From 0197aa38df2ce550c0bfc96194b07ce6b68af814 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 30 Sep 2010 03:33:58 +0000 Subject: [PATCH] ipv4: rcu conversion in ip_route_output_slow ip_route_output_slow() is enclosed in an rcu_read_lock() protected section, so that no references are taken/released on device, thanks to __ip_dev_find() & dev_get_by_index_rcu() Tested with ip route cache disabled, and a stress test : Before patch: elapsed time : real 1m38.347s user 0m11.909s sys 23m51.501s Profile: 13788.00 22.7% ip_route_output_slow [kernel] 7875.00 13.0% dst_destroy [kernel] 3925.00 6.5% fib_semantic_match [kernel] 3144.00 5.2% fib_rules_lookup [kernel] 3061.00 5.0% dst_alloc [kernel] 2276.00 3.7% rt_set_nexthop [kernel] 1762.00 2.9% fib_table_lookup [kernel] 1538.00 2.5% _raw_read_lock [kernel] 1358.00 2.2% ip_output [kernel] After patch: real 1m28.808s user 0m13.245s sys 20m37.293s 10950.00 17.2% ip_route_output_slow [kernel] 10726.00 16.9% dst_destroy [kernel] 5170.00 8.1% fib_semantic_match [kernel] 3937.00 6.2% dst_alloc [kernel] 3635.00 5.7% rt_set_nexthop [kernel] 2900.00 4.6% fib_rules_lookup [kernel] 2240.00 3.5% fib_table_lookup [kernel] 1427.00 2.2% _raw_read_lock [kernel] 1157.00 1.8% kmem_cache_alloc [kernel] Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/route.c | 38 ++++++++++++-------------------------- 1 file changed, 12 insertions(+), 26 deletions(-) diff --git a/net/ipv4/route.c b/net/ipv4/route.c index ea89500..a61acea 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -2487,6 +2487,7 @@ static int ip_mkroute_output(struct rtable **rp, /* * Major route resolver routine. + * called with rcu_read_lock(); */ static int ip_route_output_slow(struct net *net, struct rtable **rp, @@ -2505,7 +2506,7 @@ static int ip_route_output_slow(struct net *net, struct rtable **rp, .iif = net->loopback_dev->ifindex, .oif = oldflp->oif }; struct fib_result res; - unsigned flags = 0; + unsigned int flags = 0; struct net_device *dev_out = NULL; int free_res = 0; int err; @@ -2535,7 +2536,7 @@ static int ip_route_output_slow(struct net *net, struct rtable **rp, (ipv4_is_multicast(oldflp->fl4_dst) || oldflp->fl4_dst == htonl(0xFFFFFFFF))) { /* It is equivalent to inet_addr_type(saddr) == RTN_LOCAL */ - dev_out = ip_dev_find(net, oldflp->fl4_src); + dev_out = __ip_dev_find(net, oldflp->fl4_src, false); if (dev_out == NULL) goto out; @@ -2560,26 +2561,21 @@ static int ip_route_output_slow(struct net *net, struct rtable **rp, if (!(oldflp->flags & FLOWI_FLAG_ANYSRC)) { /* It is equivalent to inet_addr_type(saddr) == RTN_LOCAL */ - dev_out = ip_dev_find(net, oldflp->fl4_src); - if (dev_out == NULL) + if (!__ip_dev_find(net, oldflp->fl4_src, false)) goto out; - dev_put(dev_out); - dev_out = NULL; } } if (oldflp->oif) { - dev_out = dev_get_by_index(net, oldflp->oif); + dev_out = dev_get_by_index_rcu(net, oldflp->oif); err = -ENODEV; if (dev_out == NULL) goto out; /* RACE: Check return value of inet_select_addr instead. */ - if (rcu_dereference_raw(dev_out->ip_ptr) == NULL) { - dev_put(dev_out); + if (rcu_dereference(dev_out->ip_ptr) == NULL) goto out; /* Wrong error code */ - } if (ipv4_is_local_multicast(oldflp->fl4_dst) || oldflp->fl4_dst == htonl(0xFFFFFFFF)) { @@ -2602,10 +2598,7 @@ static int ip_route_output_slow(struct net *net, struct rtable **rp, fl.fl4_dst = fl.fl4_src; if (!fl.fl4_dst) fl.fl4_dst = fl.fl4_src = htonl(INADDR_LOOPBACK); - if (dev_out) - dev_put(dev_out); dev_out = net->loopback_dev; - dev_hold(dev_out); fl.oif = net->loopback_dev->ifindex; res.type = RTN_LOCAL; flags |= RTCF_LOCAL; @@ -2639,8 +2632,6 @@ static int ip_route_output_slow(struct net *net, struct rtable **rp, res.type = RTN_UNICAST; goto make_route; } - if (dev_out) - dev_put(dev_out); err = -ENETUNREACH; goto out; } @@ -2649,10 +2640,7 @@ static int ip_route_output_slow(struct net *net, struct rtable **rp, if (res.type == RTN_LOCAL) { if (!fl.fl4_src) fl.fl4_src = fl.fl4_dst; - if (dev_out) - dev_put(dev_out); dev_out = net->loopback_dev; - dev_hold(dev_out); fl.oif = dev_out->ifindex; if (res.fi) fib_info_put(res.fi); @@ -2672,28 +2660,23 @@ static int ip_route_output_slow(struct net *net, struct rtable **rp, if (!fl.fl4_src) fl.fl4_src = FIB_RES_PREFSRC(res); - if (dev_out) - dev_put(dev_out); dev_out = FIB_RES_DEV(res); - dev_hold(dev_out); fl.oif = dev_out->ifindex; make_route: err = ip_mkroute_output(rp, &res, &fl, oldflp, dev_out, flags); - if (free_res) fib_res_put(&res); - if (dev_out) - dev_put(dev_out); out: return err; } int __ip_route_output_key(struct net *net, struct rtable **rp, const struct flowi *flp) { - unsigned hash; + unsigned int hash; + int res; struct rtable *rth; if (!rt_caching(net)) @@ -2724,7 +2707,10 @@ int __ip_route_output_key(struct net *net, struct rtable **rp, rcu_read_unlock_bh(); slow_output: - return ip_route_output_slow(net, rp, flp); + rcu_read_lock(); + res = ip_route_output_slow(net, rp, flp); + rcu_read_unlock(); + return res; } EXPORT_SYMBOL_GPL(__ip_route_output_key); -- 2.7.4