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Linux/net/sched/sch_fifo.c

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  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/slab.h>
 14 #include <linux/types.h>
 15 #include <linux/kernel.h>
 16 #include <linux/errno.h>
 17 #include <linux/skbuff.h>
 18 #include <net/pkt_sched.h>
 19 
 20 /* 1 band FIFO pseudo-"scheduler" */
 21 
 22 static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 23 {
 24         if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit))
 25                 return qdisc_enqueue_tail(skb, sch);
 26 
 27         return qdisc_reshape_fail(skb, sch);
 28 }
 29 
 30 static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 31 {
 32         if (likely(skb_queue_len(&sch->q) < sch->limit))
 33                 return qdisc_enqueue_tail(skb, sch);
 34 
 35         return qdisc_reshape_fail(skb, sch);
 36 }
 37 
 38 static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 39 {
 40         unsigned int prev_backlog;
 41 
 42         if (likely(skb_queue_len(&sch->q) < sch->limit))
 43                 return qdisc_enqueue_tail(skb, sch);
 44 
 45         prev_backlog = sch->qstats.backlog;
 46         /* queue full, remove one skb to fulfill the limit */
 47         __qdisc_queue_drop_head(sch, &sch->q);
 48         qdisc_qstats_drop(sch);
 49         qdisc_enqueue_tail(skb, sch);
 50 
 51         qdisc_tree_reduce_backlog(sch, 0, prev_backlog - sch->qstats.backlog);
 52         return NET_XMIT_CN;
 53 }
 54 
 55 static int fifo_init(struct Qdisc *sch, struct nlattr *opt)
 56 {
 57         bool bypass;
 58         bool is_bfifo = sch->ops == &bfifo_qdisc_ops;
 59 
 60         if (opt == NULL) {
 61                 u32 limit = qdisc_dev(sch)->tx_queue_len;
 62 
 63                 if (is_bfifo)
 64                         limit *= psched_mtu(qdisc_dev(sch));
 65 
 66                 sch->limit = limit;
 67         } else {
 68                 struct tc_fifo_qopt *ctl = nla_data(opt);
 69 
 70                 if (nla_len(opt) < sizeof(*ctl))
 71                         return -EINVAL;
 72 
 73                 sch->limit = ctl->limit;
 74         }
 75 
 76         if (is_bfifo)
 77                 bypass = sch->limit >= psched_mtu(qdisc_dev(sch));
 78         else
 79                 bypass = sch->limit >= 1;
 80 
 81         if (bypass)
 82                 sch->flags |= TCQ_F_CAN_BYPASS;
 83         else
 84                 sch->flags &= ~TCQ_F_CAN_BYPASS;
 85         return 0;
 86 }
 87 
 88 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
 89 {
 90         struct tc_fifo_qopt opt = { .limit = sch->limit };
 91 
 92         if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
 93                 goto nla_put_failure;
 94         return skb->len;
 95 
 96 nla_put_failure:
 97         return -1;
 98 }
 99 
100 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
101         .id             =       "pfifo",
102         .priv_size      =       0,
103         .enqueue        =       pfifo_enqueue,
104         .dequeue        =       qdisc_dequeue_head,
105         .peek           =       qdisc_peek_head,
106         .drop           =       qdisc_queue_drop,
107         .init           =       fifo_init,
108         .reset          =       qdisc_reset_queue,
109         .change         =       fifo_init,
110         .dump           =       fifo_dump,
111         .owner          =       THIS_MODULE,
112 };
113 EXPORT_SYMBOL(pfifo_qdisc_ops);
114 
115 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
116         .id             =       "bfifo",
117         .priv_size      =       0,
118         .enqueue        =       bfifo_enqueue,
119         .dequeue        =       qdisc_dequeue_head,
120         .peek           =       qdisc_peek_head,
121         .drop           =       qdisc_queue_drop,
122         .init           =       fifo_init,
123         .reset          =       qdisc_reset_queue,
124         .change         =       fifo_init,
125         .dump           =       fifo_dump,
126         .owner          =       THIS_MODULE,
127 };
128 EXPORT_SYMBOL(bfifo_qdisc_ops);
129 
130 struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
131         .id             =       "pfifo_head_drop",
132         .priv_size      =       0,
133         .enqueue        =       pfifo_tail_enqueue,
134         .dequeue        =       qdisc_dequeue_head,
135         .peek           =       qdisc_peek_head,
136         .drop           =       qdisc_queue_drop_head,
137         .init           =       fifo_init,
138         .reset          =       qdisc_reset_queue,
139         .change         =       fifo_init,
140         .dump           =       fifo_dump,
141         .owner          =       THIS_MODULE,
142 };
143 
144 /* Pass size change message down to embedded FIFO */
145 int fifo_set_limit(struct Qdisc *q, unsigned int limit)
146 {
147         struct nlattr *nla;
148         int ret = -ENOMEM;
149 
150         /* Hack to avoid sending change message to non-FIFO */
151         if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
152                 return 0;
153 
154         if (!q->ops->change)
155                 return 0;
156 
157         nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
158         if (nla) {
159                 nla->nla_type = RTM_NEWQDISC;
160                 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
161                 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
162 
163                 ret = q->ops->change(q, nla);
164                 kfree(nla);
165         }
166         return ret;
167 }
168 EXPORT_SYMBOL(fifo_set_limit);
169 
170 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
171                                unsigned int limit)
172 {
173         struct Qdisc *q;
174         int err = -ENOMEM;
175 
176         q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1));
177         if (q) {
178                 err = fifo_set_limit(q, limit);
179                 if (err < 0) {
180                         qdisc_destroy(q);
181                         q = NULL;
182                 }
183         }
184 
185         return q ? : ERR_PTR(err);
186 }
187 EXPORT_SYMBOL(fifo_create_dflt);
188 

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