ipvs: convert dests to rcu

In previous commits the schedulers started to access
svc->destinations with _rcu list traversal primitives
because the IP_VS_WAIT_WHILE macro still plays the role of
grace period. Now it is time to finish the updating part,
i.e. adding and deleting of dests with _rcu suffix before
removing the IP_VS_WAIT_WHILE in next commit.

We use the same rule for conns as for the
schedulers: dests can be searched in RCU read-side critical
section where ip_vs_dest_hold can be called by ip_vs_bind_dest.

Some things are not perfect, for example, calling
functions like ip_vs_lookup_dest from updating code under
RCU, just because we use some function both from reader
and from updater.

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>

3 files changed, 26 insertions, 25 deletions

diff --git a/net/netfilter/ipvs/ip_vs_conn.c b/net/netfilter/ipvs/ip_vs_conn.c
index 1b29e4a2b26c..54de34077b63 100644
--- a/net/netfilter/ipvs/ip_vs_conn.c
+++ b/net/netfilter/ipvs/ip_vs_conn.c
@@ -611,10 +611,11 @@ ip_vs_bind_dest(struct ip_vs_conn *cp, struct ip_vs_dest *dest)
  * Check if there is a destination for the connection, if so
  * bind the connection to the destination.
  */
-struct ip_vs_dest *ip_vs_try_bind_dest(struct ip_vs_conn *cp)
+void ip_vs_try_bind_dest(struct ip_vs_conn *cp)
 {
         struct ip_vs_dest *dest;
 
+        rcu_read_lock();
         dest = ip_vs_find_dest(ip_vs_conn_net(cp), cp->af, &cp->daddr,
                                cp->dport, &cp->vaddr, cp->vport,
                                cp->protocol, cp->fwmark, cp->flags);
@@ -624,7 +625,8 @@ struct ip_vs_dest *ip_vs_try_bind_dest(struct ip_vs_conn *cp)
                 spin_lock(&cp->lock);
                 if (cp->dest) {
                         spin_unlock(&cp->lock);
-                        return dest;
+                        rcu_read_unlock();
+                        return;
                 }
 
                 /* Applications work depending on the forwarding method
@@ -648,7 +650,7 @@ struct ip_vs_dest *ip_vs_try_bind_dest(struct ip_vs_conn *cp)
                 if (pd && atomic_read(&pd->appcnt))
                         ip_vs_bind_app(cp, pd->pp);
         }
-        return dest;
+        rcu_read_unlock();
 }
 
 
diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index 2bfd807bc93f..0763cc6e092b 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -565,8 +565,8 @@ bool ip_vs_has_real_service(struct net *net, int af, __u16 protocol,
         return false;
 }
 
-/*
- *      Lookup destination by {addr,port} in the given service
+/* Lookup destination by {addr,port} in the given service
+ * Called under RCU lock.
  */
 static struct ip_vs_dest *
 ip_vs_lookup_dest(struct ip_vs_service *svc, const union nf_inet_addr *daddr,
@@ -577,7 +577,7 @@ ip_vs_lookup_dest(struct ip_vs_service *svc, const union nf_inet_addr *daddr,
         /*
          * Find the destination for the given service
          */
-        list_for_each_entry(dest, &svc->destinations, n_list) {
+        list_for_each_entry_rcu(dest, &svc->destinations, n_list) {
                 if ((dest->af == svc->af)
                     && ip_vs_addr_equal(svc->af, &dest->addr, daddr)
                     && (dest->port == dport)) {
@@ -591,10 +591,11 @@ ip_vs_lookup_dest(struct ip_vs_service *svc, const union nf_inet_addr *daddr,
 
 /*
  * Find destination by {daddr,dport,vaddr,protocol}
- * Cretaed to be used in ip_vs_process_message() in
+ * Created to be used in ip_vs_process_message() in
  * the backup synchronization daemon. It finds the
  * destination to be bound to the received connection
  * on the backup.
+ * Called under RCU lock, no refcnt is returned.
  */
 struct ip_vs_dest *ip_vs_find_dest(struct net  *net, int af,
                                    const union nf_inet_addr *daddr,
@@ -615,8 +616,6 @@ struct ip_vs_dest *ip_vs_find_dest(struct net  *net, int af,
         dest = ip_vs_lookup_dest(svc, daddr, port);
         if (!dest)
                 dest = ip_vs_lookup_dest(svc, daddr, port ^ dport);
-        if (dest)
-                ip_vs_dest_hold(dest);
         ip_vs_service_put(svc);
         return dest;
 }
@@ -826,7 +825,7 @@ __ip_vs_update_dest(struct ip_vs_service *svc, struct ip_vs_dest *dest,
         IP_VS_WAIT_WHILE(atomic_read(&svc->usecnt) > 0);
 
         if (add) {
-                list_add(&dest->n_list, &svc->destinations);
+                list_add_rcu(&dest->n_list, &svc->destinations);
                 svc->num_dests++;
                 if (svc->scheduler->add_dest)
                         svc->scheduler->add_dest(svc, dest);
@@ -933,10 +932,10 @@ ip_vs_add_dest(struct ip_vs_service *svc, struct ip_vs_dest_user_kern *udest)
 
         ip_vs_addr_copy(svc->af, &daddr, &udest->addr);
 
-        /*
-         * Check if the dest already exists in the list
-         */
+        /* We use function that requires RCU lock */
+        rcu_read_lock();
         dest = ip_vs_lookup_dest(svc, &daddr, dport);
+        rcu_read_unlock();
 
         if (dest != NULL) {
                 IP_VS_DBG(1, "%s(): dest already exists\n", __func__);
@@ -997,10 +996,10 @@ ip_vs_edit_dest(struct ip_vs_service *svc, struct ip_vs_dest_user_kern *udest)
 
         ip_vs_addr_copy(svc->af, &daddr, &udest->addr);
 
-        /*
-         *  Lookup the destination list
-         */
+        /* We use function that requires RCU lock */
+        rcu_read_lock();
         dest = ip_vs_lookup_dest(svc, &daddr, dport);
+        rcu_read_unlock();
 
         if (dest == NULL) {
                 IP_VS_DBG(1, "%s(): dest doesn't exist\n", __func__);
@@ -1069,7 +1068,7 @@ static void __ip_vs_unlink_dest(struct ip_vs_service *svc,
         /*
          *  Remove it from the d-linked destination list.
          */
-        list_del(&dest->n_list);
+        list_del_rcu(&dest->n_list);
         svc->num_dests--;
 
         if (svcupd && svc->scheduler->del_dest)
@@ -1094,7 +1093,10 @@ ip_vs_del_dest(struct ip_vs_service *svc, struct ip_vs_dest_user_kern *udest)
 
         EnterFunction(2);
 
+        /* We use function that requires RCU lock */
+        rcu_read_lock();
         dest = ip_vs_lookup_dest(svc, &udest->addr, dport);
+        rcu_read_unlock();
 
         if (dest == NULL) {
                 IP_VS_DBG(1, "%s(): destination not found!\n", __func__);
@@ -2104,7 +2106,7 @@ static int ip_vs_info_seq_show(struct seq_file *seq, void *v)
                 else
                         seq_putc(seq, '\n');
 
-                list_for_each_entry(dest, &svc->destinations, n_list) {
+                list_for_each_entry_rcu(dest, &svc->destinations, n_list) {
 #ifdef CONFIG_IP_VS_IPV6
                         if (dest->af == AF_INET6)
                                 seq_printf(seq,
diff --git a/net/netfilter/ipvs/ip_vs_sync.c b/net/netfilter/ipvs/ip_vs_sync.c
index 6cc3e52f1f35..97241749216d 100644
--- a/net/netfilter/ipvs/ip_vs_sync.c
+++ b/net/netfilter/ipvs/ip_vs_sync.c
@@ -858,23 +858,20 @@ static void ip_vs_proc_conn(struct net *net, struct ip_vs_conn_param *param,
                 flags |= cp->flags & ~IP_VS_CONN_F_BACKUP_UPD_MASK;
                 cp->flags = flags;
                 spin_unlock(&cp->lock);
-                if (!dest) {
-                        dest = ip_vs_try_bind_dest(cp);
-                        if (dest)
-                                ip_vs_dest_put(dest);
-                }
+                if (!dest)
+                        ip_vs_try_bind_dest(cp);
         } else {
                 /*
                  * Find the appropriate destination for the connection.
                  * If it is not found the connection will remain unbound
                  * but still handled.
                  */
+                rcu_read_lock();
                 dest = ip_vs_find_dest(net, type, daddr, dport, param->vaddr,
                                        param->vport, protocol, fwmark, flags);
 
                 cp = ip_vs_conn_new(param, daddr, dport, flags, dest, fwmark);
-                if (dest)
-                        ip_vs_dest_put(dest);
+                rcu_read_unlock();
                 if (!cp) {
                         if (param->pe_data)
                                 kfree(param->pe_data);