From e67f88dd12f610da98ca838822f2c9b4e7c6100e Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 27 Apr 2011 22:56:07 +0000 Subject: [PATCH] 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 : 1c2d670f366 : [RTNETLINK]: Hold rtnl_mutex during netlink dump callbacks 6313c1e0992 : [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 Cc: Patrick McHardy Cc: Remi Denis-Courmont Acked-by: Stephen Hemminger Signed-off-by: David S. Miller --- include/net/phonet/pn_dev.h | 2 +- net/bridge/br_netlink.c | 7 ++++--- net/core/fib_rules.c | 3 ++- net/core/rtnetlink.c | 12 +++++------- net/decnet/dn_dev.c | 10 ++++++---- net/ipv6/ip6_fib.c | 4 +++- net/phonet/pn_dev.c | 6 +----- net/phonet/pn_netlink.c | 4 +++- 8 files changed, 25 insertions(+), 23 deletions(-) diff --git a/include/net/phonet/pn_dev.h b/include/net/phonet/pn_dev.h index 13649eb57413..8639de5750f6 100644 --- a/include/net/phonet/pn_dev.h +++ b/include/net/phonet/pn_dev.h @@ -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 diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c index 134a2ff6b98b..ffb0dc4cc0e8 100644 --- a/net/bridge/br_netlink.c +++ b/net/bridge/br_netlink.c @@ -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; diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c index 8248ebb5891d..3911586e12e4 100644 --- a/net/core/fib_rules.c +++ b/net/core/fib_rules.c @@ -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; diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index d7c4bb4b1820..296331257195 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -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 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb) } } 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; diff --git a/net/decnet/dn_dev.c b/net/decnet/dn_dev.c index 0dcaa903e00e..404fa1591027 100644 --- a/net/decnet/dn_dev.c +++ b/net/decnet/dn_dev.c @@ -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 @@ static int dn_nl_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb) idx++; } done: + rcu_read_unlock(); cb->args[0] = idx; cb->args[1] = dn_idx; diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c index dd88df0a5d7f..4076a0b14b20 100644 --- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -394,10 +394,11 @@ static int inet6_dump_fib(struct sk_buff *skb, struct netlink_callback *cb) arg.net = net; w->args = &arg; + rcu_read_lock(); for (h = s_h; h < FIB6_TABLE_HASHSZ; h++, s_e = 0) { e = 0; head = &net->ipv6.fib_table_hash[h]; - hlist_for_each_entry(tb, node, head, tb6_hlist) { + hlist_for_each_entry_rcu(tb, node, head, tb6_hlist) { if (e < s_e) goto next; res = fib6_dump_table(tb, skb, cb); @@ -408,6 +409,7 @@ static int inet6_dump_fib(struct sk_buff *skb, struct netlink_callback *cb) } } out: + rcu_read_unlock(); cb->args[1] = e; cb->args[0] = h; diff --git a/net/phonet/pn_dev.c b/net/phonet/pn_dev.c index 947038ddd04c..47b3452675b6 100644 --- a/net/phonet/pn_dev.c +++ b/net/phonet/pn_dev.c @@ -426,18 +426,14 @@ int phonet_route_del(struct net_device *dev, u8 daddr) return 0; } -struct net_device *phonet_route_get(struct net *net, u8 daddr) +struct net_device *phonet_route_get_rcu(struct net *net, u8 daddr) { struct phonet_net *pnn = phonet_pernet(net); struct phonet_routes *routes = &pnn->routes; struct net_device *dev; - ASSERT_RTNL(); /* no need to hold the device */ - daddr >>= 2; - rcu_read_lock(); dev = rcu_dereference(routes->table[daddr]); - rcu_read_unlock(); return dev; } diff --git a/net/phonet/pn_netlink.c b/net/phonet/pn_netlink.c index 58b3b1f991ed..438accb7a5a8 100644 --- a/net/phonet/pn_netlink.c +++ b/net/phonet/pn_netlink.c @@ -264,10 +264,11 @@ static int route_dumpit(struct sk_buff *skb, struct netlink_callback *cb) struct net *net = sock_net(skb->sk); u8 addr, addr_idx = 0, addr_start_idx = cb->args[0]; + rcu_read_lock(); for (addr = 0; addr < 64; addr++) { struct net_device *dev; - dev = phonet_route_get(net, addr << 2); + dev = phonet_route_get_rcu(net, addr << 2); if (!dev) continue; @@ -279,6 +280,7 @@ static int route_dumpit(struct sk_buff *skb, struct netlink_callback *cb) } out: + rcu_read_unlock(); cb->args[0] = addr_idx; cb->args[1] = 0; -- GitLab