fib_trie: Push rcu_read_lock/unlock to callers

This change is to start cleaning up some of the rcu_read_lock/unlock
handling.  I realized while reviewing the code there are several spots that
I don't believe are being handled correctly or are masking warnings by
locally calling rcu_read_lock/unlock instead of calling them at the correct
level.

A common example is a call to fib_get_table followed by fib_table_lookup.
The rcu_read_lock/unlock ought to wrap both but there are several spots where
they were not wrapped.

Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 114 insertions, 122 deletions

diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index 09a819ee2151..5bd120e4bc0a 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -222,16 +222,19 @@ static inline struct fib_table *fib_new_table(struct net *net, u32 id)
 static inline int fib_lookup(struct net *net, const struct flowi4 *flp,
                              struct fib_result *res)
 {
-        struct fib_table *table;
+        int err = -ENETUNREACH;
+
+        rcu_read_lock();
+
+        if (!fib_table_lookup(fib_get_table(net, RT_TABLE_LOCAL), flp, res,
+                              FIB_LOOKUP_NOREF) ||
+            !fib_table_lookup(fib_get_table(net, RT_TABLE_MAIN), flp, res,
+                              FIB_LOOKUP_NOREF))
+                err = 0;
 
-        table = fib_get_table(net, RT_TABLE_LOCAL);
-        if (!fib_table_lookup(table, flp, res, FIB_LOOKUP_NOREF))
-                return 0;
+        rcu_read_unlock();
 
-        table = fib_get_table(net, RT_TABLE_MAIN);
-        if (!fib_table_lookup(table, flp, res, FIB_LOOKUP_NOREF))
-                return 0;
-        return -ENETUNREACH;
+        return err;
 }
 
 #else /* CONFIG_IP_MULTIPLE_TABLES */
@@ -247,20 +250,25 @@ static inline int fib_lookup(struct net *net, struct flowi4 *flp,
                              struct fib_result *res)
 {
         if (!net->ipv4.fib_has_custom_rules) {
+                int err = -ENETUNREACH;
+
+                rcu_read_lock();
+
                 res->tclassid = 0;
-                if (net->ipv4.fib_local &&
-                    !fib_table_lookup(net->ipv4.fib_local, flp, res,
-                                      FIB_LOOKUP_NOREF))
-                        return 0;
-                if (net->ipv4.fib_main &&
-                    !fib_table_lookup(net->ipv4.fib_main, flp, res,
-                                      FIB_LOOKUP_NOREF))
-                        return 0;
-                if (net->ipv4.fib_default &&
-                    !fib_table_lookup(net->ipv4.fib_default, flp, res,
-                                      FIB_LOOKUP_NOREF))
-                        return 0;
-                return -ENETUNREACH;
+                if ((net->ipv4.fib_local &&
+                     !fib_table_lookup(net->ipv4.fib_local, flp, res,
+                                       FIB_LOOKUP_NOREF)) ||
+                    (net->ipv4.fib_main &&
+                     !fib_table_lookup(net->ipv4.fib_main, flp, res,
+                                       FIB_LOOKUP_NOREF)) ||
+                    (net->ipv4.fib_default &&
+                     !fib_table_lookup(net->ipv4.fib_default, flp, res,
+                                       FIB_LOOKUP_NOREF)))
+                        err = 0;
+
+                rcu_read_unlock();
+
+                return err;
         }
         return __fib_lookup(net, flp, res);
 }
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 66890209208f..57be71dd6a9e 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -109,6 +109,7 @@ struct fib_table *fib_new_table(struct net *net, u32 id)
         return tb;
 }
 
+/* caller must hold either rtnl or rcu read lock */
 struct fib_table *fib_get_table(struct net *net, u32 id)
 {
         struct fib_table *tb;
@@ -119,15 +120,11 @@ struct fib_table *fib_get_table(struct net *net, u32 id)
                 id = RT_TABLE_MAIN;
         h = id & (FIB_TABLE_HASHSZ - 1);
 
-        rcu_read_lock();
         head = &net->ipv4.fib_table_hash[h];
         hlist_for_each_entry_rcu(tb, head, tb_hlist) {
-                if (tb->tb_id == id) {
-                        rcu_read_unlock();
+                if (tb->tb_id == id)
                         return tb;
-                }
         }
-        rcu_read_unlock();
         return NULL;
 }
 #endif /* CONFIG_IP_MULTIPLE_TABLES */
@@ -167,16 +164,18 @@ static inline unsigned int __inet_dev_addr_type(struct net *net,
         if (ipv4_is_multicast(addr))
                 return RTN_MULTICAST;
 
+        rcu_read_lock();
+
         local_table = fib_get_table(net, RT_TABLE_LOCAL);
         if (local_table) {
                 ret = RTN_UNICAST;
-                rcu_read_lock();
                 if (!fib_table_lookup(local_table, &fl4, &res, FIB_LOOKUP_NOREF)) {
                         if (!dev || dev == res.fi->fib_dev)
                                 ret = res.type;
                 }
-                rcu_read_unlock();
         }
+
+        rcu_read_unlock();
         return ret;
 }
 
@@ -919,7 +918,7 @@ void fib_del_ifaddr(struct in_ifaddr *ifa, struct in_ifaddr *iprim)
 #undef BRD1_OK
 }
 
-static void nl_fib_lookup(struct fib_result_nl *frn, struct fib_table *tb)
+static void nl_fib_lookup(struct net *net, struct fib_result_nl *frn)
 {
 
         struct fib_result       res;
@@ -929,6 +928,11 @@ static void nl_fib_lookup(struct fib_result_nl *frn, struct fib_table *tb)
                 .flowi4_tos = frn->fl_tos,
                 .flowi4_scope = frn->fl_scope,
         };
+        struct fib_table *tb;
+
+        rcu_read_lock();
+
+        tb = fib_get_table(net, frn->tb_id_in);
 
         frn->err = -ENOENT;
         if (tb) {
@@ -945,6 +949,8 @@ static void nl_fib_lookup(struct fib_result_nl *frn, struct fib_table *tb)
                 }
                 local_bh_enable();
         }
+
+        rcu_read_unlock();
 }
 
 static void nl_fib_input(struct sk_buff *skb)
@@ -952,7 +958,6 @@ static void nl_fib_input(struct sk_buff *skb)
         struct net *net;
         struct fib_result_nl *frn;
         struct nlmsghdr *nlh;
-        struct fib_table *tb;
         u32 portid;
 
         net = sock_net(skb->sk);
@@ -967,9 +972,7 @@ static void nl_fib_input(struct sk_buff *skb)
         nlh = nlmsg_hdr(skb);
 
         frn = (struct fib_result_nl *) nlmsg_data(nlh);
-        tb = fib_get_table(net, frn->tb_id_in);
-
-        nl_fib_lookup(frn, tb);
+        nl_fib_lookup(net, frn);
 
         portid = NETLINK_CB(skb).portid;      /* netlink portid */
         NETLINK_CB(skb).portid = 0;        /* from kernel */
diff --git a/net/ipv4/fib_rules.c b/net/ipv4/fib_rules.c
index 8f7bd56955b0..d3db718be51d 100644
--- a/net/ipv4/fib_rules.c
+++ b/net/ipv4/fib_rules.c
@@ -81,27 +81,25 @@ static int fib4_rule_action(struct fib_rule *rule, struct flowi *flp,
                 break;
 
         case FR_ACT_UNREACHABLE:
-                err = -ENETUNREACH;
-                goto errout;
+                return -ENETUNREACH;
 
         case FR_ACT_PROHIBIT:
-                err = -EACCES;
-                goto errout;
+                return -EACCES;
 
         case FR_ACT_BLACKHOLE:
         default:
-                err = -EINVAL;
-                goto errout;
+                return -EINVAL;
         }
 
+        rcu_read_lock();
+
         tbl = fib_get_table(rule->fr_net, rule->table);
-        if (!tbl)
-                goto errout;
+        if (tbl)
+                err = fib_table_lookup(tbl, &flp->u.ip4,
+                                       (struct fib_result *)arg->result,
+                                       arg->flags);
 
-        err = fib_table_lookup(tbl, &flp->u.ip4, (struct fib_result *) arg->result, arg->flags);
-        if (err > 0)
-                err = -EAGAIN;
-errout:
+        rcu_read_unlock();
         return err;
 }
 
diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 28a3065470bc..987b06d1effe 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -1181,72 +1181,6 @@ err:
         return err;
 }
 
-/* should be called with rcu_read_lock */
-static int check_leaf(struct fib_table *tb, struct trie *t, struct tnode *l,
-                      t_key key,  const struct flowi4 *flp,
-                      struct fib_result *res, int fib_flags)
-{
-        struct leaf_info *li;
-        struct hlist_head *hhead = &l->list;
-
-        hlist_for_each_entry_rcu(li, hhead, hlist) {
-                struct fib_alias *fa;
-
-                if (l->key != (key & li->mask_plen))
-                        continue;
-
-                list_for_each_entry_rcu(fa, &li->falh, fa_list) {
-                        struct fib_info *fi = fa->fa_info;
-                        int nhsel, err;
-
-                        if (fa->fa_tos && fa->fa_tos != flp->flowi4_tos)
-                                continue;
-                        if (fi->fib_dead)
-                                continue;
-                        if (fa->fa_info->fib_scope < flp->flowi4_scope)
-                                continue;
-                        fib_alias_accessed(fa);
-                        err = fib_props[fa->fa_type].error;
-                        if (unlikely(err < 0)) {
-#ifdef CONFIG_IP_FIB_TRIE_STATS
-                                this_cpu_inc(t->stats->semantic_match_passed);
-#endif
-                                return err;
-                        }
-                        if (fi->fib_flags & RTNH_F_DEAD)
-                                continue;
-                        for (nhsel = 0; nhsel < fi->fib_nhs; nhsel++) {
-                                const struct fib_nh *nh = &fi->fib_nh[nhsel];
-
-                                if (nh->nh_flags & RTNH_F_DEAD)
-                                        continue;
-                                if (flp->flowi4_oif && flp->flowi4_oif != nh->nh_oif)
-                                        continue;
-
-#ifdef CONFIG_IP_FIB_TRIE_STATS
-                                this_cpu_inc(t->stats->semantic_match_passed);
-#endif
-                                res->prefixlen = li->plen;
-                                res->nh_sel = nhsel;
-                                res->type = fa->fa_type;
-                                res->scope = fi->fib_scope;
-                                res->fi = fi;
-                                res->table = tb;
-                                res->fa_head = &li->falh;
-                                if (!(fib_flags & FIB_LOOKUP_NOREF))
-                                        atomic_inc(&fi->fib_clntref);
-                                return 0;
-                        }
-                }
-
-#ifdef CONFIG_IP_FIB_TRIE_STATS
-                this_cpu_inc(t->stats->semantic_match_miss);
-#endif
-        }
-
-        return 1;
-}
-
 static inline t_key prefix_mismatch(t_key key, struct tnode *n)
 {
         t_key prefix = n->key;
@@ -1254,6 +1188,7 @@ static inline t_key prefix_mismatch(t_key key, struct tnode *n)
         return (key ^ prefix) & (prefix | -prefix);
 }
 
+/* should be called with rcu_read_lock */
 int fib_table_lookup(struct fib_table *tb, const struct flowi4 *flp,
                      struct fib_result *res, int fib_flags)
 {
@@ -1263,14 +1198,12 @@ int fib_table_lookup(struct fib_table *tb, const struct flowi4 *flp,
 #endif
         const t_key key = ntohl(flp->daddr);
         struct tnode *n, *pn;
+        struct leaf_info *li;
         t_key cindex;
-        int ret = 1;
-
-        rcu_read_lock();
 
         n = rcu_dereference(t->trie);
         if (!n)
-                goto failed;
+                return -EAGAIN;
 
 #ifdef CONFIG_IP_FIB_TRIE_STATS
         this_cpu_inc(stats->gets);
@@ -1350,7 +1283,7 @@ backtrace:
 
                                 pn = node_parent_rcu(pn);
                                 if (unlikely(!pn))
-                                        goto failed;
+                                        return -EAGAIN;
 #ifdef CONFIG_IP_FIB_TRIE_STATS
                                 this_cpu_inc(stats->backtrack);
 #endif
@@ -1368,12 +1301,62 @@ backtrace:
 
 found:
         /* Step 3: Process the leaf, if that fails fall back to backtracing */
-        ret = check_leaf(tb, t, n, key, flp, res, fib_flags);
-        if (unlikely(ret > 0))
-                goto backtrace;
-failed:
-        rcu_read_unlock();
-        return ret;
+        hlist_for_each_entry_rcu(li, &n->list, hlist) {
+                struct fib_alias *fa;
+
+                if ((key ^ n->key) & li->mask_plen)
+                        continue;
+
+                list_for_each_entry_rcu(fa, &li->falh, fa_list) {
+                        struct fib_info *fi = fa->fa_info;
+                        int nhsel, err;
+
+                        if (fa->fa_tos && fa->fa_tos != flp->flowi4_tos)
+                                continue;
+                        if (fi->fib_dead)
+                                continue;
+                        if (fa->fa_info->fib_scope < flp->flowi4_scope)
+                                continue;
+                        fib_alias_accessed(fa);
+                        err = fib_props[fa->fa_type].error;
+                        if (unlikely(err < 0)) {
+#ifdef CONFIG_IP_FIB_TRIE_STATS
+                                this_cpu_inc(stats->semantic_match_passed);
+#endif
+                                return err;
+                        }
+                        if (fi->fib_flags & RTNH_F_DEAD)
+                                continue;
+                        for (nhsel = 0; nhsel < fi->fib_nhs; nhsel++) {
+                                const struct fib_nh *nh = &fi->fib_nh[nhsel];
+
+                                if (nh->nh_flags & RTNH_F_DEAD)
+                                        continue;
+                                if (flp->flowi4_oif && flp->flowi4_oif != nh->nh_oif)
+                                        continue;
+
+                                if (!(fib_flags & FIB_LOOKUP_NOREF))
+                                        atomic_inc(&fi->fib_clntref);
+
+                                res->prefixlen = li->plen;
+                                res->nh_sel = nhsel;
+                                res->type = fa->fa_type;
+                                res->scope = fi->fib_scope;
+                                res->fi = fi;
+                                res->table = tb;
+                                res->fa_head = &li->falh;
+#ifdef CONFIG_IP_FIB_TRIE_STATS
+                                this_cpu_inc(stats->semantic_match_passed);
+#endif
+                                return err;
+                        }
+                }
+
+#ifdef CONFIG_IP_FIB_TRIE_STATS
+                this_cpu_inc(stats->semantic_match_miss);
+#endif
+        }
+        goto backtrace;
 }
 EXPORT_SYMBOL_GPL(fib_table_lookup);