xref: /openbmc/linux/net/sched/sch_fifo.c (revision 22246614)
1 /*
2  * net/sched/sch_fifo.c	The simplest FIFO queue.
3  *
4  *		This program is free software; you can redistribute it and/or
5  *		modify it under the terms of the GNU General Public License
6  *		as published by the Free Software Foundation; either version
7  *		2 of the License, or (at your option) any later version.
8  *
9  * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
10  */
11 
12 #include <linux/module.h>
13 #include <linux/types.h>
14 #include <linux/kernel.h>
15 #include <linux/errno.h>
16 #include <linux/skbuff.h>
17 #include <net/pkt_sched.h>
18 
19 /* 1 band FIFO pseudo-"scheduler" */
20 
21 struct fifo_sched_data
22 {
23 	u32 limit;
24 };
25 
26 static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc* sch)
27 {
28 	struct fifo_sched_data *q = qdisc_priv(sch);
29 
30 	if (likely(sch->qstats.backlog + skb->len <= q->limit))
31 		return qdisc_enqueue_tail(skb, sch);
32 
33 	return qdisc_reshape_fail(skb, sch);
34 }
35 
36 static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc* sch)
37 {
38 	struct fifo_sched_data *q = qdisc_priv(sch);
39 
40 	if (likely(skb_queue_len(&sch->q) < q->limit))
41 		return qdisc_enqueue_tail(skb, sch);
42 
43 	return qdisc_reshape_fail(skb, sch);
44 }
45 
46 static int fifo_init(struct Qdisc *sch, struct nlattr *opt)
47 {
48 	struct fifo_sched_data *q = qdisc_priv(sch);
49 
50 	if (opt == NULL) {
51 		u32 limit = sch->dev->tx_queue_len ? : 1;
52 
53 		if (sch->ops == &bfifo_qdisc_ops)
54 			limit *= sch->dev->mtu;
55 
56 		q->limit = limit;
57 	} else {
58 		struct tc_fifo_qopt *ctl = nla_data(opt);
59 
60 		if (nla_len(opt) < sizeof(*ctl))
61 			return -EINVAL;
62 
63 		q->limit = ctl->limit;
64 	}
65 
66 	return 0;
67 }
68 
69 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
70 {
71 	struct fifo_sched_data *q = qdisc_priv(sch);
72 	struct tc_fifo_qopt opt = { .limit = q->limit };
73 
74 	NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
75 	return skb->len;
76 
77 nla_put_failure:
78 	return -1;
79 }
80 
81 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
82 	.id		=	"pfifo",
83 	.priv_size	=	sizeof(struct fifo_sched_data),
84 	.enqueue	=	pfifo_enqueue,
85 	.dequeue	=	qdisc_dequeue_head,
86 	.requeue	=	qdisc_requeue,
87 	.drop		=	qdisc_queue_drop,
88 	.init		=	fifo_init,
89 	.reset		=	qdisc_reset_queue,
90 	.change		=	fifo_init,
91 	.dump		=	fifo_dump,
92 	.owner		=	THIS_MODULE,
93 };
94 EXPORT_SYMBOL(pfifo_qdisc_ops);
95 
96 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
97 	.id		=	"bfifo",
98 	.priv_size	=	sizeof(struct fifo_sched_data),
99 	.enqueue	=	bfifo_enqueue,
100 	.dequeue	=	qdisc_dequeue_head,
101 	.requeue	=	qdisc_requeue,
102 	.drop		=	qdisc_queue_drop,
103 	.init		=	fifo_init,
104 	.reset		=	qdisc_reset_queue,
105 	.change		=	fifo_init,
106 	.dump		=	fifo_dump,
107 	.owner		=	THIS_MODULE,
108 };
109 EXPORT_SYMBOL(bfifo_qdisc_ops);
110