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net_sched: prio: insure proper transactional behavior 

Now prio_init() can return -ENOMEM, it also has to make sure
any allocated qdiscs are freed, since the caller (qdisc_create()) wont
call ->destroy() handler for us.

More generally, we want a transactional behavior for "tc qdisc
change ...", so prio_tune() should not make modifications if
any error is returned.

It means that we must validate parameters and allocate missing qdisc(s)
before taking root qdisc lock exactly once, to not leave the prio qdisc
in an intermediate state.

Fixes: cbdf451164 ("net_sched: prio: properly report out of memory errors")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2016-06-13 11:33:32 -07:00 committed by David S. Miller
parent 0c5ddb51e8
commit 3d7c8257d9
1 changed files with 24 additions and 35 deletions
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59
net/sched/sch_prio.c
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@ -172,8 +172,9 @@ prio_destroy(struct Qdisc *sch)
static int prio_tune(struct Qdisc *sch, struct nlattr *opt)
{
struct prio_sched_data *q = qdisc_priv(sch);
struct Qdisc *queues[TCQ_PRIO_BANDS];
int oldbands = q->bands, i;
struct tc_prio_qopt *qopt;
int i;
if (nla_len(opt) < sizeof(*qopt))
return -EINVAL;
@ -187,54 +188,42 @@ static int prio_tune(struct Qdisc *sch, struct nlattr *opt)
return -EINVAL;
}
/* Before commit, make sure we can allocate all new qdiscs */
for (i = oldbands; i < qopt->bands; i++) {
queues[i] = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
TC_H_MAKE(sch->handle, i + 1));
if (!queues[i]) {
while (i > oldbands)
qdisc_destroy(queues[--i]);
return -ENOMEM;
}
}
sch_tree_lock(sch);
q->bands = qopt->bands;
memcpy(q->prio2band, qopt->priomap, TC_PRIO_MAX+1);
for (i = q->bands; i < TCQ_PRIO_BANDS; i++) {
for (i = q->bands; i < oldbands; i++) {
struct Qdisc *child = q->queues[i];
q->queues[i] = &noop_qdisc;
if (child != &noop_qdisc) {
qdisc_tree_reduce_backlog(child, child->q.qlen, child->qstats.backlog);
qdisc_destroy(child);
}
qdisc_tree_reduce_backlog(child, child->q.qlen,
child->qstats.backlog);
qdisc_destroy(child);
}
for (i = oldbands; i < q->bands; i++)
q->queues[i] = queues[i];
sch_tree_unlock(sch);
for (i = 0; i < q->bands; i++) {
struct Qdisc *child;
if (q->queues[i] != &noop_qdisc)
continue;
child = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
TC_H_MAKE(sch->handle, i + 1));
if (!child)
return -ENOMEM;
sch_tree_lock(sch);
q->queues[i] = child;
sch_tree_unlock(sch);
}
return 0;
}
static int prio_init(struct Qdisc *sch, struct nlattr *opt)
{
struct prio_sched_data *q = qdisc_priv(sch);
int i;
for (i = 0; i < TCQ_PRIO_BANDS; i++)
q->queues[i] = &noop_qdisc;
if (opt == NULL) {
if (!opt)
return -EINVAL;
} else {
int err;
if ((err = prio_tune(sch, opt)) != 0)
return err;
}
return 0;
return prio_tune(sch, opt);
}
static int prio_dump(struct Qdisc *sch, struct sk_buff *skb)