1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * net/sched/sch_fifo.c The simplest FIFO queue.
5 * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
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>
16 /* 1 band FIFO pseudo-"scheduler" */
18 static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
19 struct sk_buff **to_free)
21 if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit))
22 return qdisc_enqueue_tail(skb, sch);
24 return qdisc_drop(skb, sch, to_free);
27 static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
28 struct sk_buff **to_free)
30 if (likely(sch->q.qlen < sch->limit))
31 return qdisc_enqueue_tail(skb, sch);
33 return qdisc_drop(skb, sch, to_free);
36 static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch,
37 struct sk_buff **to_free)
39 unsigned int prev_backlog;
41 if (likely(sch->q.qlen < sch->limit))
42 return qdisc_enqueue_tail(skb, sch);
44 prev_backlog = sch->qstats.backlog;
45 /* queue full, remove one skb to fulfill the limit */
46 __qdisc_queue_drop_head(sch, &sch->q, to_free);
47 qdisc_qstats_drop(sch);
48 qdisc_enqueue_tail(skb, sch);
50 qdisc_tree_reduce_backlog(sch, 0, prev_backlog - sch->qstats.backlog);
54 static int fifo_init(struct Qdisc *sch, struct nlattr *opt,
55 struct netlink_ext_ack *extack)
58 bool is_bfifo = sch->ops == &bfifo_qdisc_ops;
61 u32 limit = qdisc_dev(sch)->tx_queue_len;
64 limit *= psched_mtu(qdisc_dev(sch));
68 struct tc_fifo_qopt *ctl = nla_data(opt);
70 if (nla_len(opt) < sizeof(*ctl))
73 sch->limit = ctl->limit;
77 bypass = sch->limit >= psched_mtu(qdisc_dev(sch));
79 bypass = sch->limit >= 1;
82 sch->flags |= TCQ_F_CAN_BYPASS;
84 sch->flags &= ~TCQ_F_CAN_BYPASS;
88 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
90 struct tc_fifo_qopt opt = { .limit = sch->limit };
92 if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
100 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
103 .enqueue = pfifo_enqueue,
104 .dequeue = qdisc_dequeue_head,
105 .peek = qdisc_peek_head,
107 .reset = qdisc_reset_queue,
110 .owner = THIS_MODULE,
112 EXPORT_SYMBOL(pfifo_qdisc_ops);
114 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
117 .enqueue = bfifo_enqueue,
118 .dequeue = qdisc_dequeue_head,
119 .peek = qdisc_peek_head,
121 .reset = qdisc_reset_queue,
124 .owner = THIS_MODULE,
126 EXPORT_SYMBOL(bfifo_qdisc_ops);
128 struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
129 .id = "pfifo_head_drop",
131 .enqueue = pfifo_tail_enqueue,
132 .dequeue = qdisc_dequeue_head,
133 .peek = qdisc_peek_head,
135 .reset = qdisc_reset_queue,
138 .owner = THIS_MODULE,
141 /* Pass size change message down to embedded FIFO */
142 int fifo_set_limit(struct Qdisc *q, unsigned int limit)
147 /* Hack to avoid sending change message to non-FIFO */
148 if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
151 nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
153 nla->nla_type = RTM_NEWQDISC;
154 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
155 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
157 ret = q->ops->change(q, nla, NULL);
162 EXPORT_SYMBOL(fifo_set_limit);
164 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
166 struct netlink_ext_ack *extack)
171 q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1),
174 err = fifo_set_limit(q, limit);
181 return q ? : ERR_PTR(err);
183 EXPORT_SYMBOL(fifo_create_dflt);