From e67f88dd12f610da98ca838822f2c9b4e7c6100e Mon Sep 17 00:00:00 2001
From: Eric Dumazet <eric.dumazet@gmail.com>
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 <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>
---
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 13649eb57413d..8639de5750f64 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 134a2ff6b98bc..ffb0dc4cc0e80 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 8248ebb5891d0..3911586e12e4b 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 d7c4bb4b18208..2963312571954 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 0dcaa903e00e0..404fa15910274 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 dd88df0a5d7f8..4076a0b14b209 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 947038ddd04cb..47b3452675b67 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 58b3b1f991ed2..438accb7a5a8a 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;
--
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