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Subject: [PATCH net-next 4/7] net: dev: use kfree_skb_reason() for enqueue_to_backlog()
Date:   Fri,  4 Mar 2022 01:47:04 +0800
Message-Id: <20220303174707.40431-5-imagedong@tencent.com>
In-Reply-To: <20220303174707.40431-1-imagedong@tencent.com>
References: <20220303174707.40431-1-imagedong@tencent.com>
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From: Menglong Dong <imagedong@tencent.com>

Replace kfree_skb() used in enqueue_to_backlog() with
kfree_skb_reason(). The skb rop reason SKB_DROP_REASON_CPU_BACKLOG is
introduced for the case of failing to enqueue the skb to the per CPU
backlog queue. The further reason can be backlog queue full or RPS
flow limition, and I think we meedn't to make further distinctions.

Signed-off-by: Menglong Dong <imagedong@tencent.com>
---
 include/linux/skbuff.h     | 6 ++++++
 include/trace/events/skb.h | 1 +
 net/core/dev.c             | 6 +++++-
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 62f9d15ec6ec..d2cf87ff84c2 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -402,6 +402,12 @@ enum skb_drop_reason {
 					 * outputting (failed to enqueue to
 					 * current qdisc)
 					 */
+	SKB_DROP_REASON_CPU_BACKLOG,	/* failed to enqueue the skb to
+					 * the per CPU backlog queue. This
+					 * can be caused by backlog queue
+					 * full (see netdev_max_backlog in
+					 * net.rst) or RPS flow limit
+					 */
 	SKB_DROP_REASON_MAX,
 };
 
diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index 80fe15d175e3..29c360b5e114 100644
--- a/include/trace/events/skb.h
+++ b/include/trace/events/skb.h
@@ -47,6 +47,7 @@
 	EM(SKB_DROP_REASON_NEIGH_DEAD, NEIGH_DEAD)		\
 	EM(SKB_DROP_REASON_QDISC_EGRESS, QDISC_EGRESS)		\
 	EM(SKB_DROP_REASON_QDISC_DROP, QDISC_DROP)		\
+	EM(SKB_DROP_REASON_CPU_BACKLOG, CPU_BACKLOG)		\
 	EMe(SKB_DROP_REASON_MAX, MAX)
 
 #undef EM
diff --git a/net/core/dev.c b/net/core/dev.c
index 3280ba2502cd..373fa7a33ffa 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4541,10 +4541,12 @@ static bool skb_flow_limit(struct sk_buff *skb, unsigned int qlen)
 static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
 			      unsigned int *qtail)
 {
+	enum skb_drop_reason reason;
 	struct softnet_data *sd;
 	unsigned long flags;
 	unsigned int qlen;
 
+	reason = SKB_DROP_REASON_NOT_SPECIFIED;
 	sd = &per_cpu(softnet_data, cpu);
 
 	rps_lock_irqsave(sd, &flags);
@@ -4566,6 +4568,8 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
 		if (!__test_and_set_bit(NAPI_STATE_SCHED, &sd->backlog.state))
 			napi_schedule_rps(sd);
 		goto enqueue;
+	} else {
+		reason = SKB_DROP_REASON_CPU_BACKLOG;
 	}
 
 drop:
@@ -4573,7 +4577,7 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
 	rps_unlock_irq_restore(sd, &flags);
 
 	atomic_long_inc(&skb->dev->rx_dropped);
-	kfree_skb(skb);
+	kfree_skb_reason(skb, reason);
 	return NET_RX_DROP;
 }
 
-- 
2.35.1