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

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

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.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@google.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);

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

[Eric Dumazet]

On Thu, 2018-02-22 at 19:36 -0800, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@google.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@google.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);

Oh I sent the wrong version of the patch, sorry.

Will send a V2.

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

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.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@google.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);
 

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

[David Miller]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Thu, 22 Feb 2018 19:45:27 -0800

> From: Eric Dumazet <edumazet@google.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@google.com>
> ---
> v2: Perform the zeroing in est_fetch_counters() instead of caller(s)

Applied and queued up for -stable.