net/sched/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
  19 static 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) <= sch->limit))
  23                 return qdisc_enqueue_tail(skb, sch);
  24
  25         return qdisc_drop(skb, sch, to_free);
  26 }
  27
  28 static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
  29                          struct sk_buff **to_free)
  30 {
  31         if (likely(sch->q.qlen < sch->limit))
  32                 return qdisc_enqueue_tail(skb, sch);
  33
  34         return qdisc_drop(skb, sch, to_free);
  35 }
  36
  37 static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch,
  38                               struct sk_buff **to_free)
  39 {
  40         unsigned int prev_backlog;
  41
  42         if (likely(sch->q.qlen < 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, to_free);
  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 void fifo_offload_init(struct Qdisc *sch)
  56 {
  57         struct net_device *dev = qdisc_dev(sch);
  58         struct tc_fifo_qopt_offload qopt;
  59
  60         if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
  61                 return;
  62
  63         qopt.command = TC_FIFO_REPLACE;
  64         qopt.handle = sch->handle;
  65         qopt.parent = sch->parent;
  66         dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_FIFO, &qopt);
  67 }
  68
  69 static void fifo_offload_destroy(struct Qdisc *sch)
  70 {
  71         struct net_device *dev = qdisc_dev(sch);
  72         struct tc_fifo_qopt_offload qopt;
  73
  74         if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
  75                 return;
  76
  77         qopt.command = TC_FIFO_DESTROY;
  78         qopt.handle = sch->handle;
  79         qopt.parent = sch->parent;
  80         dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_FIFO, &qopt);
  81 }
  82
  83 static int fifo_offload_dump(struct Qdisc *sch)
  84 {
  85         struct tc_fifo_qopt_offload qopt;
  86
  87         qopt.command = TC_FIFO_STATS;
  88         qopt.handle = sch->handle;
  89         qopt.parent = sch->parent;
  90         qopt.stats.bstats = &sch->bstats;
  91         qopt.stats.qstats = &sch->qstats;
  92
  93         return qdisc_offload_dump_helper(sch, TC_SETUP_QDISC_FIFO, &qopt);
  94 }
  95
  96 static int __fifo_init(struct Qdisc *sch, struct nlattr *opt,
  97                        struct netlink_ext_ack *extack)
  98 {
  99         bool bypass;
 100         bool is_bfifo = sch->ops == &bfifo_qdisc_ops;
 101
 102         if (opt == NULL) {
 103                 u32 limit = qdisc_dev(sch)->tx_queue_len;
 104
 105                 if (is_bfifo)
 106                         limit *= psched_mtu(qdisc_dev(sch));
 107
 108                 sch->limit = limit;
 109         } else {
 110                 struct tc_fifo_qopt *ctl = nla_data(opt);
 111
 112                 if (nla_len(opt) < sizeof(*ctl))
 113                         return -EINVAL;
 114
 115                 sch->limit = ctl->limit;
 116         }
 117
 118         if (is_bfifo)
 119                 bypass = sch->limit >= psched_mtu(qdisc_dev(sch));
 120         else
 121                 bypass = sch->limit >= 1;
 122
 123         if (bypass)
 124                 sch->flags |= TCQ_F_CAN_BYPASS;
 125         else
 126                 sch->flags &= ~TCQ_F_CAN_BYPASS;
 127
 128         return 0;
 129 }
 130
 131 static int fifo_init(struct Qdisc *sch, struct nlattr *opt,
 132                      struct netlink_ext_ack *extack)
 133 {
 134         int err;
 135
 136         err = __fifo_init(sch, opt, extack);
 137         if (err)
 138                 return err;
 139
 140         fifo_offload_init(sch);
 141         return 0;
 142 }
 143
 144 static int fifo_hd_init(struct Qdisc *sch, struct nlattr *opt,
 145                         struct netlink_ext_ack *extack)
 146 {
 147         return __fifo_init(sch, opt, extack);
 148 }
 149
 150 static void fifo_destroy(struct Qdisc *sch)
 151 {
 152         fifo_offload_destroy(sch);
 153 }
 154
 155 static int __fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
 156 {
 157         struct tc_fifo_qopt opt = { .limit = sch->limit };
 158
 159         if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
 160                 goto nla_put_failure;
 161         return skb->len;
 162
 163 nla_put_failure:
 164         return -1;
 165 }
 166
 167 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
 168 {
 169         int err;
 170
 171         err = fifo_offload_dump(sch);
 172         if (err)
 173                 return err;
 174
 175         return __fifo_dump(sch, skb);
 176 }
 177
 178 static int fifo_hd_dump(struct Qdisc *sch, struct sk_buff *skb)
 179 {
 180         return __fifo_dump(sch, skb);
 181 }
 182
 183 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
 184         .id             =       "pfifo",
 185         .priv_size      =       0,
 186         .enqueue        =       pfifo_enqueue,
 187         .dequeue        =       qdisc_dequeue_head,
 188         .peek           =       qdisc_peek_head,
 189         .init           =       fifo_init,
 190         .destroy        =       fifo_destroy,
 191         .reset          =       qdisc_reset_queue,
 192         .change         =       fifo_init,
 193         .dump           =       fifo_dump,
 194         .owner          =       THIS_MODULE,
 195 };
 196 EXPORT_SYMBOL(pfifo_qdisc_ops);
 197
 198 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
 199         .id             =       "bfifo",
 200         .priv_size      =       0,
 201         .enqueue        =       bfifo_enqueue,
 202         .dequeue        =       qdisc_dequeue_head,
 203         .peek           =       qdisc_peek_head,
 204         .init           =       fifo_init,
 205         .destroy        =       fifo_destroy,
 206         .reset          =       qdisc_reset_queue,
 207         .change         =       fifo_init,
 208         .dump           =       fifo_dump,
 209         .owner          =       THIS_MODULE,
 210 };
 211 EXPORT_SYMBOL(bfifo_qdisc_ops);
 212
 213 struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
 214         .id             =       "pfifo_head_drop",
 215         .priv_size      =       0,
 216         .enqueue        =       pfifo_tail_enqueue,
 217         .dequeue        =       qdisc_dequeue_head,
 218         .peek           =       qdisc_peek_head,
 219         .init           =       fifo_hd_init,
 220         .reset          =       qdisc_reset_queue,
 221         .change         =       fifo_hd_init,
 222         .dump           =       fifo_hd_dump,
 223         .owner          =       THIS_MODULE,
 224 };
 225
 226 /* Pass size change message down to embedded FIFO */
 227 int fifo_set_limit(struct Qdisc *q, unsigned int limit)
 228 {
 229         struct nlattr *nla;
 230         int ret = -ENOMEM;
 231
 232         /* Hack to avoid sending change message to non-FIFO */
 233         if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
 234                 return 0;
 235
 236         nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
 237         if (nla) {
 238                 nla->nla_type = RTM_NEWQDISC;
 239                 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
 240                 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
 241
 242                 ret = q->ops->change(q, nla, NULL);
 243                 kfree(nla);
 244         }
 245         return ret;
 246 }
 247 EXPORT_SYMBOL(fifo_set_limit);
 248
 249 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
 250                                unsigned int limit,
 251                                struct netlink_ext_ack *extack)
 252 {
 253         struct Qdisc *q;
 254         int err = -ENOMEM;
 255
 256         q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1),
 257                               extack);
 258         if (q) {
 259                 err = fifo_set_limit(q, limit);
 260                 if (err < 0) {
 261                         qdisc_put(q);
 262                         q = NULL;
 263                 }
 264         }
 265
 266         return q ? : ERR_PTR(err);
 267 }
 268 EXPORT_SYMBOL(fifo_create_dflt);