Commit e67f88dd authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: dont hold rtnl mutex during netlink dump callbacks 



Four years ago, Patrick made a change to hold rtnl mutex during netlink
dump callbacks.

I believe it was a wrong move. This slows down concurrent dumps, making
good old /proc/net/ files faster than rtnetlink in some situations.

This occurred to me because one "ip link show dev ..." was _very_ slow
on a workload adding/removing network devices in background.

All dump callbacks are able to use RCU locking now, so this patch does
roughly a revert of commits :

1c2d670f : [RTNETLINK]: Hold rtnl_mutex during netlink dump callbacks
6313c1e0 : [RTNETLINK]: Remove unnecessary locking in dump callbacks

This let writers fight for rtnl mutex and readers going full speed.

It also takes care of phonet : phonet_route_get() is now called from rcu
read section. I renamed it to phonet_route_get_rcu()

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Remi Denis-Courmont <remi.denis-courmont@nokia.com>
Acked-by: default avatarStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent dcfd9cdc

include/net/phonet/pn_dev.h

+1 −1
Original line number Diff line number Diff line
@@ -51,7 +51,7 @@ void phonet_address_notify(int event, struct net_device *dev, u8 addr); 
int phonet_route_add(struct net_device *dev, u8 daddr);

int phonet_route_del(struct net_device *dev, u8 daddr);

void rtm_phonet_notify(int event, struct net_device *dev, u8 dst);

struct net_device *phonet_route_get(struct net *net, u8 daddr);

struct net_device *phonet_route_get_rcu(struct net *net, u8 daddr);

struct net_device *phonet_route_output(struct net *net, u8 daddr);



#define PN_NO_ADDR	0xff

net/bridge/br_netlink.c

+4 −3
Original line number Diff line number Diff line
@@ -120,8 +120,9 @@ static int br_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb) 
	int idx;



	idx = 0;

	for_each_netdev(net, dev) {

		struct net_bridge_port *port = br_port_get_rtnl(dev);

	rcu_read_lock();

	for_each_netdev_rcu(net, dev) {

		struct net_bridge_port *port = br_port_get_rcu(dev);



		/* not a bridge port */

		if (!port || idx < cb->args[0])
@@ -135,7 +136,7 @@ static int br_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb) 
skip:

		++idx;

	}



	rcu_read_unlock();

	cb->args[0] = idx;



	return skb->len;

net/core/fib_rules.c

+2 −1
Original line number Diff line number Diff line
@@ -590,7 +590,8 @@ static int dump_rules(struct sk_buff *skb, struct netlink_callback *cb, 
	int idx = 0;

	struct fib_rule *rule;



	list_for_each_entry(rule, &ops->rules_list, list) {

	rcu_read_lock();

	list_for_each_entry_rcu(rule, &ops->rules_list, list) {

		if (idx < cb->args[1])

			goto skip;

net/core/rtnetlink.c

+5 −7
Original line number Diff line number Diff line
@@ -1007,10 +1007,11 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb) 
	s_h = cb->args[0];

	s_idx = cb->args[1];



	rcu_read_lock();

	for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {

		idx = 0;

		head = &net->dev_index_head[h];

		hlist_for_each_entry(dev, node, head, index_hlist) {

		hlist_for_each_entry_rcu(dev, node, head, index_hlist) {

			if (idx < s_idx)

				goto cont;

			if (rtnl_fill_ifinfo(skb, dev, RTM_NEWLINK,
@@ -1023,6 +1024,7 @@ cont: 
		}

	}

out:

	rcu_read_unlock();

	cb->args[1] = idx;

	cb->args[0] = h;
@@ -1879,7 +1881,6 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh) 
	int min_len;

	int family;

	int type;

	int err;



	type = nlh->nlmsg_type;

	if (type > RTM_MAX)
@@ -1906,11 +1907,8 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh) 
		if (dumpit == NULL)

			return -EOPNOTSUPP;



		__rtnl_unlock();

		rtnl = net->rtnl;

		err = netlink_dump_start(rtnl, skb, nlh, dumpit, NULL);

		rtnl_lock();

		return err;

		return netlink_dump_start(rtnl, skb, nlh, dumpit, NULL);

	}



	memset(rta_buf, 0, (rtattr_max * sizeof(struct rtattr *)));
@@ -1980,7 +1978,7 @@ static int __net_init rtnetlink_net_init(struct net *net) 
{

	struct sock *sk;

	sk = netlink_kernel_create(net, NETLINK_ROUTE, RTNLGRP_MAX,

				   rtnetlink_rcv, &rtnl_mutex, THIS_MODULE);

				   rtnetlink_rcv, NULL, THIS_MODULE);

	if (!sk)

		return -ENOMEM;

	net->rtnl = sk;

net/decnet/dn_dev.c

+6 −4
Original line number Diff line number Diff line
@@ -752,7 +752,8 @@ static int dn_nl_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb) 
	skip_naddr = cb->args[1];



	idx = 0;

	for_each_netdev(&init_net, dev) {

	rcu_read_lock();

	for_each_netdev_rcu(&init_net, dev) {

		if (idx < skip_ndevs)

			goto cont;

		else if (idx > skip_ndevs) {
@@ -761,11 +762,11 @@ static int dn_nl_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb) 
			skip_naddr = 0;

		}



		if ((dn_db = rtnl_dereference(dev->dn_ptr)) == NULL)

		if ((dn_db = rcu_dereference(dev->dn_ptr)) == NULL)

			goto cont;



		for (ifa = rtnl_dereference(dn_db->ifa_list), dn_idx = 0; ifa;

		     ifa = rtnl_dereference(ifa->ifa_next), dn_idx++) {

		for (ifa = rcu_dereference(dn_db->ifa_list), dn_idx = 0; ifa;

		     ifa = rcu_dereference(ifa->ifa_next), dn_idx++) {

			if (dn_idx < skip_naddr)

				continue;
@@ -778,6 +779,7 @@ cont: 
		idx++;

	}

done:

	rcu_read_unlock();

	cb->args[0] = idx;

	cb->args[1] = dn_idx;

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