linux-stable/net/sched/sch_mqprio.c
Ahmed S. Darwish 29cbcd8582 net: sched: Remove Qdisc::running sequence counter
The Qdisc::running sequence counter has two uses:

  1. Reliably reading qdisc's tc statistics while the qdisc is running
     (a seqcount read/retry loop at gnet_stats_add_basic()).

  2. As a flag, indicating whether the qdisc in question is running
     (without any retry loops).

For the first usage, the Qdisc::running sequence counter write section,
qdisc_run_begin() => qdisc_run_end(), covers a much wider area than what
is actually needed: the raw qdisc's bstats update. A u64_stats sync
point was thus introduced (in previous commits) inside the bstats
structure itself. A local u64_stats write section is then started and
stopped for the bstats updates.

Use that u64_stats sync point mechanism for the bstats read/retry loop
at gnet_stats_add_basic().

For the second qdisc->running usage, a __QDISC_STATE_RUNNING bit flag,
accessed with atomic bitops, is sufficient. Using a bit flag instead of
a sequence counter at qdisc_run_begin/end() and qdisc_is_running() leads
to the SMP barriers implicitly added through raw_read_seqcount() and
write_seqcount_begin/end() getting removed. All call sites have been
surveyed though, and no required ordering was identified.

Now that the qdisc->running sequence counter is no longer used, remove
it.

Note, using u64_stats implies no sequence counter protection for 64-bit
architectures. This can lead to the qdisc tc statistics "packets" vs.
"bytes" values getting out of sync on rare occasions. The individual
values will still be valid.

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
2021-10-18 12:54:41 +01:00

625 lines
16 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* net/sched/sch_mqprio.c
*
* Copyright (c) 2010 John Fastabend <john.r.fastabend@intel.com>
*/
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <linux/module.h>
#include <net/netlink.h>
#include <net/pkt_sched.h>
#include <net/sch_generic.h>
#include <net/pkt_cls.h>
struct mqprio_sched {
struct Qdisc **qdiscs;
u16 mode;
u16 shaper;
int hw_offload;
u32 flags;
u64 min_rate[TC_QOPT_MAX_QUEUE];
u64 max_rate[TC_QOPT_MAX_QUEUE];
};
static void mqprio_destroy(struct Qdisc *sch)
{
struct net_device *dev = qdisc_dev(sch);
struct mqprio_sched *priv = qdisc_priv(sch);
unsigned int ntx;
if (priv->qdiscs) {
for (ntx = 0;
ntx < dev->num_tx_queues && priv->qdiscs[ntx];
ntx++)
qdisc_put(priv->qdiscs[ntx]);
kfree(priv->qdiscs);
}
if (priv->hw_offload && dev->netdev_ops->ndo_setup_tc) {
struct tc_mqprio_qopt_offload mqprio = { { 0 } };
switch (priv->mode) {
case TC_MQPRIO_MODE_DCB:
case TC_MQPRIO_MODE_CHANNEL:
dev->netdev_ops->ndo_setup_tc(dev,
TC_SETUP_QDISC_MQPRIO,
&mqprio);
break;
default:
return;
}
} else {
netdev_set_num_tc(dev, 0);
}
}
static int mqprio_parse_opt(struct net_device *dev, struct tc_mqprio_qopt *qopt)
{
int i, j;
/* Verify num_tc is not out of max range */
if (qopt->num_tc > TC_MAX_QUEUE)
return -EINVAL;
/* Verify priority mapping uses valid tcs */
for (i = 0; i < TC_BITMASK + 1; i++) {
if (qopt->prio_tc_map[i] >= qopt->num_tc)
return -EINVAL;
}
/* Limit qopt->hw to maximum supported offload value. Drivers have
* the option of overriding this later if they don't support the a
* given offload type.
*/
if (qopt->hw > TC_MQPRIO_HW_OFFLOAD_MAX)
qopt->hw = TC_MQPRIO_HW_OFFLOAD_MAX;
/* If hardware offload is requested we will leave it to the device
* to either populate the queue counts itself or to validate the
* provided queue counts. If ndo_setup_tc is not present then
* hardware doesn't support offload and we should return an error.
*/
if (qopt->hw)
return dev->netdev_ops->ndo_setup_tc ? 0 : -EINVAL;
for (i = 0; i < qopt->num_tc; i++) {
unsigned int last = qopt->offset[i] + qopt->count[i];
/* Verify the queue count is in tx range being equal to the
* real_num_tx_queues indicates the last queue is in use.
*/
if (qopt->offset[i] >= dev->real_num_tx_queues ||
!qopt->count[i] ||
last > dev->real_num_tx_queues)
return -EINVAL;
/* Verify that the offset and counts do not overlap */
for (j = i + 1; j < qopt->num_tc; j++) {
if (last > qopt->offset[j])
return -EINVAL;
}
}
return 0;
}
static const struct nla_policy mqprio_policy[TCA_MQPRIO_MAX + 1] = {
[TCA_MQPRIO_MODE] = { .len = sizeof(u16) },
[TCA_MQPRIO_SHAPER] = { .len = sizeof(u16) },
[TCA_MQPRIO_MIN_RATE64] = { .type = NLA_NESTED },
[TCA_MQPRIO_MAX_RATE64] = { .type = NLA_NESTED },
};
static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
const struct nla_policy *policy, int len)
{
int nested_len = nla_len(nla) - NLA_ALIGN(len);
if (nested_len >= nla_attr_size(0))
return nla_parse_deprecated(tb, maxtype,
nla_data(nla) + NLA_ALIGN(len),
nested_len, policy, NULL);
memset(tb, 0, sizeof(struct nlattr *) * (maxtype + 1));
return 0;
}
static int mqprio_init(struct Qdisc *sch, struct nlattr *opt,
struct netlink_ext_ack *extack)
{
struct net_device *dev = qdisc_dev(sch);
struct mqprio_sched *priv = qdisc_priv(sch);
struct netdev_queue *dev_queue;
struct Qdisc *qdisc;
int i, err = -EOPNOTSUPP;
struct tc_mqprio_qopt *qopt = NULL;
struct nlattr *tb[TCA_MQPRIO_MAX + 1];
struct nlattr *attr;
int rem;
int len;
BUILD_BUG_ON(TC_MAX_QUEUE != TC_QOPT_MAX_QUEUE);
BUILD_BUG_ON(TC_BITMASK != TC_QOPT_BITMASK);
if (sch->parent != TC_H_ROOT)
return -EOPNOTSUPP;
if (!netif_is_multiqueue(dev))
return -EOPNOTSUPP;
/* make certain can allocate enough classids to handle queues */
if (dev->num_tx_queues >= TC_H_MIN_PRIORITY)
return -ENOMEM;
if (!opt || nla_len(opt) < sizeof(*qopt))
return -EINVAL;
qopt = nla_data(opt);
if (mqprio_parse_opt(dev, qopt))
return -EINVAL;
len = nla_len(opt) - NLA_ALIGN(sizeof(*qopt));
if (len > 0) {
err = parse_attr(tb, TCA_MQPRIO_MAX, opt, mqprio_policy,
sizeof(*qopt));
if (err < 0)
return err;
if (!qopt->hw)
return -EINVAL;
if (tb[TCA_MQPRIO_MODE]) {
priv->flags |= TC_MQPRIO_F_MODE;
priv->mode = *(u16 *)nla_data(tb[TCA_MQPRIO_MODE]);
}
if (tb[TCA_MQPRIO_SHAPER]) {
priv->flags |= TC_MQPRIO_F_SHAPER;
priv->shaper = *(u16 *)nla_data(tb[TCA_MQPRIO_SHAPER]);
}
if (tb[TCA_MQPRIO_MIN_RATE64]) {
if (priv->shaper != TC_MQPRIO_SHAPER_BW_RATE)
return -EINVAL;
i = 0;
nla_for_each_nested(attr, tb[TCA_MQPRIO_MIN_RATE64],
rem) {
if (nla_type(attr) != TCA_MQPRIO_MIN_RATE64)
return -EINVAL;
if (i >= qopt->num_tc)
break;
priv->min_rate[i] = *(u64 *)nla_data(attr);
i++;
}
priv->flags |= TC_MQPRIO_F_MIN_RATE;
}
if (tb[TCA_MQPRIO_MAX_RATE64]) {
if (priv->shaper != TC_MQPRIO_SHAPER_BW_RATE)
return -EINVAL;
i = 0;
nla_for_each_nested(attr, tb[TCA_MQPRIO_MAX_RATE64],
rem) {
if (nla_type(attr) != TCA_MQPRIO_MAX_RATE64)
return -EINVAL;
if (i >= qopt->num_tc)
break;
priv->max_rate[i] = *(u64 *)nla_data(attr);
i++;
}
priv->flags |= TC_MQPRIO_F_MAX_RATE;
}
}
/* pre-allocate qdisc, attachment can't fail */
priv->qdiscs = kcalloc(dev->num_tx_queues, sizeof(priv->qdiscs[0]),
GFP_KERNEL);
if (!priv->qdiscs)
return -ENOMEM;
for (i = 0; i < dev->num_tx_queues; i++) {
dev_queue = netdev_get_tx_queue(dev, i);
qdisc = qdisc_create_dflt(dev_queue,
get_default_qdisc_ops(dev, i),
TC_H_MAKE(TC_H_MAJ(sch->handle),
TC_H_MIN(i + 1)), extack);
if (!qdisc)
return -ENOMEM;
priv->qdiscs[i] = qdisc;
qdisc->flags |= TCQ_F_ONETXQUEUE | TCQ_F_NOPARENT;
}
/* If the mqprio options indicate that hardware should own
* the queue mapping then run ndo_setup_tc otherwise use the
* supplied and verified mapping
*/
if (qopt->hw) {
struct tc_mqprio_qopt_offload mqprio = {.qopt = *qopt};
switch (priv->mode) {
case TC_MQPRIO_MODE_DCB:
if (priv->shaper != TC_MQPRIO_SHAPER_DCB)
return -EINVAL;
break;
case TC_MQPRIO_MODE_CHANNEL:
mqprio.flags = priv->flags;
if (priv->flags & TC_MQPRIO_F_MODE)
mqprio.mode = priv->mode;
if (priv->flags & TC_MQPRIO_F_SHAPER)
mqprio.shaper = priv->shaper;
if (priv->flags & TC_MQPRIO_F_MIN_RATE)
for (i = 0; i < mqprio.qopt.num_tc; i++)
mqprio.min_rate[i] = priv->min_rate[i];
if (priv->flags & TC_MQPRIO_F_MAX_RATE)
for (i = 0; i < mqprio.qopt.num_tc; i++)
mqprio.max_rate[i] = priv->max_rate[i];
break;
default:
return -EINVAL;
}
err = dev->netdev_ops->ndo_setup_tc(dev,
TC_SETUP_QDISC_MQPRIO,
&mqprio);
if (err)
return err;
priv->hw_offload = mqprio.qopt.hw;
} else {
netdev_set_num_tc(dev, qopt->num_tc);
for (i = 0; i < qopt->num_tc; i++)
netdev_set_tc_queue(dev, i,
qopt->count[i], qopt->offset[i]);
}
/* Always use supplied priority mappings */
for (i = 0; i < TC_BITMASK + 1; i++)
netdev_set_prio_tc_map(dev, i, qopt->prio_tc_map[i]);
sch->flags |= TCQ_F_MQROOT;
return 0;
}
static void mqprio_attach(struct Qdisc *sch)
{
struct net_device *dev = qdisc_dev(sch);
struct mqprio_sched *priv = qdisc_priv(sch);
struct Qdisc *qdisc, *old;
unsigned int ntx;
/* Attach underlying qdisc */
for (ntx = 0; ntx < dev->num_tx_queues; ntx++) {
qdisc = priv->qdiscs[ntx];
old = dev_graft_qdisc(qdisc->dev_queue, qdisc);
if (old)
qdisc_put(old);
if (ntx < dev->real_num_tx_queues)
qdisc_hash_add(qdisc, false);
}
kfree(priv->qdiscs);
priv->qdiscs = NULL;
}
static struct netdev_queue *mqprio_queue_get(struct Qdisc *sch,
unsigned long cl)
{
struct net_device *dev = qdisc_dev(sch);
unsigned long ntx = cl - 1;
if (ntx >= dev->num_tx_queues)
return NULL;
return netdev_get_tx_queue(dev, ntx);
}
static int mqprio_graft(struct Qdisc *sch, unsigned long cl, struct Qdisc *new,
struct Qdisc **old, struct netlink_ext_ack *extack)
{
struct net_device *dev = qdisc_dev(sch);
struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
if (!dev_queue)
return -EINVAL;
if (dev->flags & IFF_UP)
dev_deactivate(dev);
*old = dev_graft_qdisc(dev_queue, new);
if (new)
new->flags |= TCQ_F_ONETXQUEUE | TCQ_F_NOPARENT;
if (dev->flags & IFF_UP)
dev_activate(dev);
return 0;
}
static int dump_rates(struct mqprio_sched *priv,
struct tc_mqprio_qopt *opt, struct sk_buff *skb)
{
struct nlattr *nest;
int i;
if (priv->flags & TC_MQPRIO_F_MIN_RATE) {
nest = nla_nest_start_noflag(skb, TCA_MQPRIO_MIN_RATE64);
if (!nest)
goto nla_put_failure;
for (i = 0; i < opt->num_tc; i++) {
if (nla_put(skb, TCA_MQPRIO_MIN_RATE64,
sizeof(priv->min_rate[i]),
&priv->min_rate[i]))
goto nla_put_failure;
}
nla_nest_end(skb, nest);
}
if (priv->flags & TC_MQPRIO_F_MAX_RATE) {
nest = nla_nest_start_noflag(skb, TCA_MQPRIO_MAX_RATE64);
if (!nest)
goto nla_put_failure;
for (i = 0; i < opt->num_tc; i++) {
if (nla_put(skb, TCA_MQPRIO_MAX_RATE64,
sizeof(priv->max_rate[i]),
&priv->max_rate[i]))
goto nla_put_failure;
}
nla_nest_end(skb, nest);
}
return 0;
nla_put_failure:
nla_nest_cancel(skb, nest);
return -1;
}
static int mqprio_dump(struct Qdisc *sch, struct sk_buff *skb)
{
struct net_device *dev = qdisc_dev(sch);
struct mqprio_sched *priv = qdisc_priv(sch);
struct nlattr *nla = (struct nlattr *)skb_tail_pointer(skb);
struct tc_mqprio_qopt opt = { 0 };
struct Qdisc *qdisc;
unsigned int ntx, tc;
sch->q.qlen = 0;
gnet_stats_basic_sync_init(&sch->bstats);
memset(&sch->qstats, 0, sizeof(sch->qstats));
/* MQ supports lockless qdiscs. However, statistics accounting needs
* to account for all, none, or a mix of locked and unlocked child
* qdiscs. Percpu stats are added to counters in-band and locking
* qdisc totals are added at end.
*/
for (ntx = 0; ntx < dev->num_tx_queues; ntx++) {
qdisc = netdev_get_tx_queue(dev, ntx)->qdisc_sleeping;
spin_lock_bh(qdisc_lock(qdisc));
gnet_stats_add_basic(&sch->bstats, qdisc->cpu_bstats,
&qdisc->bstats, false);
gnet_stats_add_queue(&sch->qstats, qdisc->cpu_qstats,
&qdisc->qstats);
sch->q.qlen += qdisc_qlen(qdisc);
spin_unlock_bh(qdisc_lock(qdisc));
}
opt.num_tc = netdev_get_num_tc(dev);
memcpy(opt.prio_tc_map, dev->prio_tc_map, sizeof(opt.prio_tc_map));
opt.hw = priv->hw_offload;
for (tc = 0; tc < netdev_get_num_tc(dev); tc++) {
opt.count[tc] = dev->tc_to_txq[tc].count;
opt.offset[tc] = dev->tc_to_txq[tc].offset;
}
if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
goto nla_put_failure;
if ((priv->flags & TC_MQPRIO_F_MODE) &&
nla_put_u16(skb, TCA_MQPRIO_MODE, priv->mode))
goto nla_put_failure;
if ((priv->flags & TC_MQPRIO_F_SHAPER) &&
nla_put_u16(skb, TCA_MQPRIO_SHAPER, priv->shaper))
goto nla_put_failure;
if ((priv->flags & TC_MQPRIO_F_MIN_RATE ||
priv->flags & TC_MQPRIO_F_MAX_RATE) &&
(dump_rates(priv, &opt, skb) != 0))
goto nla_put_failure;
return nla_nest_end(skb, nla);
nla_put_failure:
nlmsg_trim(skb, nla);
return -1;
}
static struct Qdisc *mqprio_leaf(struct Qdisc *sch, unsigned long cl)
{
struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
if (!dev_queue)
return NULL;
return dev_queue->qdisc_sleeping;
}
static unsigned long mqprio_find(struct Qdisc *sch, u32 classid)
{
struct net_device *dev = qdisc_dev(sch);
unsigned int ntx = TC_H_MIN(classid);
/* There are essentially two regions here that have valid classid
* values. The first region will have a classid value of 1 through
* num_tx_queues. All of these are backed by actual Qdiscs.
*/
if (ntx < TC_H_MIN_PRIORITY)
return (ntx <= dev->num_tx_queues) ? ntx : 0;
/* The second region represents the hardware traffic classes. These
* are represented by classid values of TC_H_MIN_PRIORITY through
* TC_H_MIN_PRIORITY + netdev_get_num_tc - 1
*/
return ((ntx - TC_H_MIN_PRIORITY) < netdev_get_num_tc(dev)) ? ntx : 0;
}
static int mqprio_dump_class(struct Qdisc *sch, unsigned long cl,
struct sk_buff *skb, struct tcmsg *tcm)
{
if (cl < TC_H_MIN_PRIORITY) {
struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
struct net_device *dev = qdisc_dev(sch);
int tc = netdev_txq_to_tc(dev, cl - 1);
tcm->tcm_parent = (tc < 0) ? 0 :
TC_H_MAKE(TC_H_MAJ(sch->handle),
TC_H_MIN(tc + TC_H_MIN_PRIORITY));
tcm->tcm_info = dev_queue->qdisc_sleeping->handle;
} else {
tcm->tcm_parent = TC_H_ROOT;
tcm->tcm_info = 0;
}
tcm->tcm_handle |= TC_H_MIN(cl);
return 0;
}
static int mqprio_dump_class_stats(struct Qdisc *sch, unsigned long cl,
struct gnet_dump *d)
__releases(d->lock)
__acquires(d->lock)
{
if (cl >= TC_H_MIN_PRIORITY) {
int i;
__u32 qlen;
struct gnet_stats_queue qstats = {0};
struct gnet_stats_basic_sync bstats;
struct net_device *dev = qdisc_dev(sch);
struct netdev_tc_txq tc = dev->tc_to_txq[cl & TC_BITMASK];
gnet_stats_basic_sync_init(&bstats);
/* Drop lock here it will be reclaimed before touching
* statistics this is required because the d->lock we
* hold here is the look on dev_queue->qdisc_sleeping
* also acquired below.
*/
if (d->lock)
spin_unlock_bh(d->lock);
for (i = tc.offset; i < tc.offset + tc.count; i++) {
struct netdev_queue *q = netdev_get_tx_queue(dev, i);
struct Qdisc *qdisc = rtnl_dereference(q->qdisc);
spin_lock_bh(qdisc_lock(qdisc));
gnet_stats_add_basic(&bstats, qdisc->cpu_bstats,
&qdisc->bstats, false);
gnet_stats_add_queue(&qstats, qdisc->cpu_qstats,
&qdisc->qstats);
sch->q.qlen += qdisc_qlen(qdisc);
spin_unlock_bh(qdisc_lock(qdisc));
}
qlen = qdisc_qlen(sch) + qstats.qlen;
/* Reclaim root sleeping lock before completing stats */
if (d->lock)
spin_lock_bh(d->lock);
if (gnet_stats_copy_basic(d, NULL, &bstats, false) < 0 ||
gnet_stats_copy_queue(d, NULL, &qstats, qlen) < 0)
return -1;
} else {
struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
sch = dev_queue->qdisc_sleeping;
if (gnet_stats_copy_basic(d, sch->cpu_bstats,
&sch->bstats, true) < 0 ||
qdisc_qstats_copy(d, sch) < 0)
return -1;
}
return 0;
}
static void mqprio_walk(struct Qdisc *sch, struct qdisc_walker *arg)
{
struct net_device *dev = qdisc_dev(sch);
unsigned long ntx;
if (arg->stop)
return;
/* Walk hierarchy with a virtual class per tc */
arg->count = arg->skip;
for (ntx = arg->skip; ntx < netdev_get_num_tc(dev); ntx++) {
if (arg->fn(sch, ntx + TC_H_MIN_PRIORITY, arg) < 0) {
arg->stop = 1;
return;
}
arg->count++;
}
/* Pad the values and skip over unused traffic classes */
if (ntx < TC_MAX_QUEUE) {
arg->count = TC_MAX_QUEUE;
ntx = TC_MAX_QUEUE;
}
/* Reset offset, sort out remaining per-queue qdiscs */
for (ntx -= TC_MAX_QUEUE; ntx < dev->num_tx_queues; ntx++) {
if (arg->fn(sch, ntx + 1, arg) < 0) {
arg->stop = 1;
return;
}
arg->count++;
}
}
static struct netdev_queue *mqprio_select_queue(struct Qdisc *sch,
struct tcmsg *tcm)
{
return mqprio_queue_get(sch, TC_H_MIN(tcm->tcm_parent));
}
static const struct Qdisc_class_ops mqprio_class_ops = {
.graft = mqprio_graft,
.leaf = mqprio_leaf,
.find = mqprio_find,
.walk = mqprio_walk,
.dump = mqprio_dump_class,
.dump_stats = mqprio_dump_class_stats,
.select_queue = mqprio_select_queue,
};
static struct Qdisc_ops mqprio_qdisc_ops __read_mostly = {
.cl_ops = &mqprio_class_ops,
.id = "mqprio",
.priv_size = sizeof(struct mqprio_sched),
.init = mqprio_init,
.destroy = mqprio_destroy,
.attach = mqprio_attach,
.change_real_num_tx = mq_change_real_num_tx,
.dump = mqprio_dump,
.owner = THIS_MODULE,
};
static int __init mqprio_module_init(void)
{
return register_qdisc(&mqprio_qdisc_ops);
}
static void __exit mqprio_module_exit(void)
{
unregister_qdisc(&mqprio_qdisc_ops);
}
module_init(mqprio_module_init);
module_exit(mqprio_module_exit);
MODULE_LICENSE("GPL");