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net/sched: make stab available before ops->init() call 

Some qdiscs like taprio turn out to be actually pretty reliant on a well
configured stab, to not underestimate the skb transmission time (by
properly accounting for L1 overhead).

In a future change, taprio will need the stab, if configured by the
user, to be available at ops->init() time. It will become even more
important in upcoming work, when the overhead will be used for the
queueMaxSDU calculation that is passed to an offloading driver.

However, rcu_assign_pointer(sch->stab, stab) is called right after
ops->init(), making it unavailable, and I don't really see a good reason
for that.

Move it earlier, which nicely seems to simplify the error handling path
as well.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Kurt Kanzenbach <kurt@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Vladimir Oltean 2023-02-07 15:54:35 +02:00 committed by David S. Miller
parent a1e6ad30fa
commit 1f62879e36
1 changed files with 11 additions and 18 deletions
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29
net/sched/sch_api.c
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@ -1282,12 +1282,6 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
if (err)
goto err_out3;
if (ops->init) {
err = ops->init(sch, tca[TCA_OPTIONS], extack);
if (err != 0)
goto err_out5;
}
if (tca[TCA_STAB]) {
stab = qdisc_get_stab(tca[TCA_STAB], extack);
if (IS_ERR(stab)) {
@ -1296,11 +1290,18 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
}
rcu_assign_pointer(sch->stab, stab);
}
if (ops->init) {
err = ops->init(sch, tca[TCA_OPTIONS], extack);
if (err != 0)
goto err_out5;
}
if (tca[TCA_RATE]) {
err = -EOPNOTSUPP;
if (sch->flags & TCQ_F_MQROOT) {
NL_SET_ERR_MSG(extack, "Cannot attach rate estimator to a multi-queue root qdisc");
goto err_out4;
goto err_out5;
}
err = gen_new_estimator(&sch->bstats,
@ -1311,7 +1312,7 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
tca[TCA_RATE]);
if (err) {
NL_SET_ERR_MSG(extack, "Failed to generate new estimator");
goto err_out4;
goto err_out5;
}
}
@ -1321,6 +1322,8 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
return sch;
err_out5:
qdisc_put_stab(rtnl_dereference(sch->stab));
err_out4:
/* ops->init() failed, we call ->destroy() like qdisc_create_dflt() */
if (ops->destroy)
ops->destroy(sch);
@ -1332,16 +1335,6 @@ err_out2:
err_out:
*errp = err;
return NULL;
err_out4:
/*
* Any broken qdiscs that would require a ops->reset() here?
* The qdisc was never in action so it shouldn't be necessary.
*/
qdisc_put_stab(rtnl_dereference(sch->stab));
if (ops->destroy)
ops->destroy(sch);
goto err_out3;
}
static int qdisc_change(struct Qdisc *sch, struct nlattr **tca,