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>

1 files changed, 40 insertions, 29 deletions

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 4a43739c9035..07a188afb3ac 100644
--- 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);