netdev - [PATCH net-next 2/4] gen_stats: Add instead Set the value in __gnet_stats_copy

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Date:   Thu,  7 Oct 2021 19:49:58 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH net-next 2/4] gen_stats: Add instead Set the value in __gnet_stats_copy_basic().

Since day one __gnet_stats_copy_basic() always assigned the value to the
bstats argument overwriting the previous value.

Based on review there are five users of that function as of today:
- est_fetch_counters(), ___gnet_stats_copy_basic()
  memsets() bstats to zero, single invocation.

- mq_dump(), mqprio_dump(), mqprio_dump_class_stats()
  memsets() bstats to zero, multiple invocation but does not use the
  function due to !qdisc_is_percpu_stats().

It will probably simplify in percpu stats case if the value would be
added and not just stored.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 net/core/gen_stats.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/net/core/gen_stats.c b/net/core/gen_stats.c
index e491b083b3485..e12e544a7ab0f 100644
--- a/net/core/gen_stats.c
+++ b/net/core/gen_stats.c
@@ -143,6 +143,8 @@ __gnet_stats_copy_basic(const seqcount_t *running,
 			struct gnet_stats_basic_packed *b)
 {
 	unsigned int seq;
+	__u64 bytes = 0;
+	__u64 packets = 0;
 
 	if (cpu) {
 		__gnet_stats_copy_basic_cpu(bstats, cpu);
@@ -151,9 +153,12 @@ __gnet_stats_copy_basic(const seqcount_t *running,
 	do {
 		if (running)
 			seq = read_seqcount_begin(running);
-		bstats->bytes = b->bytes;
-		bstats->packets = b->packets;
+		bytes = b->bytes;
+		packets = b->packets;
 	} while (running && read_seqcount_retry(running, seq));
+
+	bstats->bytes += bytes;
+	bstats->packets += packets;
 }
 EXPORT_SYMBOL(__gnet_stats_copy_basic);
 
-- 
2.33.0