[net PATCH v2] taprio: don't reject same mqprio settings

[net PATCH v2] taprio: don't reject same mqprio settings

[Ivan Khoronzhuk]

The taprio qdisc allows to set mqprio setting but only once. In case
if mqprio settings are provided next time the error is returned as
it's not allowed to change traffic class mapping in-flignt and that
is normal. But if configuration is absolutely the same - no need to
return error. It allows to provide same command couple times,
changing only base time for instance, or changing only scheds maps,
but leaving mqprio setting w/o modification. It more corresponds the
message: "Changing the traffic mapping of a running schedule is not
supported", so reject mqprio if it's really changed.

Also corrected TC_BITMASK + 1 for consistency, as proposed.

Fixes: a3d43c0d56f1 ("taprio: Add support adding an admin schedule")
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Tested-by: Vladimir Oltean <olteanv@gmail.com>
Acked-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
---

v2..v1:
- rebased on net/master instead of net-next/master
- added fixes tag
- corrected TC_BITMASK + 1 and used <=

 net/sched/sch_taprio.c | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 7cd68628c637..c609373c8661 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -922,7 +922,7 @@ static int taprio_parse_mqprio_opt(struct net_device *dev,
 	}
 
 	/* Verify priority mapping uses valid tcs */
-	for (i = 0; i < TC_BITMASK + 1; i++) {
+	for (i = 0; i <= TC_BITMASK; i++) {
 		if (qopt->prio_tc_map[i] >= qopt->num_tc) {
 			NL_SET_ERR_MSG(extack, "Invalid traffic class in priority to traffic class mapping");
 			return -EINVAL;
@@ -1347,6 +1347,26 @@ static int taprio_parse_clockid(struct Qdisc *sch, struct nlattr **tb,
 	return err;
 }
 
+static int taprio_mqprio_cmp(const struct net_device *dev,
+			     const struct tc_mqprio_qopt *mqprio)
+{
+	int i;
+
+	if (!mqprio || mqprio->num_tc != dev->num_tc)
+		return -1;
+
+	for (i = 0; i < mqprio->num_tc; i++)
+		if (dev->tc_to_txq[i].count != mqprio->count[i] ||
+		    dev->tc_to_txq[i].offset != mqprio->offset[i])
+			return -1;
+
+	for (i = 0; i <= TC_BITMASK; i++)
+		if (dev->prio_tc_map[i] != mqprio->prio_tc_map[i])
+			return -1;
+
+	return 0;
+}
+
 static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
 			 struct netlink_ext_ack *extack)
 {
@@ -1398,6 +1418,10 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
 	admin = rcu_dereference(q->admin_sched);
 	rcu_read_unlock();
 
+	/* no changes - no new mqprio settings */
+	if (!taprio_mqprio_cmp(dev, mqprio))
+		mqprio = NULL;
+
 	if (mqprio && (oper || admin)) {
 		NL_SET_ERR_MSG(extack, "Changing the traffic mapping of a running schedule is not supported");
 		err = -ENOTSUPP;
@@ -1455,7 +1479,7 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
 					    mqprio->offset[i]);
 
 		/* Always use supplied priority mappings */
-		for (i = 0; i < TC_BITMASK + 1; i++)
+		for (i = 0; i <= TC_BITMASK; i++)
 			netdev_set_prio_tc_map(dev, i,
 					       mqprio->prio_tc_map[i]);
 	}
-- 
2.20.1

Re: [net PATCH v2] taprio: don't reject same mqprio settings

[David Miller]

From: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Date: Tue, 19 Nov 2019 02:23:12 +0200

> The taprio qdisc allows to set mqprio setting but only once. In case
> if mqprio settings are provided next time the error is returned as
> it's not allowed to change traffic class mapping in-flignt and that
> is normal. But if configuration is absolutely the same - no need to
> return error. It allows to provide same command couple times,
> changing only base time for instance, or changing only scheds maps,
> but leaving mqprio setting w/o modification. It more corresponds the
> message: "Changing the traffic mapping of a running schedule is not
> supported", so reject mqprio if it's really changed.
> 
> Also corrected TC_BITMASK + 1 for consistency, as proposed.
> 
> Fixes: a3d43c0d56f1 ("taprio: Add support adding an admin schedule")
> Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
> Tested-by: Vladimir Oltean <olteanv@gmail.com>
> Acked-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>

Applied and queued up for -stable.