gre: optimize hash lookup

Instead of keeping candidate tunnel device from all categories,
keep only one candidate with best score. This optimizes stack
usage and speeds up exit code.

Signed-off-by: Timo Teras <timo.teras@iki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 4a43739..07a188a 100644 (file)
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -172,11 +172,11 @@ static struct ip_tunnel * ipgre_tunnel_lookup(struct net_device *dev,
        int link = dev->ifindex;
        unsigned h0 = HASH(remote);
        unsigned h1 = HASH(key);
-       struct ip_tunnel *t, *sel[4] = { NULL, NULL, NULL, NULL };
+       struct ip_tunnel *t, *cand = NULL;
        struct ipgre_net *ign = net_generic(net, ipgre_net_id);
        int dev_type = (gre_proto == htons(ETH_P_TEB)) ?
                       ARPHRD_ETHER : ARPHRD_IPGRE;
-       int idx;
+       int score, cand_score = 4;
 
        for (t = ign->tunnels_r_l[h0^h1]; t; t = t->next) {
                if (local != t->parms.iph.saddr ||
@@ -189,15 +189,18 @@ static struct ip_tunnel * ipgre_tunnel_lookup(struct net_device *dev,
                    t->dev->type != dev_type)
                        continue;
 
-               idx = 0;
+               score = 0;
                if (t->parms.link != link)
-                       idx |= 1;
+                       score |= 1;
                if (t->dev->type != dev_type)
-                       idx |= 2;
-               if (idx == 0)
+                       score |= 2;
+               if (score == 0)
                        return t;
-               if (sel[idx] == NULL)
-                       sel[idx] = t;
+
+               if (score < cand_score) {
+                       cand = t;
+                       cand_score = score;
+               }
        }
 
        for (t = ign->tunnels_r[h0^h1]; t; t = t->next) {
@@ -210,15 +213,18 @@ static struct ip_tunnel * ipgre_tunnel_lookup(struct net_device *dev,
                    t->dev->type != dev_type)
                        continue;
 
-               idx = 0;
+               score = 0;
                if (t->parms.link != link)
-                       idx |= 1;
+                       score |= 1;
                if (t->dev->type != dev_type)
-                       idx |= 2;
-               if (idx == 0)
+                       score |= 2;
+               if (score == 0)
                        return t;
-               if (sel[idx] == NULL)
-                       sel[idx] = t;
+
+               if (score < cand_score) {
+                       cand = t;
+                       cand_score = score;
+               }
        }
 
        for (t = ign->tunnels_l[h1]; t; t = t->next) {
@@ -233,15 +239,18 @@ static struct ip_tunnel * ipgre_tunnel_lookup(struct net_device *dev,
                    t->dev->type != dev_type)
                        continue;
 
-               idx = 0;
+               score = 0;
                if (t->parms.link != link)
-                       idx |= 1;
+                       score |= 1;
                if (t->dev->type != dev_type)
-                       idx |= 2;
-               if (idx == 0)
+                       score |= 2;
+               if (score == 0)
                        return t;
-               if (sel[idx] == NULL)
-                       sel[idx] = t;
+
+               if (score < cand_score) {
+                       cand = t;
+                       cand_score = score;
+               }
        }
 
        for (t = ign->tunnels_wc[h1]; t; t = t->next) {
@@ -253,20 +262,22 @@ static struct ip_tunnel * ipgre_tunnel_lookup(struct net_device *dev,
                    t->dev->type != dev_type)
                        continue;
 
-               idx = 0;
+               score = 0;
                if (t->parms.link != link)
-                       idx |= 1;
+                       score |= 1;
                if (t->dev->type != dev_type)
-                       idx |= 2;
-               if (idx == 0)
+                       score |= 2;
+               if (score == 0)
                        return t;
-               if (sel[idx] == NULL)
-                       sel[idx] = t;
+
+               if (score < cand_score) {
+                       cand = t;
+                       cand_score = score;
+               }
        }
 
-       for (idx = 1; idx < ARRAY_SIZE(sel); idx++)
-               if (sel[idx] != NULL)
-                       return sel[idx];
+       if (cand != NULL)
+               return cand;
 
        if (ign->fb_tunnel_dev->flags & IFF_UP)
                return netdev_priv(ign->fb_tunnel_dev);