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Commit cc106e44 authored by Yang Yingliang's avatar Yang Yingliang Committed by David S. Miller
Browse files

net: sched: tbf: fix the calculation of max_size 



Current max_size is caluated from rate table. Now, the rate table
has been replaced and it's wrong to caculate max_size based on this
rate table. It can lead wrong calculation of max_size.

The burst in kernel may be lower than user asked, because burst may gets
some loss when transform it to buffer(E.g. "burst 40kb rate 30mbit/s")
and it seems we cannot avoid this loss. Burst's value(max_size) based on
rate table may be equal user asked. If a packet's length is max_size, this
packet will be stalled in tbf_dequeue() because its length is above the
burst in kernel so that it cannot get enough tokens. The max_size guards
against enqueuing packet sizes above q->buffer "time" in tbf_enqueue().

To make consistent with the calculation of tokens, this patch add a helper
psched_ns_t2l() to calculate burst(max_size) directly to fix this problem.

After this fix, we can support to using 64bit rates to calculate burst as well.

Signed-off-by: default avatarYang Yingliang <yangyingliang@huawei.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4bd7b512

net/sched/sch_tbf.c

+70 −45
Original line number Diff line number Diff line
@@ -118,6 +118,30 @@ struct tbf_sched_data { 
};





/* Time to Length, convert time in ns to length in bytes

 * to determinate how many bytes can be sent in given time.

 */

static u64 psched_ns_t2l(const struct psched_ratecfg *r,

			 u64 time_in_ns)

{

	/* The formula is :

	 * len = (time_in_ns * r->rate_bytes_ps) / NSEC_PER_SEC

	 */

	u64 len = time_in_ns * r->rate_bytes_ps;



	do_div(len, NSEC_PER_SEC);



	if (unlikely(r->linklayer == TC_LINKLAYER_ATM))

		len = (len / 53) * 48;



	if (len > r->overhead)

		len -= r->overhead;

	else

		len = 0;



	return len;

}



/*

 * Return length of individual segments of a gso packet,

 * including all headers (MAC, IP, TCP/UDP)
@@ -289,10 +313,11 @@ static int tbf_change(struct Qdisc *sch, struct nlattr *opt) 
	struct tbf_sched_data *q = qdisc_priv(sch);

	struct nlattr *tb[TCA_TBF_MAX + 1];

	struct tc_tbf_qopt *qopt;

	struct qdisc_rate_table *rtab = NULL;

	struct qdisc_rate_table *ptab = NULL;

	struct Qdisc *child = NULL;

	int max_size, n;

	struct psched_ratecfg rate;

	struct psched_ratecfg peak;

	u64 max_size;

	s64 buffer, mtu;

	u64 rate64 = 0, prate64 = 0;



	err = nla_parse_nested(tb, TCA_TBF_MAX, opt, tbf_policy);
@@ -304,50 +329,58 @@ static int tbf_change(struct Qdisc *sch, struct nlattr *opt) 
		goto done;



	qopt = nla_data(tb[TCA_TBF_PARMS]);

	rtab = qdisc_get_rtab(&qopt->rate, tb[TCA_TBF_RTAB]);

	if (rtab == NULL)

	if (qopt->rate.linklayer == TC_LINKLAYER_UNAWARE)

		qdisc_put_rtab(qdisc_get_rtab(&qopt->rate,

					      tb[TCA_TBF_RTAB]));



	if (qopt->peakrate.linklayer == TC_LINKLAYER_UNAWARE)

			qdisc_put_rtab(qdisc_get_rtab(&qopt->peakrate,

						      tb[TCA_TBF_PTAB]));



	if (q->qdisc != &noop_qdisc) {

		err = fifo_set_limit(q->qdisc, qopt->limit);

		if (err)

			goto done;

	} else if (qopt->limit > 0) {

		child = fifo_create_dflt(sch, &bfifo_qdisc_ops, qopt->limit);

		if (IS_ERR(child)) {

			err = PTR_ERR(child);

			goto done;

		}

	}



	buffer = min_t(u64, PSCHED_TICKS2NS(qopt->buffer), ~0U);

	mtu = min_t(u64, PSCHED_TICKS2NS(qopt->mtu), ~0U);



	if (tb[TCA_TBF_RATE64])

		rate64 = nla_get_u64(tb[TCA_TBF_RATE64]);

	psched_ratecfg_precompute(&rate, &qopt->rate, rate64);



	max_size = min_t(u64, psched_ns_t2l(&rate, buffer), ~0U);



	if (qopt->peakrate.rate) {

		if (qopt->peakrate.rate > qopt->rate.rate)

			ptab = qdisc_get_rtab(&qopt->peakrate, tb[TCA_TBF_PTAB]);

		if (ptab == NULL)

		if (tb[TCA_TBF_PRATE64])

			prate64 = nla_get_u64(tb[TCA_TBF_PRATE64]);

		psched_ratecfg_precompute(&peak, &qopt->peakrate, prate64);

		if (peak.rate_bytes_ps <= rate.rate_bytes_ps) {

			pr_warn_ratelimited("sch_tbf: peakrate %llu is lower than or equals to rate %llu !\n",

					    peak.rate_bytes_ps, rate.rate_bytes_ps);

			err = -EINVAL;

			goto done;

		}



	for (n = 0; n < 256; n++)

		if (rtab->data[n] > qopt->buffer)

			break;

	max_size = (n << qopt->rate.cell_log) - 1;

	if (ptab) {

		int size;



		for (n = 0; n < 256; n++)

			if (ptab->data[n] > qopt->mtu)

				break;

		size = (n << qopt->peakrate.cell_log) - 1;

		if (size < max_size)

			max_size = size;

		max_size = min_t(u64, max_size, psched_ns_t2l(&peak, mtu));

	}

	if (max_size < 0)

		goto done;



	if (max_size < psched_mtu(qdisc_dev(sch)))

		pr_warn_ratelimited("sch_tbf: burst %u is lower than device %s mtu (%u) !\n",

		pr_warn_ratelimited("sch_tbf: burst %llu is lower than device %s mtu (%u) !\n",

				    max_size, qdisc_dev(sch)->name,

				    psched_mtu(qdisc_dev(sch)));



	if (q->qdisc != &noop_qdisc) {

		err = fifo_set_limit(q->qdisc, qopt->limit);

		if (err)

			goto done;

	} else if (qopt->limit > 0) {

		child = fifo_create_dflt(sch, &bfifo_qdisc_ops, qopt->limit);

		if (IS_ERR(child)) {

			err = PTR_ERR(child);

	if (!max_size) {

		err = -EINVAL;

		goto done;

	}

	}



	sch_tree_lock(sch);

	if (child) {
@@ -362,13 +395,9 @@ static int tbf_change(struct Qdisc *sch, struct nlattr *opt) 
	q->tokens = q->buffer;

	q->ptokens = q->mtu;



	if (tb[TCA_TBF_RATE64])

		rate64 = nla_get_u64(tb[TCA_TBF_RATE64]);

	psched_ratecfg_precompute(&q->rate, &rtab->rate, rate64);

	if (ptab) {

		if (tb[TCA_TBF_PRATE64])

			prate64 = nla_get_u64(tb[TCA_TBF_PRATE64]);

		psched_ratecfg_precompute(&q->peak, &ptab->rate, prate64);

	memcpy(&q->rate, &rate, sizeof(struct psched_ratecfg));

	if (qopt->peakrate.rate) {

		memcpy(&q->peak, &peak, sizeof(struct psched_ratecfg));

		q->peak_present = true;

	} else {

		q->peak_present = false;
@@ -377,10 +406,6 @@ static int tbf_change(struct Qdisc *sch, struct nlattr *opt) 
	sch_tree_unlock(sch);

	err = 0;

done:

	if (rtab)

		qdisc_put_rtab(rtab);

	if (ptab)

		qdisc_put_rtab(ptab);

	return err;

}