[Devel] [PATCH RHEL9 COMMIT] net: dev: use kfree_skb_reason() for enqueue_to_backlog()

[Konstantin Khorenko]

The commit is pushed to "branch-rh9-5.14.0-162.6.1.vz9.18.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh9-5.14.0-162.6.1.vz9.18.2
------>
commit 460d13051081e9a31eccc58d06b6c5e0a8dd7922
Author: Menglong Dong <imagedong at tencent.com>
Date:   Tue Jan 3 17:39:20 2023 +0200

    net: dev: use kfree_skb_reason() for enqueue_to_backlog()
    
    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 needn't to make further distinctions.
    
    Signed-off-by: Menglong Dong <imagedong at tencent.com>
    Signed-off-by: David S. Miller <davem at davemloft.net>
    Acked-by: Nikolay Borisov <nborisov at suse.com>
    Signed-off-by: Nikolay Borisov <nikolay.borisov at virtuozzo.com>
    
    ======
    Patchset description:
    ms/net: Annotate skb free sites with reason
    
    This series backports most of the patches that add a reason to skb free sites.
    
    https://jira.sw.ru/browse/PSBM-143302
    
    Feature: net: improve verbosity of dropped packets reporting
---
 include/linux/skbuff.h     | 7 +++++++
 include/trace/events/skb.h | 1 +
 net/core/dev.c             | 5 ++++-
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 289f66cf58f9..e2cab7ab95d0 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -397,6 +397,13 @@ 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 ca65f2080724..4cc8be234073 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_TC_EGRESS, TC_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 9d7bc5812fae..07e7b913e825 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4555,10 +4555,12 @@ 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);
@@ -4581,13 +4583,14 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
 			napi_schedule_rps(sd);
 		goto enqueue;
 	}
+	reason = SKB_DROP_REASON_CPU_BACKLOG;
 
 drop:
 	sd->dropped++;
 	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;
 }