ipv4: Optimization for fib_info lookup with nexthops

Be optimistic about re-using a fib_info when nexthop id is given and
the route does not use metrics. Avoids a memory allocation which in
most cases is expected to be freed anyways.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 2c24d8e..0de895c 100644 (file)
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -325,14 +325,32 @@ static inline unsigned int fib_devindex_hashfn(unsigned int val)
                (val >> (DEVINDEX_HASHBITS * 2))) & mask;
 }
 
-static inline unsigned int fib_info_hashfn(const struct fib_info *fi)
+static unsigned int fib_info_hashfn_1(int init_val, u8 protocol, u8 scope,
+                                     u32 prefsrc, u32 priority)
+{
+       unsigned int val = init_val;
+
+       val ^= (protocol << 8) | scope;
+       val ^= prefsrc;
+       val ^= priority;
+
+       return val;
+}
+
+static unsigned int fib_info_hashfn_result(unsigned int val)
 {
        unsigned int mask = (fib_info_hash_size - 1);
-       unsigned int val = fi->fib_nhs;
 
-       val ^= (fi->fib_protocol << 8) | fi->fib_scope;
-       val ^= (__force u32)fi->fib_prefsrc;
-       val ^= fi->fib_priority;
+       return (val ^ (val >> 7) ^ (val >> 12)) & mask;
+}
+
+static inline unsigned int fib_info_hashfn(struct fib_info *fi)
+{
+       unsigned int val;
+
+       val = fib_info_hashfn_1(fi->fib_nhs, fi->fib_protocol,
+                               fi->fib_scope, (__force u32)fi->fib_prefsrc,
+                               fi->fib_priority);
 
        if (fi->nh) {
                val ^= fib_devindex_hashfn(fi->nh->id);
@@ -342,7 +360,40 @@ static inline unsigned int fib_info_hashfn(const struct fib_info *fi)
                } endfor_nexthops(fi)
        }
 
-       return (val ^ (val >> 7) ^ (val >> 12)) & mask;
+       return fib_info_hashfn_result(val);
+}
+
+/* no metrics, only nexthop id */
+static struct fib_info *fib_find_info_nh(struct net *net,
+                                        const struct fib_config *cfg)
+{
+       struct hlist_head *head;
+       struct fib_info *fi;
+       unsigned int hash;
+
+       hash = fib_info_hashfn_1(fib_devindex_hashfn(cfg->fc_nh_id),
+                                cfg->fc_protocol, cfg->fc_scope,
+                                (__force u32)cfg->fc_prefsrc,
+                                cfg->fc_priority);
+       hash = fib_info_hashfn_result(hash);
+       head = &fib_info_hash[hash];
+
+       hlist_for_each_entry(fi, head, fib_hash) {
+               if (!net_eq(fi->fib_net, net))
+                       continue;
+               if (!fi->nh || fi->nh->id != cfg->fc_nh_id)
+                       continue;
+               if (cfg->fc_protocol == fi->fib_protocol &&
+                   cfg->fc_scope == fi->fib_scope &&
+                   cfg->fc_prefsrc == fi->fib_prefsrc &&
+                   cfg->fc_priority == fi->fib_priority &&
+                   cfg->fc_type == fi->fib_type &&
+                   cfg->fc_table == fi->fib_tb_id &&
+                   !((cfg->fc_flags ^ fi->fib_flags) & ~RTNH_COMPARE_MASK))
+                       return fi;
+       }
+
+       return NULL;
 }
 
 static struct fib_info *fib_find_info(struct fib_info *nfi)
@@ -1309,6 +1360,14 @@ struct fib_info *fib_create_info(struct fib_config *cfg,
        }
 
        if (cfg->fc_nh_id) {
+               if (!cfg->fc_mx) {
+                       fi = fib_find_info_nh(net, cfg);
+                       if (fi) {
+                               fi->fib_treeref++;
+                               return fi;
+                       }
+               }
+
                nh = nexthop_find_by_id(net, cfg->fc_nh_id);
                if (!nh) {
                        NL_SET_ERR_MSG(extack, "Nexthop id does not exist");