netdev - [PATCH net-next] net_sched: act: remove tcfa

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Message-ID: <20250901093141.2093176-1-edumazet@google.com>
Date: Mon,  1 Sep 2025 09:31:41 +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] net_sched: act: remove tcfa_qstats

tcfa_qstats is currently only used to hold drops and overlimits counters.

tcf_action_inc_drop_qstats() and tcf_action_inc_overlimit_qstats()
currently acquire a->tcfa_lock to increment these counters.

Switch to two atomic_t to get lock-free accounting.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/act_api.h | 14 ++++++--------
 net/sched/act_api.c   | 12 ++++++++----
 2 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/include/net/act_api.h b/include/net/act_api.h
index 2894cfff2da3..91a24b5e0b93 100644
--- a/include/net/act_api.h
+++ b/include/net/act_api.h
@@ -33,7 +33,10 @@ struct tc_action {
 	struct tcf_t			tcfa_tm;
 	struct gnet_stats_basic_sync	tcfa_bstats;
 	struct gnet_stats_basic_sync	tcfa_bstats_hw;
-	struct gnet_stats_queue		tcfa_qstats;
+
+	atomic_t			tcfa_drops;
+	atomic_t			tcfa_overlimits;
+
 	struct net_rate_estimator __rcu *tcfa_rate_est;
 	spinlock_t			tcfa_lock;
 	struct gnet_stats_basic_sync __percpu *cpu_bstats;
@@ -53,7 +56,6 @@ struct tc_action {
 #define tcf_action	common.tcfa_action
 #define tcf_tm		common.tcfa_tm
 #define tcf_bstats	common.tcfa_bstats
-#define tcf_qstats	common.tcfa_qstats
 #define tcf_rate_est	common.tcfa_rate_est
 #define tcf_lock	common.tcfa_lock
 
@@ -241,9 +243,7 @@ static inline void tcf_action_inc_drop_qstats(struct tc_action *a)
 		qstats_drop_inc(this_cpu_ptr(a->cpu_qstats));
 		return;
 	}
-	spin_lock(&a->tcfa_lock);
-	qstats_drop_inc(&a->tcfa_qstats);
-	spin_unlock(&a->tcfa_lock);
+	atomic_inc(&a->tcfa_drops);
 }
 
 static inline void tcf_action_inc_overlimit_qstats(struct tc_action *a)
@@ -252,9 +252,7 @@ static inline void tcf_action_inc_overlimit_qstats(struct tc_action *a)
 		qstats_overlimit_inc(this_cpu_ptr(a->cpu_qstats));
 		return;
 	}
-	spin_lock(&a->tcfa_lock);
-	qstats_overlimit_inc(&a->tcfa_qstats);
-	spin_unlock(&a->tcfa_lock);
+	atomic_inc(&a->tcfa_overlimits);
 }
 
 void tcf_action_update_stats(struct tc_action *a, u64 bytes, u64 packets,
diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 9e468e463467..ff6be5cfe2b0 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -1585,7 +1585,7 @@ void tcf_action_update_stats(struct tc_action *a, u64 bytes, u64 packets,
 	}
 
 	_bstats_update(&a->tcfa_bstats, bytes, packets);
-	a->tcfa_qstats.drops += drops;
+	atomic_add(drops, &a->tcfa_drops);
 	if (hw)
 		_bstats_update(&a->tcfa_bstats_hw, bytes, packets);
 }
@@ -1594,8 +1594,9 @@ EXPORT_SYMBOL(tcf_action_update_stats);
 int tcf_action_copy_stats(struct sk_buff *skb, struct tc_action *p,
 			  int compat_mode)
 {
-	int err = 0;
+	struct gnet_stats_queue qstats = {0};
 	struct gnet_dump d;
+	int err = 0;
 
 	if (p == NULL)
 		goto errout;
@@ -1619,14 +1620,17 @@ int tcf_action_copy_stats(struct sk_buff *skb, struct tc_action *p,
 	if (err < 0)
 		goto errout;
 
+	qstats.drops = atomic_read(&p->tcfa_drops);
+	qstats.overlimits = atomic_read(&p->tcfa_overlimits);
+
 	if (gnet_stats_copy_basic(&d, p->cpu_bstats,
 				  &p->tcfa_bstats, false) < 0 ||
 	    gnet_stats_copy_basic_hw(&d, p->cpu_bstats_hw,
 				     &p->tcfa_bstats_hw, false) < 0 ||
 	    gnet_stats_copy_rate_est(&d, &p->tcfa_rate_est) < 0 ||
 	    gnet_stats_copy_queue(&d, p->cpu_qstats,
-				  &p->tcfa_qstats,
-				  p->tcfa_qstats.qlen) < 0)
+				  &qstats,
+				  qstats.qlen) < 0)
 		goto errout;
 
 	if (gnet_stats_finish_copy(&d) < 0)
-- 
2.51.0.318.gd7df087d1a-goog