[NETFILTER]: nf_conntrack_expect: use RCU for expectation hash

Use RCU for expectation hash. This doesn't buy much for conntrack
runtime performance, but allows to reduce the use of nf_conntrack_lock
for /proc and nf_netlink_conntrack.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 31 insertions, 19 deletions

diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c
index e405079e5a49..a5c8ef01f925 100644
--- a/net/netfilter/nf_conntrack_expect.c
+++ b/net/netfilter/nf_conntrack_expect.c
@@ -50,7 +50,7 @@ void nf_ct_unlink_expect(struct nf_conntrack_expect *exp)
         NF_CT_ASSERT(master_help);
         NF_CT_ASSERT(!timer_pending(&exp->timeout));
 
-        hlist_del(&exp->hnode);
+        hlist_del_rcu(&exp->hnode);
         nf_ct_expect_count--;
 
         hlist_del(&exp->lnode);
@@ -97,7 +97,7 @@ __nf_ct_expect_find(const struct nf_conntrack_tuple *tuple)
                 return NULL;
 
         h = nf_ct_expect_dst_hash(tuple);
-        hlist_for_each_entry(i, n, &nf_ct_expect_hash[h], hnode) {
+        hlist_for_each_entry_rcu(i, n, &nf_ct_expect_hash[h], hnode) {
                 if (nf_ct_tuple_mask_cmp(tuple, &i->tuple, &i->mask))
                         return i;
         }
@@ -111,11 +111,11 @@ nf_ct_expect_find_get(const struct nf_conntrack_tuple *tuple)
 {
         struct nf_conntrack_expect *i;
 
-        read_lock_bh(&nf_conntrack_lock);
+        rcu_read_lock();
         i = __nf_ct_expect_find(tuple);
-        if (i)
-                atomic_inc(&i->use);
-        read_unlock_bh(&nf_conntrack_lock);
+        if (i && !atomic_inc_not_zero(&i->use))
+                i = NULL;
+        rcu_read_unlock();
 
         return i;
 }
@@ -223,6 +223,7 @@ struct nf_conntrack_expect *nf_ct_expect_alloc(struct nf_conn *me)
 
         new->master = me;
         atomic_set(&new->use, 1);
+        INIT_RCU_HEAD(&new->rcu);
         return new;
 }
 EXPORT_SYMBOL_GPL(nf_ct_expect_alloc);
@@ -278,10 +279,18 @@ void nf_ct_expect_init(struct nf_conntrack_expect *exp, int family,
 }
 EXPORT_SYMBOL_GPL(nf_ct_expect_init);
 
+static void nf_ct_expect_free_rcu(struct rcu_head *head)
+{
+        struct nf_conntrack_expect *exp;
+
+        exp = container_of(head, struct nf_conntrack_expect, rcu);
+        kmem_cache_free(nf_ct_expect_cachep, exp);
+}
+
 void nf_ct_expect_put(struct nf_conntrack_expect *exp)
 {
         if (atomic_dec_and_test(&exp->use))
-                kmem_cache_free(nf_ct_expect_cachep, exp);
+                call_rcu(&exp->rcu, nf_ct_expect_free_rcu);
 }
 EXPORT_SYMBOL_GPL(nf_ct_expect_put);
 
@@ -295,7 +304,7 @@ static void nf_ct_expect_insert(struct nf_conntrack_expect *exp)
         hlist_add_head(&exp->lnode, &master_help->expectations);
         master_help->expecting++;
 
-        hlist_add_head(&exp->hnode, &nf_ct_expect_hash[h]);
+        hlist_add_head_rcu(&exp->hnode, &nf_ct_expect_hash[h]);
         nf_ct_expect_count++;
 
         setup_timer(&exp->timeout, nf_ct_expectation_timed_out,
@@ -394,10 +403,12 @@ struct ct_expect_iter_state {
 static struct hlist_node *ct_expect_get_first(struct seq_file *seq)
 {
         struct ct_expect_iter_state *st = seq->private;
+        struct hlist_node *n;
 
         for (st->bucket = 0; st->bucket < nf_ct_expect_hsize; st->bucket++) {
-                if (!hlist_empty(&nf_ct_expect_hash[st->bucket]))
-                        return nf_ct_expect_hash[st->bucket].first;
+                n = rcu_dereference(nf_ct_expect_hash[st->bucket].first);
+                if (n)
+                        return n;
         }
         return NULL;
 }
@@ -407,11 +418,11 @@ static struct hlist_node *ct_expect_get_next(struct seq_file *seq,
 {
         struct ct_expect_iter_state *st = seq->private;
 
-        head = head->next;
+        head = rcu_dereference(head->next);
         while (head == NULL) {
                 if (++st->bucket >= nf_ct_expect_hsize)
                         return NULL;
-                head = nf_ct_expect_hash[st->bucket].first;
+                head = rcu_dereference(nf_ct_expect_hash[st->bucket].first);
         }
         return head;
 }
@@ -427,9 +438,9 @@ static struct hlist_node *ct_expect_get_idx(struct seq_file *seq, loff_t pos)
 }
 
 static void *exp_seq_start(struct seq_file *seq, loff_t *pos)
-        __acquires(nf_conntrack_lock)
+        __acquires(RCU)
 {
-        read_lock_bh(&nf_conntrack_lock);
+        rcu_read_lock();
         return ct_expect_get_idx(seq, *pos);
 }
 
@@ -440,9 +451,9 @@ static void *exp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 }
 
 static void exp_seq_stop(struct seq_file *seq, void *v)
-        __releases(nf_conntrack_lock)
+        __releases(RCU)
 {
-        read_unlock_bh(&nf_conntrack_lock);
+        rcu_read_unlock();
 }
 
 static int exp_seq_show(struct seq_file *s, void *v)
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index b6c0935e09df..557f47137da0 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -1471,7 +1471,7 @@ ctnetlink_exp_dump_table(struct sk_buff *skb, struct netlink_callback *cb)
         struct hlist_node *n;
         u_int8_t l3proto = nfmsg->nfgen_family;
 
-        read_lock_bh(&nf_conntrack_lock);
+        rcu_read_lock();
         last = (struct nf_conntrack_expect *)cb->args[1];
         for (; cb->args[0] < nf_ct_expect_hsize; cb->args[0]++) {
 restart:
@@ -1488,7 +1488,8 @@ restart:
                                                     cb->nlh->nlmsg_seq,
                                                     IPCTNL_MSG_EXP_NEW,
                                                     1, exp) < 0) {
-                                atomic_inc(&exp->use);
+                                if (!atomic_inc_not_zero(&exp->use))
+                                        continue;
                                 cb->args[1] = (unsigned long)exp;
                                 goto out;
                         }
@@ -1499,7 +1500,7 @@ restart:
                 }
         }
 out:
-        read_unlock_bh(&nf_conntrack_lock);
+        rcu_read_unlock();
         if (last)
                 nf_ct_expect_put(last);