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Commit 0197aa38 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

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: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 82efee14

net/ipv4/route.c

+12 −26
Original line number Diff line number Diff line
@@ -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);