netfilter: nf_conntrack: use SLAB_DESTROY_BY_RCU and get rid of call_rcu()

Use "hlist_nulls" infrastructure we added in 2.6.29 for RCUification of UDP & TCP.

This permits an easy conversion from call_rcu() based hash lists to a
SLAB_DESTROY_BY_RCU one.

Avoiding call_rcu() delay at nf_conn freeing time has numerous gains.

First, it doesnt fill RCU queues (up to 10000 elements per cpu).
This reduces OOM possibility, if queued elements are not taken into account
This reduces latency problems when RCU queue size hits hilimit and triggers
emergency mode.

- It allows fast reuse of just freed elements, permitting better use of
CPU cache.

- We delete rcu_head from "struct nf_conn", shrinking size of this structure
by 8 or 16 bytes.

This patch only takes care of "struct nf_conn".
call_rcu() is still used for less critical conntrack parts, that may
be converted later if necessary.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 11 insertions, 9 deletions

diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 1b75c9efb0eb..349bbefe5517 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -19,6 +19,7 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/rculist.h>
+#include <linux/rculist_nulls.h>
 #include <linux/types.h>
 #include <linux/timer.h>
 #include <linux/skbuff.h>
@@ -536,7 +537,7 @@ ctnetlink_dump_table(struct sk_buff *skb, struct netlink_callback *cb)
 {
 	struct nf_conn *ct, *last;
 	struct nf_conntrack_tuple_hash *h;
-	struct hlist_node *n;
+	struct hlist_nulls_node *n;
 	struct nfgenmsg *nfmsg = NLMSG_DATA(cb->nlh);
 	u_int8_t l3proto = nfmsg->nfgen_family;
 
@@ -544,27 +545,27 @@ ctnetlink_dump_table(struct sk_buff *skb, struct netlink_callback *cb)
 	last = (struct nf_conn *)cb->args[1];
 	for (; cb->args[0] < nf_conntrack_htable_size; cb->args[0]++) {
 restart:
-		hlist_for_each_entry_rcu(h, n, &init_net.ct.hash[cb->args[0]],
-					 hnode) {
+		hlist_nulls_for_each_entry_rcu(h, n, &init_net.ct.hash[cb->args[0]],
+					 hnnode) {
 			if (NF_CT_DIRECTION(h) != IP_CT_DIR_ORIGINAL)
 				continue;
 			ct = nf_ct_tuplehash_to_ctrack(h);
+			if (!atomic_inc_not_zero(&ct->ct_general.use))
+				continue;
 			/* Dump entries of a given L3 protocol number.
 			 * If it is not specified, ie. l3proto == 0,
 			 * then dump everything. */
 			if (l3proto && nf_ct_l3num(ct) != l3proto)
-				continue;
+				goto releasect;
 			if (cb->args[1]) {
 				if (ct != last)
-					continue;
+					goto releasect;
 				cb->args[1] = 0;
 			}
 			if (ctnetlink_fill_info(skb, NETLINK_CB(cb->skb).pid,
 						cb->nlh->nlmsg_seq,
 						IPCTNL_MSG_CT_NEW,
 						1, ct) < 0) {
-				if (!atomic_inc_not_zero(&ct->ct_general.use))
-					continue;
 				cb->args[1] = (unsigned long)ct;
 				goto out;
 			}
@@ -577,6 +578,8 @@ restart:
 				if (acct)
 					memset(acct, 0, sizeof(struct nf_conn_counter[IP_CT_DIR_MAX]));
 			}
+releasect:
+		nf_ct_put(ct);
 		}
 		if (cb->args[1]) {
 			cb->args[1] = 0;
@@ -1242,13 +1245,12 @@ ctnetlink_create_conntrack(struct nlattr *cda[],
 		if (err < 0)
 			goto err2;
 
-		master_h = __nf_conntrack_find(&init_net, &master);
+		master_h = nf_conntrack_find_get(&init_net, &master);
 		if (master_h == NULL) {
 			err = -ENOENT;
 			goto err2;
 		}
 		master_ct = nf_ct_tuplehash_to_ctrack(master_h);
-		nf_conntrack_get(&master_ct->ct_general);
 		__set_bit(IPS_EXPECTED_BIT, &ct->status);
 		ct->master = master_ct;
 	}