[RFC PATCHv6 1/7] ipvs: add rcu protection to stats

[Julian Anastasov <ja@xxxxxx>]

In preparation to using RCU locking for the list
with estimators, make sure the struct ip_vs_stats
are released after RCU grace period by using RCU
callbacks. This affects ipvs->tot_stats where we
can not use RCU callbacks for ipvs, so we use
allocated struct ip_vs_stats_rcu. For services
and dests we force RCU callbacks for all cases.

Signed-off-by: Julian Anastasov <ja@xxxxxx>
---
 include/net/ip_vs.h             |  8 ++++-
 net/netfilter/ipvs/ip_vs_core.c | 10 ++++--
 net/netfilter/ipvs/ip_vs_ctl.c  | 64 ++++++++++++++++++++++-----------
 3 files changed, 57 insertions(+), 25 deletions(-)

diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
index ff1804a0c469..bd8ae137e43b 100644
--- a/include/net/ip_vs.h
+++ b/include/net/ip_vs.h
@@ -405,6 +405,11 @@ struct ip_vs_stats {
        struct ip_vs_kstats     kstats0;        /* reset values */
 };
 
+struct ip_vs_stats_rcu {
+       struct ip_vs_stats      s;
+       struct rcu_head         rcu_head;
+};
+
 struct dst_entry;
 struct iphdr;
 struct ip_vs_conn;
@@ -688,6 +693,7 @@ struct ip_vs_dest {
        union nf_inet_addr      vaddr;          /* virtual IP address */
        __u32                   vfwmark;        /* firewall mark of service */
 
+       struct rcu_head         rcu_head;
        struct list_head        t_list;         /* in dest_trash */
        unsigned int            in_rs_table:1;  /* we are in rs_table */
 };
@@ -869,7 +875,7 @@ struct netns_ipvs {
        atomic_t                conn_count;      /* connection counter */
 
        /* ip_vs_ctl */
-       struct ip_vs_stats              tot_stats;  /* Statistics & est. */
+       struct ip_vs_stats_rcu  *tot_stats;      /* Statistics & est. */
 
        int                     num_services;    /* no of virtual services */
        int                     num_services6;   /* IPv6 virtual services */
diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c
index 51ad557a525b..fcdaef1fcccf 100644
--- a/net/netfilter/ipvs/ip_vs_core.c
+++ b/net/netfilter/ipvs/ip_vs_core.c
@@ -143,7 +143,7 @@ ip_vs_in_stats(struct ip_vs_conn *cp, struct sk_buff *skb)
                s->cnt.inbytes += skb->len;
                u64_stats_update_end(&s->syncp);
 
-               s = this_cpu_ptr(ipvs->tot_stats.cpustats);
+               s = this_cpu_ptr(ipvs->tot_stats->s.cpustats);
                u64_stats_update_begin(&s->syncp);
                s->cnt.inpkts++;
                s->cnt.inbytes += skb->len;
@@ -179,7 +179,7 @@ ip_vs_out_stats(struct ip_vs_conn *cp, struct sk_buff *skb)
                s->cnt.outbytes += skb->len;
                u64_stats_update_end(&s->syncp);
 
-               s = this_cpu_ptr(ipvs->tot_stats.cpustats);
+               s = this_cpu_ptr(ipvs->tot_stats->s.cpustats);
                u64_stats_update_begin(&s->syncp);
                s->cnt.outpkts++;
                s->cnt.outbytes += skb->len;
@@ -208,7 +208,7 @@ ip_vs_conn_stats(struct ip_vs_conn *cp, struct 
ip_vs_service *svc)
        s->cnt.conns++;
        u64_stats_update_end(&s->syncp);
 
-       s = this_cpu_ptr(ipvs->tot_stats.cpustats);
+       s = this_cpu_ptr(ipvs->tot_stats->s.cpustats);
        u64_stats_update_begin(&s->syncp);
        s->cnt.conns++;
        u64_stats_update_end(&s->syncp);
@@ -2448,6 +2448,10 @@ static void __exit ip_vs_cleanup(void)
        ip_vs_conn_cleanup();
        ip_vs_protocol_cleanup();
        ip_vs_control_cleanup();
+       /* common rcu_barrier() used by:
+        * - ip_vs_control_cleanup()
+        */
+       rcu_barrier();
        pr_info("ipvs unloaded.\n");
 }
 
diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index 4d62059a6021..9016b641ae52 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -483,17 +483,14 @@ static void ip_vs_service_rcu_free(struct rcu_head *head)
        ip_vs_service_free(svc);
 }
 
-static void __ip_vs_svc_put(struct ip_vs_service *svc, bool do_delay)
+static void __ip_vs_svc_put(struct ip_vs_service *svc)
 {
        if (atomic_dec_and_test(&svc->refcnt)) {
                IP_VS_DBG_BUF(3, "Removing service %u/%s:%u\n",
                              svc->fwmark,
                              IP_VS_DBG_ADDR(svc->af, &svc->addr),
                              ntohs(svc->port));
-               if (do_delay)
-                       call_rcu(&svc->rcu_head, ip_vs_service_rcu_free);
-               else
-                       ip_vs_service_free(svc);
+               call_rcu(&svc->rcu_head, ip_vs_service_rcu_free);
        }
 }
 
@@ -780,14 +777,22 @@ ip_vs_trash_get_dest(struct ip_vs_service *svc, int 
dest_af,
        return dest;
 }
 
+static void ip_vs_dest_rcu_free(struct rcu_head *head)
+{
+       struct ip_vs_dest *dest;
+
+       dest = container_of(head, struct ip_vs_dest, rcu_head);
+       free_percpu(dest->stats.cpustats);
+       ip_vs_dest_put_and_free(dest);
+}
+
 static void ip_vs_dest_free(struct ip_vs_dest *dest)
 {
        struct ip_vs_service *svc = rcu_dereference_protected(dest->svc, 1);
 
        __ip_vs_dst_cache_reset(dest);
-       __ip_vs_svc_put(svc, false);
-       free_percpu(dest->stats.cpustats);
-       ip_vs_dest_put_and_free(dest);
+       __ip_vs_svc_put(svc);
+       call_rcu(&dest->rcu_head, ip_vs_dest_rcu_free);
 }
 
 /*
@@ -811,6 +816,16 @@ static void ip_vs_trash_cleanup(struct netns_ipvs *ipvs)
        }
 }
 
+static void ip_vs_stats_rcu_free(struct rcu_head *head)
+{
+       struct ip_vs_stats_rcu *rs = container_of(head,
+                                                 struct ip_vs_stats_rcu,
+                                                 rcu_head);
+
+       free_percpu(rs->s.cpustats);
+       kfree(rs);
+}
+
 static void
 ip_vs_copy_stats(struct ip_vs_kstats *dst, struct ip_vs_stats *src)
 {
@@ -923,7 +938,7 @@ __ip_vs_update_dest(struct ip_vs_service *svc, struct 
ip_vs_dest *dest,
                if (old_svc != svc) {
                        ip_vs_zero_stats(&dest->stats);
                        __ip_vs_bind_svc(dest, svc);
-                       __ip_vs_svc_put(old_svc, true);
+                       __ip_vs_svc_put(old_svc);
                }
        }
 
@@ -1571,7 +1586,7 @@ static void __ip_vs_del_service(struct ip_vs_service 
*svc, bool cleanup)
        /*
         *    Free the service if nobody refers to it
         */
-       __ip_vs_svc_put(svc, true);
+       __ip_vs_svc_put(svc);
 
        /* decrease the module use count */
        ip_vs_use_count_dec();
@@ -1761,7 +1776,7 @@ static int ip_vs_zero_all(struct netns_ipvs *ipvs)
                }
        }
 
-       ip_vs_zero_stats(&ipvs->tot_stats);
+       ip_vs_zero_stats(&ipvs->tot_stats->s);
        return 0;
 }
 
@@ -2255,7 +2270,7 @@ static int ip_vs_stats_show(struct seq_file *seq, void *v)
        seq_puts(seq,
                 "   Conns  Packets  Packets            Bytes            
Bytes\n");
 
-       ip_vs_copy_stats(&show, &net_ipvs(net)->tot_stats);
+       ip_vs_copy_stats(&show, &net_ipvs(net)->tot_stats->s);
        seq_printf(seq, "%8LX %8LX %8LX %16LX %16LX\n\n",
                   (unsigned long long)show.conns,
                   (unsigned long long)show.inpkts,
@@ -2279,7 +2294,7 @@ static int ip_vs_stats_show(struct seq_file *seq, void *v)
 static int ip_vs_stats_percpu_show(struct seq_file *seq, void *v)
 {
        struct net *net = seq_file_single_net(seq);
-       struct ip_vs_stats *tot_stats = &net_ipvs(net)->tot_stats;
+       struct ip_vs_stats *tot_stats = &net_ipvs(net)->tot_stats->s;
        struct ip_vs_cpu_stats __percpu *cpustats = tot_stats->cpustats;
        struct ip_vs_kstats kstats;
        int i;
@@ -4107,7 +4122,6 @@ static int __net_init 
ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
                        kfree(tbl);
                return -ENOMEM;
        }
-       ip_vs_start_estimator(ipvs, &ipvs->tot_stats);
        ipvs->sysctl_tbl = tbl;
        /* Schedule defense work */
        INIT_DELAYED_WORK(&ipvs->defense_work, defense_work_handler);
@@ -4118,6 +4132,7 @@ static int __net_init 
ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
        INIT_DELAYED_WORK(&ipvs->expire_nodest_conn_work,
                          expire_nodest_conn_handler);
 
+       ip_vs_start_estimator(ipvs, &ipvs->tot_stats->s);
        return 0;
 }
 
@@ -4129,7 +4144,7 @@ static void __net_exit 
ip_vs_control_net_cleanup_sysctl(struct netns_ipvs *ipvs)
        cancel_delayed_work_sync(&ipvs->defense_work);
        cancel_work_sync(&ipvs->defense_work.work);
        unregister_net_sysctl_table(ipvs->sysctl_hdr);
-       ip_vs_stop_estimator(ipvs, &ipvs->tot_stats);
+       ip_vs_stop_estimator(ipvs, &ipvs->tot_stats->s);
 
        if (!net_eq(net, &init_net))
                kfree(ipvs->sysctl_tbl);
@@ -4165,17 +4180,20 @@ int __net_init ip_vs_control_net_init(struct netns_ipvs 
*ipvs)
        atomic_set(&ipvs->conn_out_counter, 0);
 
        /* procfs stats */
-       ipvs->tot_stats.cpustats = alloc_percpu(struct ip_vs_cpu_stats);
-       if (!ipvs->tot_stats.cpustats)
+       ipvs->tot_stats = kzalloc(sizeof(*ipvs->tot_stats), GFP_KERNEL);
+       if (!ipvs->tot_stats)
                return -ENOMEM;
+       ipvs->tot_stats->s.cpustats = alloc_percpu(struct ip_vs_cpu_stats);
+       if (!ipvs->tot_stats->s.cpustats)
+               goto err_tot_stats;
 
        for_each_possible_cpu(i) {
                struct ip_vs_cpu_stats *ipvs_tot_stats;
-               ipvs_tot_stats = per_cpu_ptr(ipvs->tot_stats.cpustats, i);
+               ipvs_tot_stats = per_cpu_ptr(ipvs->tot_stats->s.cpustats, i);
                u64_stats_init(&ipvs_tot_stats->syncp);
        }
 
-       spin_lock_init(&ipvs->tot_stats.lock);
+       spin_lock_init(&ipvs->tot_stats->s.lock);
 
 #ifdef CONFIG_PROC_FS
        if (!proc_create_net("ip_vs", 0, ipvs->net->proc_net,
@@ -4207,7 +4225,10 @@ int __net_init ip_vs_control_net_init(struct netns_ipvs 
*ipvs)
 
 err_vs:
 #endif
-       free_percpu(ipvs->tot_stats.cpustats);
+       free_percpu(ipvs->tot_stats->s.cpustats);
+
+err_tot_stats:
+       kfree(ipvs->tot_stats);
        return -ENOMEM;
 }
 
@@ -4220,7 +4241,7 @@ void __net_exit ip_vs_control_net_cleanup(struct 
netns_ipvs *ipvs)
        remove_proc_entry("ip_vs_stats", ipvs->net->proc_net);
        remove_proc_entry("ip_vs", ipvs->net->proc_net);
 #endif
-       free_percpu(ipvs->tot_stats.cpustats);
+       call_rcu(&ipvs->tot_stats->rcu_head, ip_vs_stats_rcu_free);
 }
 
 int __init ip_vs_register_nl_ioctl(void)
@@ -4280,5 +4301,6 @@ void ip_vs_control_cleanup(void)
 {
        EnterFunction(2);
        unregister_netdevice_notifier(&ip_vs_dst_notifier);
+       /* relying on common rcu_barrier() in ip_vs_cleanup() */
        LeaveFunction(2);
 }
-- 
2.38.1