -807,6 +789,7 @@ nfsd_svc(int nrservs, struct net *net, const struct cred *cred)
 	int	error;
 	bool	nfsd_up_before;
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
+	struct svc_serv *serv;
 
 	mutex_lock(&nfsd_mutex);
 	dprintk("nfsd: creating service\n");
@@ -826,22 +809,25 @@ nfsd_svc(int nrservs, struct net *net, const struct cred *cred)
 		goto out;
 
 	nfsd_up_before = nn->nfsd_net_up;
+	serv = nn->nfsd_serv;
 
 	error = nfsd_startup_net(net, cred);
 	if (error)
 		goto out_put;
-	error = svc_set_num_threads(nn->nfsd_serv, NULL, nrservs);
+	error = svc_set_num_threads(serv, NULL, nrservs);
 	if (error)
 		goto out_shutdown;
-	error = nn->nfsd_serv->sv_nrthreads;
+	error = serv->sv_nrthreads;
+	if (error == 0)
+		nfsd_last_thread(net);
 out_shutdown:
 	if (error < 0 && !nfsd_up_before)
 		nfsd_shutdown_net(net);
 out_put:
 	/* Threads now hold service active */
 	if (xchg(&nn->keep_active, 0))
-		nfsd_put(net);
-	nfsd_put(net);
+		svc_put(serv);
+	svc_put(serv);
 out:
 	mutex_unlock(&nfsd_mutex);
 	return error;