fib: RCU conversion of fib_lookup()

fib_lookup() converted to be called in RCU protected context, no
reference taken and released on a contended cache line (fib_clntref)

fib_table_lookup() and fib_semantic_match() get an additional parameter.

struct fib_info gets an rcu_head field, and is freed after an rcu grace
period.

Stress test :
(Sending 160.000.000 UDP frames on same neighbour,
IP route cache disabled, dual E5540 @2.53GHz,
32bit kernel, FIB_HASH) (about same results for FIB_TRIE)

Before patch :

real	1m31.199s
user	0m13.761s
sys	23m24.780s

After patch:

real	1m5.375s
user	0m14.997s
sys	15m50.115s

Before patch Profile :

13044.00 15.4% __ip_route_output_key vmlinux
 8438.00 10.0% dst_destroy           vmlinux
 5983.00  7.1% fib_semantic_match    vmlinux
 5410.00  6.4% fib_rules_lookup      vmlinux
 4803.00  5.7% neigh_lookup          vmlinux
 4420.00  5.2% _raw_spin_lock        vmlinux
 3883.00  4.6% rt_set_nexthop        vmlinux
 3261.00  3.9% _raw_read_lock        vmlinux
 2794.00  3.3% fib_table_lookup      vmlinux
 2374.00  2.8% neigh_resolve_output  vmlinux
 2153.00  2.5% dst_alloc             vmlinux
 1502.00  1.8% _raw_read_lock_bh     vmlinux
 1484.00  1.8% kmem_cache_alloc      vmlinux
 1407.00  1.7% eth_header            vmlinux
 1406.00  1.7% ipv4_dst_destroy      vmlinux
 1298.00  1.5% __copy_from_user_ll   vmlinux
 1174.00  1.4% dev_queue_xmit        vmlinux
 1000.00  1.2% ip_output             vmlinux

After patch Profile :

13712.00 15.8% dst_destroy             vmlinux
 8548.00  9.9% __ip_route_output_key   vmlinux
 7017.00  8.1% neigh_lookup            vmlinux
 4554.00  5.3% fib_semantic_match      vmlinux
 4067.00  4.7% _raw_read_lock          vmlinux
 3491.00  4.0% dst_alloc               vmlinux
 3186.00  3.7% neigh_resolve_output    vmlinux
 3103.00  3.6% fib_table_lookup        vmlinux
 2098.00  2.4% _raw_read_lock_bh       vmlinux
 2081.00  2.4% kmem_cache_alloc        vmlinux
 2013.00  2.3% _raw_spin_lock          vmlinux
 1763.00  2.0% __copy_from_user_ll     vmlinux
 1763.00  2.0% ip_output               vmlinux
 1761.00  2.0% ipv4_dst_destroy        vmlinux
 1631.00  1.9% eth_header              vmlinux
 1440.00  1.7% _raw_read_unlock_bh     vmlinux

Reference results, if IP route cache is enabled :

real	0m29.718s
user	0m10.845s
sys	7m37.341s

25213.00 29.5% __ip_route_output_key   vmlinux
 9011.00 10.5% dst_release             vmlinux
 4817.00  5.6% ip_push_pending_frames  vmlinux
 4232.00  5.0% ip_finish_output        vmlinux
 3940.00  4.6% udp_sendmsg             vmlinux
 3730.00  4.4% __copy_from_user_ll     vmlinux
 3716.00  4.4% ip_route_output_flow    vmlinux
 2451.00  2.9% __xfrm_lookup           vmlinux
 2221.00  2.6% ip_append_data          vmlinux
 1718.00  2.0% _raw_spin_lock_bh       vmlinux
 1655.00  1.9% __alloc_skb             vmlinux
 1572.00  1.8% sock_wfree              vmlinux
 1345.00  1.6% kfree                   vmlinux

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 24 insertions, 35 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 04e0df82b88c..7864d0c48968 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1773,12 +1773,15 @@ void ip_rt_get_source(u8 *addr, struct rtable *rt)
 
 	if (rt->fl.iif == 0)
 		src = rt->rt_src;
-	else if (fib_lookup(dev_net(rt->dst.dev), &rt->fl, &res) == 0) {
-		src = FIB_RES_PREFSRC(res);
-		fib_res_put(&res);
-	} else
-		src = inet_select_addr(rt->dst.dev, rt->rt_gateway,
+	else {
+		rcu_read_lock();
+		if (fib_lookup(dev_net(rt->dst.dev), &rt->fl, &res) == 0)
+			src = FIB_RES_PREFSRC(res);
+		else
+			src = inet_select_addr(rt->dst.dev, rt->rt_gateway,
 					RT_SCOPE_UNIVERSE);
+		rcu_read_unlock();
+	}
 	memcpy(addr, &src, 4);
 }
 
@@ -2081,6 +2084,7 @@ static int ip_mkroute_input(struct sk_buff *skb,
  *	Such approach solves two big problems:
  *	1. Not simplex devices are handled properly.
  *	2. IP spoofing attempts are filtered with 100% of guarantee.
+ *	called with rcu_read_lock()
  */
 
 static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
@@ -2102,7 +2106,6 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 	unsigned	hash;
 	__be32		spec_dst;
 	int		err = -EINVAL;
-	int		free_res = 0;
 	struct net    * net = dev_net(dev);
 
 	/* IP on this device is disabled. */
@@ -2134,12 +2137,12 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 	/*
 	 *	Now we are ready to route packet.
 	 */
-	if ((err = fib_lookup(net, &fl, &res)) != 0) {
+	err = fib_lookup(net, &fl, &res);
+	if (err != 0) {
 		if (!IN_DEV_FORWARD(in_dev))
 			goto e_hostunreach;
 		goto no_route;
 	}
-	free_res = 1;
 
 	RT_CACHE_STAT_INC(in_slow_tot);
 
@@ -2148,8 +2151,8 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 
 	if (res.type == RTN_LOCAL) {
 		err = fib_validate_source(saddr, daddr, tos,
-					     net->loopback_dev->ifindex,
-					     dev, &spec_dst, &itag, skb->mark);
+					  net->loopback_dev->ifindex,
+					  dev, &spec_dst, &itag, skb->mark);
 		if (err < 0)
 			goto martian_source_keep_err;
 		if (err)
@@ -2164,9 +2167,6 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 		goto martian_destination;
 
 	err = ip_mkroute_input(skb, &res, &fl, in_dev, daddr, saddr, tos);
-done:
-	if (free_res)
-		fib_res_put(&res);
 out:	return err;
 
 brd_input:
@@ -2226,7 +2226,7 @@ local_input:
 	rth->rt_type	= res.type;
 	hash = rt_hash(daddr, saddr, fl.iif, rt_genid(net));
 	err = rt_intern_hash(hash, rth, NULL, skb, fl.iif);
-	goto done;
+	goto out;
 
 no_route:
 	RT_CACHE_STAT_INC(in_no_route);
@@ -2249,21 +2249,21 @@ martian_destination:
 
 e_hostunreach:
 	err = -EHOSTUNREACH;
-	goto done;
+	goto out;
 
 e_inval:
 	err = -EINVAL;
-	goto done;
+	goto out;
 
 e_nobufs:
 	err = -ENOBUFS;
-	goto done;
+	goto out;
 
 martian_source:
 	err = -EINVAL;
 martian_source_keep_err:
 	ip_handle_martian_source(dev, in_dev, skb, daddr, saddr);
-	goto done;
+	goto out;
 }
 
 int ip_route_input_common(struct sk_buff *skb, __be32 daddr, __be32 saddr,
@@ -2349,6 +2349,7 @@ skip_cache:
 }
 EXPORT_SYMBOL(ip_route_input_common);
 
+/* called with rcu_read_lock() */
 static int __mkroute_output(struct rtable **result,
 			    struct fib_result *res,
 			    const struct flowi *fl,
@@ -2373,18 +2374,13 @@ static int __mkroute_output(struct rtable **result,
 	if (dev_out->flags & IFF_LOOPBACK)
 		flags |= RTCF_LOCAL;
 
-	rcu_read_lock();
 	in_dev = __in_dev_get_rcu(dev_out);
-	if (!in_dev) {
-		rcu_read_unlock();
+	if (!in_dev)
 		return -EINVAL;
-	}
+
 	if (res->type == RTN_BROADCAST) {
 		flags |= RTCF_BROADCAST | RTCF_LOCAL;
-		if (res->fi) {
-			fib_info_put(res->fi);
-			res->fi = NULL;
-		}
+		res->fi = NULL;
 	} else if (res->type == RTN_MULTICAST) {
 		flags |= RTCF_MULTICAST | RTCF_LOCAL;
 		if (!ip_check_mc(in_dev, oldflp->fl4_dst, oldflp->fl4_src,
@@ -2394,10 +2390,8 @@ static int __mkroute_output(struct rtable **result,
 		 * default one, but do not gateway in this case.
 		 * Yes, it is hack.
 		 */
-		if (res->fi && res->prefixlen < 4) {
-			fib_info_put(res->fi);
+		if (res->fi && res->prefixlen < 4)
 			res->fi = NULL;
-		}
 	}
 
 
@@ -2467,6 +2461,7 @@ static int __mkroute_output(struct rtable **result,
 	return 0;
 }
 
+/* called with rcu_read_lock() */
 static int ip_mkroute_output(struct rtable **rp,
 			     struct fib_result *res,
 			     const struct flowi *fl,
@@ -2509,7 +2504,6 @@ static int ip_route_output_slow(struct net *net, struct rtable **rp,
 	struct fib_result res;
 	unsigned int flags = 0;
 	struct net_device *dev_out = NULL;
-	int free_res = 0;
 	int err;
 
 
@@ -2636,15 +2630,12 @@ static int ip_route_output_slow(struct net *net, struct rtable **rp,
 		err = -ENETUNREACH;
 		goto out;
 	}
-	free_res = 1;
 
 	if (res.type == RTN_LOCAL) {
 		if (!fl.fl4_src)
 			fl.fl4_src = fl.fl4_dst;
 		dev_out = net->loopback_dev;
 		fl.oif = dev_out->ifindex;
-		if (res.fi)
-			fib_info_put(res.fi);
 		res.fi = NULL;
 		flags |= RTCF_LOCAL;
 		goto make_route;
@@ -2668,8 +2659,6 @@ static int ip_route_output_slow(struct net *net, struct rtable **rp,
 make_route:
 	err = ip_mkroute_output(rp, &res, &fl, oldflp, dev_out, flags);
 
-	if (free_res)
-		fib_res_put(&res);
 out:	return err;
 }