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;
 }