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 :1c2d670f36
: [RTNETLINK]: Hold rtnl_mutex during netlink dump callbacks6313c1e099
: [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: Eric Dumazet <eric.dumazet@gmail.com> Cc: Patrick McHardy <kaber@trash.net> Cc: Remi Denis-Courmont <remi.denis-courmont@nokia.com> Acked-by: Stephen Hemminger <shemminger@vyatta.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -51,7 +51,7 @@ void phonet_address_notify(int event, struct net_device *dev, u8 addr);
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int phonet_route_add(struct net_device *dev, u8 daddr);
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int phonet_route_del(struct net_device *dev, u8 daddr);
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void rtm_phonet_notify(int event, struct net_device *dev, u8 dst);
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struct net_device *phonet_route_get(struct net *net, u8 daddr);
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struct net_device *phonet_route_get_rcu(struct net *net, u8 daddr);
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struct net_device *phonet_route_output(struct net *net, u8 daddr);
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#define PN_NO_ADDR 0xff
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@ -120,8 +120,9 @@ static int br_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
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int idx;
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idx = 0;
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for_each_netdev(net, dev) {
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struct net_bridge_port *port = br_port_get_rtnl(dev);
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rcu_read_lock();
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for_each_netdev_rcu(net, dev) {
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struct net_bridge_port *port = br_port_get_rcu(dev);
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/* not a bridge port */
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if (!port || idx < cb->args[0])
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@ -135,7 +136,7 @@ static int br_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
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skip:
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++idx;
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}
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rcu_read_unlock();
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cb->args[0] = idx;
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return skb->len;
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@ -590,7 +590,8 @@ static int dump_rules(struct sk_buff *skb, struct netlink_callback *cb,
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int idx = 0;
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struct fib_rule *rule;
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list_for_each_entry(rule, &ops->rules_list, list) {
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rcu_read_lock();
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list_for_each_entry_rcu(rule, &ops->rules_list, list) {
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if (idx < cb->args[1])
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goto skip;
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@ -1007,10 +1007,11 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
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s_h = cb->args[0];
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s_idx = cb->args[1];
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rcu_read_lock();
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for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {
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idx = 0;
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head = &net->dev_index_head[h];
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hlist_for_each_entry(dev, node, head, index_hlist) {
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hlist_for_each_entry_rcu(dev, node, head, index_hlist) {
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if (idx < s_idx)
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goto cont;
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if (rtnl_fill_ifinfo(skb, dev, RTM_NEWLINK,
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@ -1023,6 +1024,7 @@ cont:
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}
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}
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out:
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rcu_read_unlock();
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cb->args[1] = idx;
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cb->args[0] = h;
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@ -1879,7 +1881,6 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
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int min_len;
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int family;
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int type;
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int err;
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type = nlh->nlmsg_type;
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if (type > RTM_MAX)
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@ -1906,11 +1907,8 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
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if (dumpit == NULL)
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return -EOPNOTSUPP;
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__rtnl_unlock();
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rtnl = net->rtnl;
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err = netlink_dump_start(rtnl, skb, nlh, dumpit, NULL);
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rtnl_lock();
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return err;
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return netlink_dump_start(rtnl, skb, nlh, dumpit, NULL);
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}
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memset(rta_buf, 0, (rtattr_max * sizeof(struct rtattr *)));
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@ -1980,7 +1978,7 @@ static int __net_init rtnetlink_net_init(struct net *net)
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{
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struct sock *sk;
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sk = netlink_kernel_create(net, NETLINK_ROUTE, RTNLGRP_MAX,
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rtnetlink_rcv, &rtnl_mutex, THIS_MODULE);
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rtnetlink_rcv, NULL, THIS_MODULE);
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if (!sk)
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return -ENOMEM;
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net->rtnl = sk;
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@ -752,7 +752,8 @@ static int dn_nl_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
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skip_naddr = cb->args[1];
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idx = 0;
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for_each_netdev(&init_net, dev) {
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rcu_read_lock();
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for_each_netdev_rcu(&init_net, dev) {
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if (idx < skip_ndevs)
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goto cont;
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else if (idx > skip_ndevs) {
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@ -761,11 +762,11 @@ static int dn_nl_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
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skip_naddr = 0;
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}
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if ((dn_db = rtnl_dereference(dev->dn_ptr)) == NULL)
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if ((dn_db = rcu_dereference(dev->dn_ptr)) == NULL)
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goto cont;
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for (ifa = rtnl_dereference(dn_db->ifa_list), dn_idx = 0; ifa;
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ifa = rtnl_dereference(ifa->ifa_next), dn_idx++) {
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for (ifa = rcu_dereference(dn_db->ifa_list), dn_idx = 0; ifa;
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ifa = rcu_dereference(ifa->ifa_next), dn_idx++) {
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if (dn_idx < skip_naddr)
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continue;
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@ -778,6 +779,7 @@ cont:
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idx++;
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}
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done:
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rcu_read_unlock();
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cb->args[0] = idx;
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cb->args[1] = dn_idx;
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@ -394,10 +394,11 @@ static int inet6_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
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arg.net = net;
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w->args = &arg;
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rcu_read_lock();
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for (h = s_h; h < FIB6_TABLE_HASHSZ; h++, s_e = 0) {
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e = 0;
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head = &net->ipv6.fib_table_hash[h];
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hlist_for_each_entry(tb, node, head, tb6_hlist) {
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hlist_for_each_entry_rcu(tb, node, head, tb6_hlist) {
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if (e < s_e)
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goto next;
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res = fib6_dump_table(tb, skb, cb);
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@ -408,6 +409,7 @@ next:
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}
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}
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out:
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rcu_read_unlock();
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cb->args[1] = e;
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cb->args[0] = h;
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@ -426,18 +426,14 @@ int phonet_route_del(struct net_device *dev, u8 daddr)
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return 0;
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}
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struct net_device *phonet_route_get(struct net *net, u8 daddr)
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struct net_device *phonet_route_get_rcu(struct net *net, u8 daddr)
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{
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struct phonet_net *pnn = phonet_pernet(net);
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struct phonet_routes *routes = &pnn->routes;
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struct net_device *dev;
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ASSERT_RTNL(); /* no need to hold the device */
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daddr >>= 2;
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rcu_read_lock();
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dev = rcu_dereference(routes->table[daddr]);
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rcu_read_unlock();
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return dev;
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}
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@ -264,10 +264,11 @@ static int route_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
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struct net *net = sock_net(skb->sk);
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u8 addr, addr_idx = 0, addr_start_idx = cb->args[0];
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rcu_read_lock();
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for (addr = 0; addr < 64; addr++) {
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struct net_device *dev;
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dev = phonet_route_get(net, addr << 2);
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dev = phonet_route_get_rcu(net, addr << 2);
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if (!dev)
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continue;
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@ -279,6 +280,7 @@ static int route_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
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}
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out:
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rcu_read_unlock();
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cb->args[0] = addr_idx;
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cb->args[1] = 0;
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