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Message-ID: <1473348943.15733.57.camel@edumazet-glaptop3.roam.corp.google.com>
Date: Thu, 08 Sep 2016 08:35:43 -0700
From: Eric Dumazet <eric.dumazet@...il.com>
To: David Miller <davem@...emloft.net>
Cc: Cong Wang <xiyou.wangcong@...il.com>, netdev@...r.kernel.org,
jhs@...atatu.com, John Fastabend <john.fastabend@...il.com>,
Hadar Hen Zion <hadarh@...lanox.com>,
Amir Vadai <amirva@...lanox.com>
Subject: [PATCH net] net_sched: act_mirred: full rcu conversion
From: Eric Dumazet <edumazet@...gle.com>
As reported by Cong Wang, I was lazy when I did initial RCU conversion
of tc_mirred, as I thought I could avoid allocation/freeing of a
parameter block.
Use an intermediate object so that fast path can get a consistent
snapshot of multiple variables (dev, action, eaction, ok_push)
Fixes: 2ee22a90c7af ("net_sched: act_mirred: remove spinlock in fast path")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: Cong Wang <xiyou.wangcong@...il.com>
Cc: John Fastabend <john.fastabend@...il.com>
Cc: Jamal Hadi Salim <jhs@...atatu.com>
Cc: Hadar Hen Zion <hadarh@...lanox.com>
Cc: Amir Vadai <amirva@...lanox.com>
---
include/net/tc_act/tc_mirred.h | 12 +++++-
net/sched/act_mirred.c | 54 +++++++++++++++++++++----------
2 files changed, 47 insertions(+), 19 deletions(-)
diff --git a/include/net/tc_act/tc_mirred.h b/include/net/tc_act/tc_mirred.h
index 62770add15bd..a613b4b9c56e 100644
--- a/include/net/tc_act/tc_mirred.h
+++ b/include/net/tc_act/tc_mirred.h
@@ -4,12 +4,20 @@
#include <net/act_api.h>
#include <linux/tc_act/tc_mirred.h>
+
+struct tcf_mirred_params {
+ struct net_device *dev;
+ int action;
+ int eaction;
+ int ok_push;
+ struct rcu_head rcu;
+};
+
struct tcf_mirred {
struct tc_action common;
int tcfm_eaction;
int tcfm_ifindex;
- int tcfm_ok_push;
- struct net_device __rcu *tcfm_dev;
+ struct tcf_mirred_params __rcu *params;
struct list_head tcfm_list;
};
#define to_mirred(a) ((struct tcf_mirred *)a)
diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
index 6038c85d92f5..1dc0b6036180 100644
--- a/net/sched/act_mirred.c
+++ b/net/sched/act_mirred.c
@@ -36,15 +36,16 @@ static DEFINE_SPINLOCK(mirred_list_lock);
static void tcf_mirred_release(struct tc_action *a, int bind)
{
struct tcf_mirred *m = to_mirred(a);
- struct net_device *dev;
+ struct tcf_mirred_params *params;
/* We could be called either in a RCU callback or with RTNL lock held. */
spin_lock_bh(&mirred_list_lock);
list_del(&m->tcfm_list);
- dev = rcu_dereference_protected(m->tcfm_dev, 1);
- if (dev)
- dev_put(dev);
+ params = rcu_dereference_protected(m->params, 1);
+ if (params->dev)
+ dev_put(params->dev);
spin_unlock_bh(&mirred_list_lock);
+ kfree_rcu(params, rcu);
}
static const struct nla_policy mirred_policy[TCA_MIRRED_MAX + 1] = {
@@ -60,6 +61,8 @@ static int tcf_mirred_init(struct net *net, struct nlattr *nla,
{
struct tc_action_net *tn = net_generic(net, mirred_net_id);
struct nlattr *tb[TCA_MIRRED_MAX + 1];
+ struct tcf_mirred_params *params_new;
+ struct tcf_mirred_params *params_old;
struct tc_mirred *parm;
struct tcf_mirred *m;
struct net_device *dev;
@@ -124,21 +127,33 @@ static int tcf_mirred_init(struct net *net, struct nlattr *nla,
tcf_hash_release(*a, bind);
if (!ovr)
return -EEXIST;
+ ret = 0;
}
m = to_mirred(*a);
ASSERT_RTNL();
- m->tcf_action = parm->action;
- m->tcfm_eaction = parm->eaction;
+ params_new = kzalloc(sizeof(*params_new), GFP_KERNEL);
+ if (unlikely(!params_new)) {
+ if (ret == ACT_P_CREATED)
+ tcf_hash_release(*a, bind);
+ return -ENOMEM;
+ }
+ params_old = rtnl_dereference(m->params);
+ params_new->action = m->tcf_action = parm->action;
+ params_new->eaction = m->tcfm_eaction = parm->eaction;
if (dev != NULL) {
m->tcfm_ifindex = parm->ifindex;
- if (ret != ACT_P_CREATED)
- dev_put(rcu_dereference_protected(m->tcfm_dev, 1));
dev_hold(dev);
- rcu_assign_pointer(m->tcfm_dev, dev);
- m->tcfm_ok_push = ok_push;
+ params_new->dev = dev;
+ params_new->ok_push = ok_push;
}
+ rcu_assign_pointer(m->params, params_new);
+ if (params_old) {
+ if (params_old->dev)
+ dev_put(params_old->dev);
+ kfree_rcu(params_old, rcu);
+ }
if (ret == ACT_P_CREATED) {
spin_lock_bh(&mirred_list_lock);
list_add(&m->tcfm_list, &mirred_list);
@@ -153,6 +168,7 @@ static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
struct tcf_result *res)
{
struct tcf_mirred *m = to_mirred(a);
+ struct tcf_mirred_params *params;
struct net_device *dev;
struct sk_buff *skb2;
int retval, err;
@@ -162,8 +178,9 @@ static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
bstats_cpu_update(this_cpu_ptr(m->common.cpu_bstats), skb);
rcu_read_lock();
- retval = READ_ONCE(m->tcf_action);
- dev = rcu_dereference(m->tcfm_dev);
+ params = rcu_dereference(m->params);
+ retval = params->action;
+ dev = params->dev;
if (unlikely(!dev)) {
pr_notice_once("tc mirred: target device is gone\n");
goto out;
@@ -181,12 +198,12 @@ static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
goto out;
if (!(at & AT_EGRESS)) {
- if (m->tcfm_ok_push)
+ if (params->ok_push)
skb_push_rcsum(skb2, skb->mac_len);
}
/* mirror is always swallowed */
- if (m->tcfm_eaction != TCA_EGRESS_MIRROR)
+ if (params->eaction != TCA_EGRESS_MIRROR)
skb2->tc_verd = SET_TC_FROM(skb2->tc_verd, at);
skb2->skb_iif = skb->dev->ifindex;
@@ -196,7 +213,7 @@ static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
if (err) {
out:
qstats_overlimit_inc(this_cpu_ptr(m->common.cpu_qstats));
- if (m->tcfm_eaction != TCA_EGRESS_MIRROR)
+ if (params->eaction != TCA_EGRESS_MIRROR)
retval = TC_ACT_SHOT;
}
rcu_read_unlock();
@@ -257,12 +274,15 @@ static int mirred_device_event(struct notifier_block *unused,
if (event == NETDEV_UNREGISTER) {
spin_lock_bh(&mirred_list_lock);
list_for_each_entry(m, &mirred_list, tcfm_list) {
- if (rcu_access_pointer(m->tcfm_dev) == dev) {
+ struct tcf_mirred_params *params;
+
+ params = rtnl_dereference(m->params);
+ if (params->dev == dev) {
dev_put(dev);
/* Note : no rcu grace period necessary, as
* net_device are already rcu protected.
*/
- RCU_INIT_POINTER(m->tcfm_dev, NULL);
+ params->dev = NULL;
}
}
spin_unlock_bh(&mirred_list_lock);
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