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>

8 files changed, 66 insertions, 64 deletions

diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index cfb7d25c172d..21698f8c49ee 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -225,7 +225,8 @@ jumped:
                         err = ops->action(rule, fl, flags, arg);
 
                 if (err != -EAGAIN) {
-                        if (likely(atomic_inc_not_zero(&rule->refcnt))) {
+                        if ((arg->flags & FIB_LOOKUP_NOREF) ||
+                            likely(atomic_inc_not_zero(&rule->refcnt))) {
                                 arg->rule = rule;
                                 goto out;
                         }
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index b05c23b05a9f..919f2ad19b49 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -168,8 +168,11 @@ struct net_device *__ip_dev_find(struct net *net, __be32 addr, bool devref)
         struct fib_result res = { 0 };
         struct net_device *dev = NULL;
 
-        if (fib_lookup(net, &fl, &res))
+        rcu_read_lock();
+        if (fib_lookup(net, &fl, &res)) {
+                rcu_read_unlock();
                 return NULL;
+        }
         if (res.type != RTN_LOCAL)
                 goto out;
         dev = FIB_RES_DEV(res);
@@ -177,7 +180,7 @@ struct net_device *__ip_dev_find(struct net *net, __be32 addr, bool devref)
         if (dev && devref)
                 dev_hold(dev);
 out:
-        fib_res_put(&res);
+        rcu_read_unlock();
         return dev;
 }
 EXPORT_SYMBOL(__ip_dev_find);
@@ -207,11 +210,12 @@ static inline unsigned __inet_dev_addr_type(struct net *net,
         local_table = fib_get_table(net, RT_TABLE_LOCAL);
         if (local_table) {
                 ret = RTN_UNICAST;
-                if (!fib_table_lookup(local_table, &fl, &res)) {
+                rcu_read_lock();
+                if (!fib_table_lookup(local_table, &fl, &res, FIB_LOOKUP_NOREF)) {
                         if (!dev || dev == res.fi->fib_dev)
                                 ret = res.type;
-                        fib_res_put(&res);
                 }
+                rcu_read_unlock();
         }
         return ret;
 }
@@ -235,6 +239,7 @@ EXPORT_SYMBOL(inet_dev_addr_type);
  * - figure out what "logical" interface this packet arrived
  *   and calculate "specific destination" address.
  * - check, that packet arrived from expected physical interface.
+ * called with rcu_read_lock()
  */
 int fib_validate_source(__be32 src, __be32 dst, u8 tos, int oif,
                         struct net_device *dev, __be32 *spec_dst,
@@ -259,7 +264,6 @@ int fib_validate_source(__be32 src, __be32 dst, u8 tos, int oif,
         struct net *net;
 
         no_addr = rpf = accept_local = 0;
-        rcu_read_lock();
         in_dev = __in_dev_get_rcu(dev);
         if (in_dev) {
                 no_addr = in_dev->ifa_list == NULL;
@@ -268,7 +272,6 @@ int fib_validate_source(__be32 src, __be32 dst, u8 tos, int oif,
                 if (mark && !IN_DEV_SRC_VMARK(in_dev))
                         fl.mark = 0;
         }
-        rcu_read_unlock();
 
         if (in_dev == NULL)
                 goto e_inval;
@@ -278,7 +281,7 @@ int fib_validate_source(__be32 src, __be32 dst, u8 tos, int oif,
                 goto last_resort;
         if (res.type != RTN_UNICAST) {
                 if (res.type != RTN_LOCAL || !accept_local)
-                        goto e_inval_res;
+                        goto e_inval;
         }
         *spec_dst = FIB_RES_PREFSRC(res);
         fib_combine_itag(itag, &res);
@@ -299,10 +302,8 @@ int fib_validate_source(__be32 src, __be32 dst, u8 tos, int oif,
 #endif
         if (dev_match) {
                 ret = FIB_RES_NH(res).nh_scope >= RT_SCOPE_HOST;
-                fib_res_put(&res);
                 return ret;
         }
-        fib_res_put(&res);
         if (no_addr)
                 goto last_resort;
         if (rpf == 1)
@@ -315,7 +316,6 @@ int fib_validate_source(__be32 src, __be32 dst, u8 tos, int oif,
                         *spec_dst = FIB_RES_PREFSRC(res);
                         ret = FIB_RES_NH(res).nh_scope >= RT_SCOPE_HOST;
                 }
-                fib_res_put(&res);
         }
         return ret;
 
@@ -326,8 +326,6 @@ last_resort:
         *itag = 0;
         return 0;
 
-e_inval_res:
-        fib_res_put(&res);
 e_inval:
         return -EINVAL;
 e_rpf:
@@ -873,15 +871,16 @@ static void nl_fib_lookup(struct fib_result_nl *frn, struct fib_table *tb)
                 local_bh_disable();
 
                 frn->tb_id = tb->tb_id;
-                frn->err = fib_table_lookup(tb, &fl, &res);
+                rcu_read_lock();
+                frn->err = fib_table_lookup(tb, &fl, &res, FIB_LOOKUP_NOREF);
 
                 if (!frn->err) {
                         frn->prefixlen = res.prefixlen;
                         frn->nh_sel = res.nh_sel;
                         frn->type = res.type;
                         frn->scope = res.scope;
-                        fib_res_put(&res);
                 }
+                rcu_read_unlock();
                 local_bh_enable();
         }
 }
diff --git a/net/ipv4/fib_hash.c b/net/ipv4/fib_hash.c
index 4ed7e0dea1bc..83cca68e259c 100644
--- a/net/ipv4/fib_hash.c
+++ b/net/ipv4/fib_hash.c
@@ -244,7 +244,8 @@ fn_new_zone(struct fn_hash *table, int z)
 }
 
 int fib_table_lookup(struct fib_table *tb,
-                     const struct flowi *flp, struct fib_result *res)
+                     const struct flowi *flp, struct fib_result *res,
+                     int fib_flags)
 {
         int err;
         struct fn_zone *fz;
@@ -264,7 +265,7 @@ int fib_table_lookup(struct fib_table *tb,
 
                         err = fib_semantic_match(&f->fn_alias,
                                                  flp, res,
-                                                 fz->fz_order);
+                                                 fz->fz_order, fib_flags);
                         if (err <= 0)
                                 goto out;
                 }
diff --git a/net/ipv4/fib_lookup.h b/net/ipv4/fib_lookup.h
index 637b133973bd..b9c9a9f2aee5 100644
--- a/net/ipv4/fib_lookup.h
+++ b/net/ipv4/fib_lookup.h
@@ -22,7 +22,7 @@ struct fib_alias {
 /* Exported by fib_semantics.c */
 extern int fib_semantic_match(struct list_head *head,
                               const struct flowi *flp,
-                              struct fib_result *res, int prefixlen);
+                              struct fib_result *res, int prefixlen, int fib_flags);
 extern void fib_release_info(struct fib_info *);
 extern struct fib_info *fib_create_info(struct fib_config *cfg);
 extern int fib_nh_match(struct fib_config *cfg, struct fib_info *fi);
diff --git a/net/ipv4/fib_rules.c b/net/ipv4/fib_rules.c
index 32300521e32c..7981a24f5c7b 100644
--- a/net/ipv4/fib_rules.c
+++ b/net/ipv4/fib_rules.c
@@ -57,6 +57,7 @@ int fib_lookup(struct net *net, struct flowi *flp, struct fib_result *res)
 {
         struct fib_lookup_arg arg = {
                 .result = res,
+                .flags = FIB_LOOKUP_NOREF,
         };
         int err;
 
@@ -94,7 +95,7 @@ static int fib4_rule_action(struct fib_rule *rule, struct flowi *flp,
         if (!tbl)
                 goto errout;
 
-        err = fib_table_lookup(tbl, flp, (struct fib_result *) arg->result);
+        err = fib_table_lookup(tbl, flp, (struct fib_result *) arg->result, arg->flags);
         if (err > 0)
                 err = -EAGAIN;
 errout:
diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index ba52f399a898..0f80dfc2f7fb 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -148,6 +148,13 @@ static const struct
 
 /* Release a nexthop info record */
 
+static void free_fib_info_rcu(struct rcu_head *head)
+{
+        struct fib_info *fi = container_of(head, struct fib_info, rcu);
+
+        kfree(fi);
+}
+
 void free_fib_info(struct fib_info *fi)
 {
         if (fi->fib_dead == 0) {
@@ -161,7 +168,7 @@ void free_fib_info(struct fib_info *fi)
         } endfor_nexthops(fi);
         fib_info_cnt--;
         release_net(fi->fib_net);
-        kfree(fi);
+        call_rcu(&fi->rcu, free_fib_info_rcu);
 }
 
 void fib_release_info(struct fib_info *fi)
@@ -553,6 +560,7 @@ static int fib_check_nh(struct fib_config *cfg, struct fib_info *fi,
                         nh->nh_scope = RT_SCOPE_LINK;
                         return 0;
                 }
+                rcu_read_lock();
                 {
                         struct flowi fl = {
                                 .nl_u = {
@@ -568,8 +576,10 @@ static int fib_check_nh(struct fib_config *cfg, struct fib_info *fi,
                         if (fl.fl4_scope < RT_SCOPE_LINK)
                                 fl.fl4_scope = RT_SCOPE_LINK;
                         err = fib_lookup(net, &fl, &res);
-                        if (err)
+                        if (err) {
+                                rcu_read_unlock();
                                 return err;
+                        }
                 }
                 err = -EINVAL;
                 if (res.type != RTN_UNICAST && res.type != RTN_LOCAL)
@@ -585,7 +595,7 @@ static int fib_check_nh(struct fib_config *cfg, struct fib_info *fi,
                         goto out;
                 err = 0;
 out:
-                fib_res_put(&res);
+                rcu_read_unlock();
                 return err;
         } else {
                 struct in_device *in_dev;
@@ -879,7 +889,7 @@ failure:
 
 /* Note! fib_semantic_match intentionally uses  RCU list functions. */
 int fib_semantic_match(struct list_head *head, const struct flowi *flp,
-                       struct fib_result *res, int prefixlen)
+                       struct fib_result *res, int prefixlen, int fib_flags)
 {
         struct fib_alias *fa;
         int nh_sel = 0;
@@ -943,7 +953,8 @@ out_fill_res:
         res->type = fa->fa_type;
         res->scope = fa->fa_scope;
         res->fi = fa->fa_info;
-        atomic_inc(&res->fi->fib_clntref);
+        if (!(fib_flags & FIB_LOOKUP_NOREF))
+                atomic_inc(&res->fi->fib_clntref);
         return 0;
 }
 
diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index a96e5ec211a0..271c89bdf049 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -1342,7 +1342,7 @@ err:
 /* should be called with rcu_read_lock */
 static int check_leaf(struct trie *t, struct leaf *l,
                       t_key key,  const struct flowi *flp,
-                      struct fib_result *res)
+                      struct fib_result *res, int fib_flags)
 {
         struct leaf_info *li;
         struct hlist_head *hhead = &l->list;
@@ -1356,7 +1356,7 @@ static int check_leaf(struct trie *t, struct leaf *l,
                 if (l->key != (key & ntohl(mask)))
                         continue;
 
-                err = fib_semantic_match(&li->falh, flp, res, plen);
+                err = fib_semantic_match(&li->falh, flp, res, plen, fib_flags);
 
 #ifdef CONFIG_IP_FIB_TRIE_STATS
                 if (err <= 0)
@@ -1372,7 +1372,7 @@ static int check_leaf(struct trie *t, struct leaf *l,
 }
 
 int fib_table_lookup(struct fib_table *tb, const struct flowi *flp,
-                     struct fib_result *res)
+                     struct fib_result *res, int fib_flags)
 {
         struct trie *t = (struct trie *) tb->tb_data;
         int ret;
@@ -1399,7 +1399,7 @@ int fib_table_lookup(struct fib_table *tb, const struct flowi *flp,
 
         /* Just a leaf? */
         if (IS_LEAF(n)) {
-                ret = check_leaf(t, (struct leaf *)n, key, flp, res);
+                ret = check_leaf(t, (struct leaf *)n, key, flp, res, fib_flags);
                 goto found;
         }
 
@@ -1424,7 +1424,7 @@ int fib_table_lookup(struct fib_table *tb, const struct flowi *flp,
                 }
 
                 if (IS_LEAF(n)) {
-                        ret = check_leaf(t, (struct leaf *)n, key, flp, res);
+                        ret = check_leaf(t, (struct leaf *)n, key, flp, res, fib_flags);
                         if (ret > 0)
                                 goto backtrace;
                         goto found;
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;
 }