netdev - [PATCH net-next 2/4] net_sched: act_vlan: use RCU in tcf_vlan

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Message-ID: <20250827125349.3505302-3-edumazet@google.com>
Date: Wed, 27 Aug 2025 12:53:47 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, Jamal Hadi Salim <jhs@...atatu.com>, 
	Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 2/4] net_sched: act_vlan: use RCU in tcf_vlan_dump()

Also storing tcf_action into struct tcf_vlan_params
makes sure there is no discrepancy in tcf_vlan_act().

No longer block BH in tcf_vlan_init() when acquiring tcf_lock.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/tc_act/tc_vlan.h |  1 +
 net/sched/act_vlan.c         | 20 +++++++++-----------
 2 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/include/net/tc_act/tc_vlan.h b/include/net/tc_act/tc_vlan.h
index 3f5e9242b5e83d082b8a633b3702feadd5672b47..beadee41669a22d7519adaf348fb602cac7d273f 100644
--- a/include/net/tc_act/tc_vlan.h
+++ b/include/net/tc_act/tc_vlan.h
@@ -10,6 +10,7 @@
 #include <linux/tc_act/tc_vlan.h>
 
 struct tcf_vlan_params {
+	int		  action;
 	int               tcfv_action;
 	unsigned char     tcfv_push_dst[ETH_ALEN];
 	unsigned char     tcfv_push_src[ETH_ALEN];
diff --git a/net/sched/act_vlan.c b/net/sched/act_vlan.c
index 383bf18b6862f9a7a96087f1ed786fb869b70415..b46f980f3b2ae0bc50f1a37442945d281b7abddd 100644
--- a/net/sched/act_vlan.c
+++ b/net/sched/act_vlan.c
@@ -25,7 +25,6 @@ TC_INDIRECT_SCOPE int tcf_vlan_act(struct sk_buff *skb,
 {
 	struct tcf_vlan *v = to_vlan(a);
 	struct tcf_vlan_params *p;
-	int action;
 	int err;
 	u16 tci;
 
@@ -38,8 +37,6 @@ TC_INDIRECT_SCOPE int tcf_vlan_act(struct sk_buff *skb,
 	if (skb_at_tc_ingress(skb))
 		skb_push_rcsum(skb, skb->mac_len);
 
-	action = READ_ONCE(v->tcf_action);
-
 	p = rcu_dereference_bh(v->vlan_p);
 
 	switch (p->tcfv_action) {
@@ -97,7 +94,7 @@ TC_INDIRECT_SCOPE int tcf_vlan_act(struct sk_buff *skb,
 		skb_pull_rcsum(skb, skb->mac_len);
 
 	skb_reset_mac_len(skb);
-	return action;
+	return p->action;
 
 drop:
 	tcf_action_inc_drop_qstats(&v->common);
@@ -255,10 +252,11 @@ static int tcf_vlan_init(struct net *net, struct nlattr *nla,
 			   ETH_ALEN);
 	}
 
-	spin_lock_bh(&v->tcf_lock);
+	p->action = parm->action;
+	spin_lock(&v->tcf_lock);
 	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
 	p = rcu_replace_pointer(v->vlan_p, p, lockdep_is_held(&v->tcf_lock));
-	spin_unlock_bh(&v->tcf_lock);
+	spin_unlock(&v->tcf_lock);
 
 	if (goto_ch)
 		tcf_chain_put_by_act(goto_ch);
@@ -297,9 +295,9 @@ static int tcf_vlan_dump(struct sk_buff *skb, struct tc_action *a,
 	};
 	struct tcf_t t;
 
-	spin_lock_bh(&v->tcf_lock);
-	opt.action = v->tcf_action;
-	p = rcu_dereference_protected(v->vlan_p, lockdep_is_held(&v->tcf_lock));
+	rcu_read_lock();
+	p = rcu_dereference(v->vlan_p);
+	opt.action = p->action;
 	opt.v_action = p->tcfv_action;
 	if (nla_put(skb, TCA_VLAN_PARMS, sizeof(opt), &opt))
 		goto nla_put_failure;
@@ -325,12 +323,12 @@ static int tcf_vlan_dump(struct sk_buff *skb, struct tc_action *a,
 	tcf_tm_dump(&t, &v->tcf_tm);
 	if (nla_put_64bit(skb, TCA_VLAN_TM, sizeof(t), &t, TCA_VLAN_PAD))
 		goto nla_put_failure;
-	spin_unlock_bh(&v->tcf_lock);
+	rcu_read_unlock();
 
 	return skb->len;
 
 nla_put_failure:
-	spin_unlock_bh(&v->tcf_lock);
+	rcu_read_unlock();
 	nlmsg_trim(skb, b);
 	return -1;
 }
-- 
2.51.0.261.g7ce5a0a67e-goog