sch_fifo.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * net/sched/sch_fifo.c	The simplest FIFO queue.
  4 *
  5 * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
  6 */
  7
  8#include <linux/module.h>
  9#include <linux/slab.h>
 10#include <linux/types.h>
 11#include <linux/kernel.h>
 12#include <linux/errno.h>
 13#include <linux/skbuff.h>
 14#include <net/pkt_sched.h>
 15#include <net/pkt_cls.h>
 16
 17/* 1 band FIFO pseudo-"scheduler" */
 18
 19static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 20			 struct sk_buff **to_free)
 21{
 22	if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <=
 23		   READ_ONCE(sch->limit)))
 24		return qdisc_enqueue_tail(skb, sch);
 25
 26	return qdisc_drop(skb, sch, to_free);
 27}
 28
 29static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 30			 struct sk_buff **to_free)
 31{
 32	if (likely(sch->q.qlen < READ_ONCE(sch->limit)))
 33		return qdisc_enqueue_tail(skb, sch);
 34
 35	return qdisc_drop(skb, sch, to_free);
 36}
 37
 38static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 39			      struct sk_buff **to_free)
 40{
 41	unsigned int prev_backlog;
 42
 43	if (unlikely(READ_ONCE(sch->limit) == 0))
 44		return qdisc_drop(skb, sch, to_free);
 45
 46	if (likely(sch->q.qlen < READ_ONCE(sch->limit)))
 47		return qdisc_enqueue_tail(skb, sch);
 48
 49	prev_backlog = sch->qstats.backlog;
 50	/* queue full, remove one skb to fulfill the limit */
 51	__qdisc_queue_drop_head(sch, &sch->q, to_free);
 52	qdisc_qstats_drop(sch);
 53	qdisc_enqueue_tail(skb, sch);
 54
 55	qdisc_tree_reduce_backlog(sch, 0, prev_backlog - sch->qstats.backlog);
 56	return NET_XMIT_CN;
 57}
 58
 59static void fifo_offload_init(struct Qdisc *sch)
 60{
 61	struct net_device *dev = qdisc_dev(sch);
 62	struct tc_fifo_qopt_offload qopt;
 63
 64	if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
 65		return;
 66
 67	qopt.command = TC_FIFO_REPLACE;
 68	qopt.handle = sch->handle;
 69	qopt.parent = sch->parent;
 70	dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_FIFO, &qopt);
 71}
 72
 73static void fifo_offload_destroy(struct Qdisc *sch)
 74{
 75	struct net_device *dev = qdisc_dev(sch);
 76	struct tc_fifo_qopt_offload qopt;
 77
 78	if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
 79		return;
 80
 81	qopt.command = TC_FIFO_DESTROY;
 82	qopt.handle = sch->handle;
 83	qopt.parent = sch->parent;
 84	dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_FIFO, &qopt);
 85}
 86
 87static int fifo_offload_dump(struct Qdisc *sch)
 88{
 89	struct tc_fifo_qopt_offload qopt;
 90
 91	qopt.command = TC_FIFO_STATS;
 92	qopt.handle = sch->handle;
 93	qopt.parent = sch->parent;
 94	qopt.stats.bstats = &sch->bstats;
 95	qopt.stats.qstats = &sch->qstats;
 96
 97	return qdisc_offload_dump_helper(sch, TC_SETUP_QDISC_FIFO, &qopt);
 98}
 99
100static int __fifo_init(struct Qdisc *sch, struct nlattr *opt,
101		       struct netlink_ext_ack *extack)
102{
103	bool bypass;
104	bool is_bfifo = sch->ops == &bfifo_qdisc_ops;
105
106	if (opt == NULL) {
107		u32 limit = qdisc_dev(sch)->tx_queue_len;
108
109		if (is_bfifo)
110			limit *= psched_mtu(qdisc_dev(sch));
111
112		WRITE_ONCE(sch->limit, limit);
113	} else {
114		struct tc_fifo_qopt *ctl = nla_data(opt);
115
116		if (nla_len(opt) < sizeof(*ctl))
117			return -EINVAL;
118
119		WRITE_ONCE(sch->limit, ctl->limit);
120	}
121
122	if (is_bfifo)
123		bypass = sch->limit >= psched_mtu(qdisc_dev(sch));
124	else
125		bypass = sch->limit >= 1;
126
127	if (bypass)
128		sch->flags |= TCQ_F_CAN_BYPASS;
129	else
130		sch->flags &= ~TCQ_F_CAN_BYPASS;
131
132	return 0;
133}
134
135static int fifo_init(struct Qdisc *sch, struct nlattr *opt,
136		     struct netlink_ext_ack *extack)
137{
138	int err;
139
140	err = __fifo_init(sch, opt, extack);
141	if (err)
142		return err;
143
144	fifo_offload_init(sch);
145	return 0;
146}
147
148static int fifo_hd_init(struct Qdisc *sch, struct nlattr *opt,
149			struct netlink_ext_ack *extack)
150{
151	return __fifo_init(sch, opt, extack);
152}
153
154static void fifo_destroy(struct Qdisc *sch)
155{
156	fifo_offload_destroy(sch);
157}
158
159static int __fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
160{
161	struct tc_fifo_qopt opt = { .limit = READ_ONCE(sch->limit) };
162
163	if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
164		goto nla_put_failure;
165	return skb->len;
166
167nla_put_failure:
168	return -1;
169}
170
171static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
172{
173	int err;
174
175	err = fifo_offload_dump(sch);
176	if (err)
177		return err;
178
179	return __fifo_dump(sch, skb);
180}
181
182static int fifo_hd_dump(struct Qdisc *sch, struct sk_buff *skb)
183{
184	return __fifo_dump(sch, skb);
185}
186
187struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
188	.id		=	"pfifo",
189	.priv_size	=	0,
190	.enqueue	=	pfifo_enqueue,
191	.dequeue	=	qdisc_dequeue_head,
192	.peek		=	qdisc_peek_head,
193	.init		=	fifo_init,
194	.destroy	=	fifo_destroy,
195	.reset		=	qdisc_reset_queue,
196	.change		=	fifo_init,
197	.dump		=	fifo_dump,
198	.owner		=	THIS_MODULE,
199};
200EXPORT_SYMBOL(pfifo_qdisc_ops);
201
202struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
203	.id		=	"bfifo",
204	.priv_size	=	0,
205	.enqueue	=	bfifo_enqueue,
206	.dequeue	=	qdisc_dequeue_head,
207	.peek		=	qdisc_peek_head,
208	.init		=	fifo_init,
209	.destroy	=	fifo_destroy,
210	.reset		=	qdisc_reset_queue,
211	.change		=	fifo_init,
212	.dump		=	fifo_dump,
213	.owner		=	THIS_MODULE,
214};
215EXPORT_SYMBOL(bfifo_qdisc_ops);
216
217struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
218	.id		=	"pfifo_head_drop",
219	.priv_size	=	0,
220	.enqueue	=	pfifo_tail_enqueue,
221	.dequeue	=	qdisc_dequeue_head,
222	.peek		=	qdisc_peek_head,
223	.init		=	fifo_hd_init,
224	.reset		=	qdisc_reset_queue,
225	.change		=	fifo_hd_init,
226	.dump		=	fifo_hd_dump,
227	.owner		=	THIS_MODULE,
228};
229
230/* Pass size change message down to embedded FIFO */
231int fifo_set_limit(struct Qdisc *q, unsigned int limit)
232{
233	struct nlattr *nla;
234	int ret = -ENOMEM;
235
236	/* Hack to avoid sending change message to non-FIFO */
237	if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
238		return 0;
239
240	if (!q->ops->change)
241		return 0;
242
243	nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
244	if (nla) {
245		nla->nla_type = RTM_NEWQDISC;
246		nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
247		((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
248
249		ret = q->ops->change(q, nla, NULL);
250		kfree(nla);
251	}
252	return ret;
253}
254EXPORT_SYMBOL(fifo_set_limit);
255
256struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
257			       unsigned int limit,
258			       struct netlink_ext_ack *extack)
259{
260	struct Qdisc *q;
261	int err = -ENOMEM;
262
263	q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1),
264			      extack);
265	if (q) {
266		err = fifo_set_limit(q, limit);
267		if (err < 0) {
268			qdisc_put(q);
269			q = NULL;
270		}
271	}
272
273	return q ? : ERR_PTR(err);
274}
275EXPORT_SYMBOL(fifo_create_dflt);
276MODULE_DESCRIPTION("Single queue packet and byte based First In First Out(P/BFIFO) scheduler");