[PATCH AUTOSEL 6.14 28/34] net_sched: sch_sfq: use a temporary work area for validating configuration

Sasha Levin
2025-04-14T13:27:16Z

From: Octavian Purdila <tavip@google.com>

[ Upstream commit 8c0cea59d40cf6dd13c2950437631dd614fbade6 ]

Many configuration parameters have influence on others (e.g. divisor
-> flows -> limit, depth -> limit) and so it is difficult to correctly
do all of the validation before applying the configuration. And if a
validation error is detected late it is difficult to roll back a
partially applied configuration.

To avoid these issues use a temporary work area to update and validate
the configuration and only then apply the configuration to the
internal state.

Signed-off-by: Octavian Purdila <tavip@google.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sched/sch_sfq.c | 56 +++++++++++++++++++++++++++++++++++----------
1 file changed, 44 insertions(+), 12 deletions(-)

diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
index 65d5b59da5830..7714ae94e0521 100644
--- a/net/sched/sch_sfq.c
+++ b/net/sched/sch_sfq.c
@@ -631,6 +631,15 @@ static int sfq_change(struct Qdisc *sch, struct nlattr *opt,
struct red_parms *p = NULL;
struct sk_buff *to_free = NULL;
struct sk_buff *tail = NULL;
+ unsigned int maxflows;
+ unsigned int quantum;
+ unsigned int divisor;
+ int perturb_period;
+ u8 headdrop;
+ u8 maxdepth;
+ int limit;
+ u8 flags;
+

if (opt->nla_len < nla_attr_size(sizeof(*ctl)))
return -EINVAL;
@@ -656,36 +665,59 @@ static int sfq_change(struct Qdisc *sch, struct nlattr *opt,
NL_SET_ERR_MSG_MOD(extack, "invalid limit");
return -EINVAL;
}
+
sch_tree_lock(sch);
+
+ limit = q->limit;
+ divisor = q->divisor;
+ headdrop = q->headdrop;
+ maxdepth = q->maxdepth;
+ maxflows = q->maxflows;
+ perturb_period = q->perturb_period;
+ quantum = q->quantum;
+ flags = q->flags;
+
+ /* update and validate configuration */
if (ctl->quantum)
- q->quantum = ctl->quantum;
- WRITE_ONCE(q->perturb_period, ctl->perturb_period * HZ);
+ quantum = ctl->quantum;
+ perturb_period = ctl->perturb_period * HZ;
if (ctl->flows)
- q->maxflows = min_t(u32, ctl->flows, SFQ_MAX_FLOWS);
+ maxflows = min_t(u32, ctl->flows, SFQ_MAX_FLOWS);
if (ctl->divisor) {
- q->divisor = ctl->divisor;
- q->maxflows = min_t(u32, q->maxflows, q->divisor);
+ divisor = ctl->divisor;
+ maxflows = min_t(u32, maxflows, divisor);
}
if (ctl_v1) {
if (ctl_v1->depth)
- q->maxdepth = min_t(u32, ctl_v1->depth, SFQ_MAX_DEPTH);
+ maxdepth = min_t(u32, ctl_v1->depth, SFQ_MAX_DEPTH);
if (p) {
- swap(q->red_parms, p);
- red_set_parms(q->red_parms,
+ red_set_parms(p,
ctl_v1->qth_min, ctl_v1->qth_max,
ctl_v1->Wlog,
ctl_v1->Plog, ctl_v1->Scell_log,
NULL,
ctl_v1->max_P);
}
- q->flags = ctl_v1->flags;
- q->headdrop = ctl_v1->headdrop;
+ flags = ctl_v1->flags;
+ headdrop = ctl_v1->headdrop;
}
if (ctl->limit) {
- q->limit = min_t(u32, ctl->limit, q->maxdepth * q->maxflows);
- q->maxflows = min_t(u32, q->maxflows, q->limit);
+ limit = min_t(u32, ctl->limit, maxdepth * maxflows);
+ maxflows = min_t(u32, maxflows, limit);
}

+ /* commit configuration */
+ q->limit = limit;
+ q->divisor = divisor;
+ q->headdrop = headdrop;
+ q->maxdepth = maxdepth;
+ q->maxflows = maxflows;
+ WRITE_ONCE(q->perturb_period, perturb_period);
+ q->quantum = quantum;
+ q->flags = flags;
+ if (p)
+ swap(q->red_parms, p);
+
qlen = sch->q.qlen;
while (sch->q.qlen > q->limit) {
dropped += sfq_drop(sch, &to_free);
--
2.39.5