Commit eaa8097f authored Oct 07, 2021 by Sebastian Andrzej Siewior Committed by Greg Kroah-Hartman Oct 20, 2021

mqprio: Correct stats in mqprio_dump_class_stats().



commit 14132690860e4d06aa3e1c4d7d8e9866ba7756dd upstream.

Introduction of lockless subqueues broke the class statistics.
Before the change stats were accumulated in `bstats' and `qstats'
on the stack which was then copied to struct gnet_dump.

After the change the `bstats' and `qstats' are initialized to 0
and never updated, yet still fed to gnet_dump. The code updates
the global qdisc->cpu_bstats and qdisc->cpu_qstats instead,
clobbering them. Most likely a copy-paste error from the code in
mqprio_dump().

__gnet_stats_copy_basic() and __gnet_stats_copy_queue() accumulate
the values for per-CPU case but for global stats they overwrite
the value, so only stats from the last loop iteration / tc end up
in sch->[bq]stats.

Use the on-stack [bq]stats variables again and add the stats manually
in the global case.

Fixes: ce679e8d ("net: sched: add support for TCQ_F_NOLOCK subqueues to sch_mqprio")
Cc: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
https://lore.kernel.org/all/20211007175000.2334713-2-bigeasy@linutronix.de/


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 420824f4

net/sched/sch_mqprio.c

+18 −12

Original line number	Diff line number	Diff line
		@@ -531,22 +531,28 @@ static int mqprio_dump_class_stats(struct Qdisc *sch, unsigned long cl,
		for (i = tc.offset; i < tc.offset + tc.count; i++) {
		struct netdev_queue *q = netdev_get_tx_queue(dev, i);
		struct Qdisc *qdisc = rtnl_dereference(q->qdisc);
		struct gnet_stats_basic_cpu __percpu *cpu_bstats = NULL;
		struct gnet_stats_queue __percpu *cpu_qstats = NULL;

		spin_lock_bh(qdisc_lock(qdisc));
		if (qdisc_is_percpu_stats(qdisc)) {
		cpu_bstats = qdisc->cpu_bstats;
		cpu_qstats = qdisc->cpu_qstats;
		}

		if (qdisc_is_percpu_stats(qdisc)) {
		qlen = qdisc_qlen_sum(qdisc);
		__gnet_stats_copy_basic(NULL, &sch->bstats,
		cpu_bstats, &qdisc->bstats);
		__gnet_stats_copy_queue(&sch->qstats,
		cpu_qstats,

		__gnet_stats_copy_basic(NULL, &bstats,
		qdisc->cpu_bstats,
		&qdisc->bstats);
		__gnet_stats_copy_queue(&qstats,
		qdisc->cpu_qstats,
		&qdisc->qstats,
		qlen);
		} else {
		qlen += qdisc->q.qlen;
		bstats.bytes += qdisc->bstats.bytes;
		bstats.packets += qdisc->bstats.packets;
		qstats.backlog += qdisc->qstats.backlog;
		qstats.drops += qdisc->qstats.drops;
		qstats.requeues += qdisc->qstats.requeues;
		qstats.overlimits += qdisc->qstats.overlimits;
		}
		spin_unlock_bh(qdisc_lock(qdisc));
		}