netdev - [PATCH v2 net] net_sched: gen_estimator: fix broken estimators based on percpu stats

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Date:   Thu, 22 Feb 2018 19:45:27 -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 v2 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>
---
v2: Perform the zeroing in est_fetch_counters() instead of caller(s)

 net/core/gen_estimator.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/net/core/gen_estimator.c b/net/core/gen_estimator.c
index 0a3f88f08727f1f1217560407ff539c8a8c17496..98fd12721221e4aa26e4d11be9de6c0305fb6dd9 100644
--- a/net/core/gen_estimator.c
+++ b/net/core/gen_estimator.c
@@ -66,6 +66,7 @@ struct net_rate_estimator {
 static void est_fetch_counters(struct net_rate_estimator *e,
 			       struct gnet_stats_basic_packed *b)
 {
+	memset(b, 0, sizeof(*b));
 	if (e->stats_lock)
 		spin_lock(e->stats_lock);