ipvs: convert locks used in persistence engines

Allow the readers to use RCU lock and for
PE module registrations use global mutex instead of
spinlock. All PE modules need to use synchronize_rcu
in their module exit handler.
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off by: Hans Schillstrom <hans@schillstrom.com>
Signed-off-by: Simon Horman <horms@verge.net.au>

net/netfilter/ipvs/ip_vs_pe.c

@@ -13,8 +13,8 @@
 /* IPVS pe list */
 static LIST_HEAD(ip_vs_pe);
 
-/* lock for service table */
-static DEFINE_SPINLOCK(ip_vs_pe_lock);
+/* semaphore for IPVS PEs. */
+static DEFINE_MUTEX(ip_vs_pe_mutex);
 
 /* Bind a service with a pe */
 void ip_vs_bind_pe(struct ip_vs_service *svc, struct ip_vs_pe *pe)
@@ -36,9 +36,8 @@ struct ip_vs_pe *__ip_vs_pe_getbyname(const char *pe_name)
 	IP_VS_DBG(10, "%s(): pe_name \"%s\"\n", __func__,
 		  pe_name);
 
-	spin_lock_bh(&ip_vs_pe_lock);
-
-	list_for_each_entry(pe, &ip_vs_pe, n_list) {
+	rcu_read_lock();
+	list_for_each_entry_rcu(pe, &ip_vs_pe, n_list) {
 		/* Test and get the modules atomically */
 		if (pe->module &&
 		    !try_module_get(pe->module)) {
@@ -47,14 +46,14 @@ struct ip_vs_pe *__ip_vs_pe_getbyname(const char *pe_name)
 		}
 		if (strcmp(pe_name, pe->name)==0) {
 			/* HIT */
-			spin_unlock_bh(&ip_vs_pe_lock);
+			rcu_read_unlock();
 			return pe;
 		}
 		if (pe->module)
 			module_put(pe->module);
 	}
+	rcu_read_unlock();
 
-	spin_unlock_bh(&ip_vs_pe_lock);
 	return NULL;
 }
 
@@ -83,22 +82,13 @@ int register_ip_vs_pe(struct ip_vs_pe *pe)
 	/* increase the module use count */
 	ip_vs_use_count_inc();
 
-	spin_lock_bh(&ip_vs_pe_lock);
-
-	if (!list_empty(&pe->n_list)) {
-		spin_unlock_bh(&ip_vs_pe_lock);
-		ip_vs_use_count_dec();
-		pr_err("%s(): [%s] pe already linked\n",
-		       __func__, pe->name);
-		return -EINVAL;
-	}
-
+	mutex_lock(&ip_vs_pe_mutex);
 	/* Make sure that the pe with this name doesn't exist
 	 * in the pe list.
 	 */
 	list_for_each_entry(tmp, &ip_vs_pe, n_list) {
 		if (strcmp(tmp->name, pe->name) == 0) {
-			spin_unlock_bh(&ip_vs_pe_lock);
+			mutex_unlock(&ip_vs_pe_mutex);
 			ip_vs_use_count_dec();
 			pr_err("%s(): [%s] pe already existed "
 			       "in the system\n", __func__, pe->name);
@@ -106,8 +96,8 @@ int register_ip_vs_pe(struct ip_vs_pe *pe)
 		}
 	}
 	/* Add it into the d-linked pe list */
-	list_add(&pe->n_list, &ip_vs_pe);
-	spin_unlock_bh(&ip_vs_pe_lock);
+	list_add_rcu(&pe->n_list, &ip_vs_pe);
+	mutex_unlock(&ip_vs_pe_mutex);
 
 	pr_info("[%s] pe registered.\n", pe->name);
 
@@ -118,17 +108,10 @@ EXPORT_SYMBOL_GPL(register_ip_vs_pe);
 /* Unregister a pe from the pe list */
 int unregister_ip_vs_pe(struct ip_vs_pe *pe)
 {
-	spin_lock_bh(&ip_vs_pe_lock);
-	if (list_empty(&pe->n_list)) {
-		spin_unlock_bh(&ip_vs_pe_lock);
-		pr_err("%s(): [%s] pe is not in the list. failed\n",
-		       __func__, pe->name);
-		return -EINVAL;
-	}
-
+	mutex_lock(&ip_vs_pe_mutex);
 	/* Remove it from the d-linked pe list */
-	list_del(&pe->n_list);
-	spin_unlock_bh(&ip_vs_pe_lock);
+	list_del_rcu(&pe->n_list);
+	mutex_unlock(&ip_vs_pe_mutex);
 
 	/* decrease the module use count */
 	ip_vs_use_count_dec();

net/netfilter/ipvs/ip_vs_pe_sip.c

@@ -172,6 +172,7 @@ static int __init ip_vs_sip_init(void)
 static void __exit ip_vs_sip_cleanup(void)
 {
 	unregister_ip_vs_pe(&ip_vs_sip_pe);
+	synchronize_rcu();
 }
 
 module_init(ip_vs_sip_init);