net/sched/sch_fifo.c

   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                          struct sk_buff **to_free)
  24 {
  25         if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit))
  26                 return qdisc_enqueue_tail(skb, sch);
  27
  28         return qdisc_drop(skb, sch, to_free);
  29 }
  30
  31 static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
  32                          struct sk_buff **to_free)
  33 {
  34         if (likely(sch->q.qlen < sch->limit))
  35                 return qdisc_enqueue_tail(skb, sch);
  36
  37         return qdisc_drop(skb, sch, to_free);
  38 }
  39
  40 static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch,
  41                               struct sk_buff **to_free)
  42 {
  43         unsigned int prev_backlog;
  44
  45         if (likely(sch->q.qlen < sch->limit))
  46                 return qdisc_enqueue_tail(skb, sch);
  47
  48         prev_backlog = sch->qstats.backlog;
  49         /* queue full, remove one skb to fulfill the limit */
  50         __qdisc_queue_drop_head(sch, &sch->q, to_free);
  51         qdisc_qstats_drop(sch);
  52         qdisc_enqueue_tail(skb, sch);
  53
  54         qdisc_tree_reduce_backlog(sch, 0, prev_backlog - sch->qstats.backlog);
  55         return NET_XMIT_CN;
  56 }
  57
  58 static int fifo_init(struct Qdisc *sch, struct nlattr *opt)
  59 {
  60         bool bypass;
  61         bool is_bfifo = sch->ops == &bfifo_qdisc_ops;
  62
  63         if (opt == NULL) {
  64                 u32 limit = qdisc_dev(sch)->tx_queue_len;
  65
  66                 if (is_bfifo)
  67                         limit *= psched_mtu(qdisc_dev(sch));
  68
  69                 sch->limit = limit;
  70         } else {
  71                 struct tc_fifo_qopt *ctl = nla_data(opt);
  72
  73                 if (nla_len(opt) < sizeof(*ctl))
  74                         return -EINVAL;
  75
  76                 sch->limit = ctl->limit;
  77         }
  78
  79         if (is_bfifo)
  80                 bypass = sch->limit >= psched_mtu(qdisc_dev(sch));
  81         else
  82                 bypass = sch->limit >= 1;
  83
  84         if (bypass)
  85                 sch->flags |= TCQ_F_CAN_BYPASS;
  86         else
  87                 sch->flags &= ~TCQ_F_CAN_BYPASS;
  88         return 0;
  89 }
  90
  91 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
  92 {
  93         struct tc_fifo_qopt opt = { .limit = sch->limit };
  94
  95         if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
  96                 goto nla_put_failure;
  97         return skb->len;
  98
  99 nla_put_failure:
 100         return -1;
 101 }
 102
 103 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
 104         .id             =       "pfifo",
 105         .priv_size      =       0,
 106         .enqueue        =       pfifo_enqueue,
 107         .dequeue        =       qdisc_dequeue_head,
 108         .peek           =       qdisc_peek_head,
 109         .init           =       fifo_init,
 110         .reset          =       qdisc_reset_queue,
 111         .change         =       fifo_init,
 112         .dump           =       fifo_dump,
 113         .owner          =       THIS_MODULE,
 114 };
 115 EXPORT_SYMBOL(pfifo_qdisc_ops);
 116
 117 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
 118         .id             =       "bfifo",
 119         .priv_size      =       0,
 120         .enqueue        =       bfifo_enqueue,
 121         .dequeue        =       qdisc_dequeue_head,
 122         .peek           =       qdisc_peek_head,
 123         .init           =       fifo_init,
 124         .reset          =       qdisc_reset_queue,
 125         .change         =       fifo_init,
 126         .dump           =       fifo_dump,
 127         .owner          =       THIS_MODULE,
 128 };
 129 EXPORT_SYMBOL(bfifo_qdisc_ops);
 130
 131 struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
 132         .id             =       "pfifo_head_drop",
 133         .priv_size      =       0,
 134         .enqueue        =       pfifo_tail_enqueue,
 135         .dequeue        =       qdisc_dequeue_head,
 136         .peek           =       qdisc_peek_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         nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
 155         if (nla) {
 156                 nla->nla_type = RTM_NEWQDISC;
 157                 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
 158                 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
 159
 160                 ret = q->ops->change(q, nla);
 161                 kfree(nla);
 162         }
 163         return ret;
 164 }
 165 EXPORT_SYMBOL(fifo_set_limit);
 166
 167 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
 168                                unsigned int limit)
 169 {
 170         struct Qdisc *q;
 171         int err = -ENOMEM;
 172
 173         q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1));
 174         if (q) {
 175                 err = fifo_set_limit(q, limit);
 176                 if (err < 0) {
 177                         qdisc_destroy(q);
 178                         q = NULL;
 179                 }
 180         }
 181
 182         return q ? : ERR_PTR(err);
 183 }
 184 EXPORT_SYMBOL(fifo_create_dflt);