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) <=
  23                    READ_ONCE(sch->limit)))
  24                 return qdisc_enqueue_tail(skb, sch);
  25
  26         return qdisc_drop(skb, sch, to_free);
  27 }
  28
  29 static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
  30                          struct sk_buff **to_free)
  31 {
  32         if (likely(sch->q.qlen < READ_ONCE(sch->limit)))
  33                 return qdisc_enqueue_tail(skb, sch);
  34
  35         return qdisc_drop(skb, sch, to_free);
  36 }
  37
  38 static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch,
  39                               struct sk_buff **to_free)
  40 {
  41         unsigned int prev_backlog;
  42
  43         if (likely(sch->q.qlen < READ_ONCE(sch->limit)))
  44                 return qdisc_enqueue_tail(skb, sch);
  45
  46         prev_backlog = sch->qstats.backlog;
  47         /* queue full, remove one skb to fulfill the limit */
  48         __qdisc_queue_drop_head(sch, &sch->q, to_free);
  49         qdisc_qstats_drop(sch);
  50         qdisc_enqueue_tail(skb, sch);
  51
  52         qdisc_tree_reduce_backlog(sch, 0, prev_backlog - sch->qstats.backlog);
  53         return NET_XMIT_CN;
  54 }
  55
  56 static void fifo_offload_init(struct Qdisc *sch)
  57 {
  58         struct net_device *dev = qdisc_dev(sch);
  59         struct tc_fifo_qopt_offload qopt;
  60
  61         if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
  62                 return;
  63
  64         qopt.command = TC_FIFO_REPLACE;
  65         qopt.handle = sch->handle;
  66         qopt.parent = sch->parent;
  67         dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_FIFO, &qopt);
  68 }
  69
  70 static void fifo_offload_destroy(struct Qdisc *sch)
  71 {
  72         struct net_device *dev = qdisc_dev(sch);
  73         struct tc_fifo_qopt_offload qopt;
  74
  75         if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
  76                 return;
  77
  78         qopt.command = TC_FIFO_DESTROY;
  79         qopt.handle = sch->handle;
  80         qopt.parent = sch->parent;
  81         dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_FIFO, &qopt);
  82 }
  83
  84 static int fifo_offload_dump(struct Qdisc *sch)
  85 {
  86         struct tc_fifo_qopt_offload qopt;
  87
  88         qopt.command = TC_FIFO_STATS;
  89         qopt.handle = sch->handle;
  90         qopt.parent = sch->parent;
  91         qopt.stats.bstats = &sch->bstats;
  92         qopt.stats.qstats = &sch->qstats;
  93
  94         return qdisc_offload_dump_helper(sch, TC_SETUP_QDISC_FIFO, &qopt);
  95 }
  96
  97 static int __fifo_init(struct Qdisc *sch, struct nlattr *opt,
  98                        struct netlink_ext_ack *extack)
  99 {
 100         bool bypass;
 101         bool is_bfifo = sch->ops == &bfifo_qdisc_ops;
 102
 103         if (opt == NULL) {
 104                 u32 limit = qdisc_dev(sch)->tx_queue_len;
 105
 106                 if (is_bfifo)
 107                         limit *= psched_mtu(qdisc_dev(sch));
 108
 109                 WRITE_ONCE(sch->limit, limit);
 110         } else {
 111                 struct tc_fifo_qopt *ctl = nla_data(opt);
 112
 113                 if (nla_len(opt) < sizeof(*ctl))
 114                         return -EINVAL;
 115
 116                 WRITE_ONCE(sch->limit, ctl->limit);
 117         }
 118
 119         if (is_bfifo)
 120                 bypass = sch->limit >= psched_mtu(qdisc_dev(sch));
 121         else
 122                 bypass = sch->limit >= 1;
 123
 124         if (bypass)
 125                 sch->flags |= TCQ_F_CAN_BYPASS;
 126         else
 127                 sch->flags &= ~TCQ_F_CAN_BYPASS;
 128
 129         return 0;
 130 }
 131
 132 static int fifo_init(struct Qdisc *sch, struct nlattr *opt,
 133                      struct netlink_ext_ack *extack)
 134 {
 135         int err;
 136
 137         err = __fifo_init(sch, opt, extack);
 138         if (err)
 139                 return err;
 140
 141         fifo_offload_init(sch);
 142         return 0;
 143 }
 144
 145 static int fifo_hd_init(struct Qdisc *sch, struct nlattr *opt,
 146                         struct netlink_ext_ack *extack)
 147 {
 148         return __fifo_init(sch, opt, extack);
 149 }
 150
 151 static void fifo_destroy(struct Qdisc *sch)
 152 {
 153         fifo_offload_destroy(sch);
 154 }
 155
 156 static int __fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
 157 {
 158         struct tc_fifo_qopt opt = { .limit = READ_ONCE(sch->limit) };
 159
 160         if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
 161                 goto nla_put_failure;
 162         return skb->len;
 163
 164 nla_put_failure:
 165         return -1;
 166 }
 167
 168 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
 169 {
 170         int err;
 171
 172         err = fifo_offload_dump(sch);
 173         if (err)
 174                 return err;
 175
 176         return __fifo_dump(sch, skb);
 177 }
 178
 179 static int fifo_hd_dump(struct Qdisc *sch, struct sk_buff *skb)
 180 {
 181         return __fifo_dump(sch, skb);
 182 }
 183
 184 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
 185         .id             =       "pfifo",
 186         .priv_size      =       0,
 187         .enqueue        =       pfifo_enqueue,
 188         .dequeue        =       qdisc_dequeue_head,
 189         .peek           =       qdisc_peek_head,
 190         .init           =       fifo_init,
 191         .destroy        =       fifo_destroy,
 192         .reset          =       qdisc_reset_queue,
 193         .change         =       fifo_init,
 194         .dump           =       fifo_dump,
 195         .owner          =       THIS_MODULE,
 196 };
 197 EXPORT_SYMBOL(pfifo_qdisc_ops);
 198
 199 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
 200         .id             =       "bfifo",
 201         .priv_size      =       0,
 202         .enqueue        =       bfifo_enqueue,
 203         .dequeue        =       qdisc_dequeue_head,
 204         .peek           =       qdisc_peek_head,
 205         .init           =       fifo_init,
 206         .destroy        =       fifo_destroy,
 207         .reset          =       qdisc_reset_queue,
 208         .change         =       fifo_init,
 209         .dump           =       fifo_dump,
 210         .owner          =       THIS_MODULE,
 211 };
 212 EXPORT_SYMBOL(bfifo_qdisc_ops);
 213
 214 struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
 215         .id             =       "pfifo_head_drop",
 216         .priv_size      =       0,
 217         .enqueue        =       pfifo_tail_enqueue,
 218         .dequeue        =       qdisc_dequeue_head,
 219         .peek           =       qdisc_peek_head,
 220         .init           =       fifo_hd_init,
 221         .reset          =       qdisc_reset_queue,
 222         .change         =       fifo_hd_init,
 223         .dump           =       fifo_hd_dump,
 224         .owner          =       THIS_MODULE,
 225 };
 226
 227 /* Pass size change message down to embedded FIFO */
 228 int fifo_set_limit(struct Qdisc *q, unsigned int limit)
 229 {
 230         struct nlattr *nla;
 231         int ret = -ENOMEM;
 232
 233         /* Hack to avoid sending change message to non-FIFO */
 234         if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
 235                 return 0;
 236
 237         if (!q->ops->change)
 238                 return 0;
 239
 240         nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
 241         if (nla) {
 242                 nla->nla_type = RTM_NEWQDISC;
 243                 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
 244                 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
 245
 246                 ret = q->ops->change(q, nla, NULL);
 247                 kfree(nla);
 248         }
 249         return ret;
 250 }
 251 EXPORT_SYMBOL(fifo_set_limit);
 252
 253 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
 254                                unsigned int limit,
 255                                struct netlink_ext_ack *extack)
 256 {
 257         struct Qdisc *q;
 258         int err = -ENOMEM;
 259
 260         q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1),
 261                               extack);
 262         if (q) {
 263                 err = fifo_set_limit(q, limit);
 264                 if (err < 0) {
 265                         qdisc_put(q);
 266                         q = NULL;
 267                 }
 268         }
 269
 270         return q ? : ERR_PTR(err);
 271 }
 272 EXPORT_SYMBOL(fifo_create_dflt);
 273 MODULE_DESCRIPTION("Single queue packet and byte based First In First Out(P/BFIFO) scheduler");