ipv4: Simplify output route creation call sequence.

There's a lot of redundancy and unnecessary stack frames
in the output route creation path.

1) Make __mkroute_output() return error pointers.

2) Eliminate ip_mkroute_output() entirely, made possible by #1.

3) Call __mkroute_output() directly and handling the returning error
   pointers in ip_route_output_slow().

Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 756f544..849be48 100644 (file)
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2323,33 +2323,32 @@ 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,
-                           const struct flowi *oldflp,
-                           struct net_device *dev_out,
-                           unsigned flags)
+static struct rtable *__mkroute_output(struct fib_result *res,
+                                      const struct flowi *fl,
+                                      const struct flowi *oldflp,
+                                      struct net_device *dev_out,
+                                      unsigned int flags)
 {
-       struct rtable *rth;
-       struct in_device *in_dev;
        u32 tos = RT_FL_TOS(oldflp);
+       struct in_device *in_dev;
+       struct rtable *rth;
 
        if (ipv4_is_loopback(fl->fl4_src) && !(dev_out->flags & IFF_LOOPBACK))
-               return -EINVAL;
+               return ERR_PTR(-EINVAL);
 
        if (ipv4_is_lbcast(fl->fl4_dst))
                res->type = RTN_BROADCAST;
        else if (ipv4_is_multicast(fl->fl4_dst))
                res->type = RTN_MULTICAST;
        else if (ipv4_is_zeronet(fl->fl4_dst))
-               return -EINVAL;
+               return ERR_PTR(-EINVAL);
 
        if (dev_out->flags & IFF_LOOPBACK)
                flags |= RTCF_LOCAL;
 
        in_dev = __in_dev_get_rcu(dev_out);
        if (!in_dev)
-               return -EINVAL;
+               return ERR_PTR(-EINVAL);
 
        if (res->type == RTN_BROADCAST) {
                flags |= RTCF_BROADCAST | RTCF_LOCAL;
@@ -2370,7 +2369,7 @@ static int __mkroute_output(struct rtable **result,
 
        rth = dst_alloc(&ipv4_dst_ops);
        if (!rth)
-               return -ENOBUFS;
+               return ERR_PTR(-ENOBUFS);
 
        atomic_set(&rth->dst.__refcnt, 1);
        rth->dst.flags= DST_HOST;
@@ -2425,28 +2424,7 @@ static int __mkroute_output(struct rtable **result,
        rt_set_nexthop(rth, res, 0);
 
        rth->rt_flags = flags;
-       *result = rth;
-       return 0;
-}
-
-/* called with rcu_read_lock() */
-static int ip_mkroute_output(struct rtable **rp,
-                            struct fib_result *res,
-                            const struct flowi *fl,
-                            const struct flowi *oldflp,
-                            struct net_device *dev_out,
-                            unsigned flags)
-{
-       struct rtable *rth = NULL;
-       int err = __mkroute_output(&rth, res, fl, oldflp, dev_out, flags);
-       unsigned hash;
-       if (err == 0) {
-               hash = rt_hash(oldflp->fl4_dst, oldflp->fl4_src, oldflp->oif,
-                              rt_genid(dev_net(dev_out)));
-               err = rt_intern_hash(hash, rth, rp, NULL, oldflp->oif);
-       }
-
-       return err;
+       return rth;
 }
 
 /*
@@ -2469,6 +2447,7 @@ 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;
+       struct rtable *rth;
        int err;
 
 
@@ -2627,7 +2606,16 @@ 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);
+       rth = __mkroute_output(&res, &fl, oldflp, dev_out, flags);
+       if (IS_ERR(rth))
+               err = PTR_ERR(rth);
+       else {
+               unsigned int hash;
+
+               hash = rt_hash(oldflp->fl4_dst, oldflp->fl4_src, oldflp->oif,
+                              rt_genid(dev_net(dev_out)));
+               err = rt_intern_hash(hash, rth, rp, NULL, oldflp->oif);
+       }
 
 out:   return err;
 }