netdev - [PATCH net] net_sched: gen_estimator: fix broken estimators based on percpu stats

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Date:   Thu, 22 Feb 2018 19:36:14 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>
Subject: [PATCH net] net_sched: gen_estimator: fix broken estimators based
 on percpu stats

From: Eric Dumazet <edumazet@...gle.com>

pfifo_fast got percpu stats lately, uncovering a bug I introduced last
year in linux-4.10.

I missed the fact that we have to clear our temporary storage
before calling __gnet_stats_copy_basic() in the case of percpu stats.

Without this fix, rate estimators (tc qd replace dev xxx root est 1sec
4sec pfifo_fast) are utterly broken.

Fixes: 1c0d32fde5bd ("net_sched: gen_estimator: complete rewrite of rate estimators")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/core/gen_estimator.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/gen_estimator.c b/net/core/gen_estimator.c
index 0a3f88f08727f1f1217560407ff539c8a8c17496..f13ea3c1fa3eddc6be172df9eda8828da76045e7 100644
--- a/net/core/gen_estimator.c
+++ b/net/core/gen_estimator.c
@@ -79,7 +79,7 @@ static void est_fetch_counters(struct net_rate_estimator *e,
 static void est_timer(struct timer_list *t)
 {
 	struct net_rate_estimator *est = from_timer(est, t, timer);
-	struct gnet_stats_basic_packed b;
+	struct gnet_stats_basic_packed b = {0};
 	u64 rate, brate;
 
 	est_fetch_counters(est, &b);