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Linux/net/sched/sch_fifo.c

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  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 
 16 /* 1 band FIFO pseudo-"scheduler" */
 17 
 18 static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 19                          struct sk_buff **to_free)
 20 {
 21         if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit))
 22                 return qdisc_enqueue_tail(skb, sch);
 23 
 24         return qdisc_drop(skb, sch, to_free);
 25 }
 26 
 27 static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 28                          struct sk_buff **to_free)
 29 {
 30         if (likely(sch->q.qlen < sch->limit))
 31                 return qdisc_enqueue_tail(skb, sch);
 32 
 33         return qdisc_drop(skb, sch, to_free);
 34 }
 35 
 36 static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 37                               struct sk_buff **to_free)
 38 {
 39         unsigned int prev_backlog;
 40 
 41         if (likely(sch->q.qlen < sch->limit))
 42                 return qdisc_enqueue_tail(skb, sch);
 43 
 44         prev_backlog = sch->qstats.backlog;
 45         /* queue full, remove one skb to fulfill the limit */
 46         __qdisc_queue_drop_head(sch, &sch->q, to_free);
 47         qdisc_qstats_drop(sch);
 48         qdisc_enqueue_tail(skb, sch);
 49 
 50         qdisc_tree_reduce_backlog(sch, 0, prev_backlog - sch->qstats.backlog);
 51         return NET_XMIT_CN;
 52 }
 53 
 54 static int fifo_init(struct Qdisc *sch, struct nlattr *opt,
 55                      struct netlink_ext_ack *extack)
 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         .init           =       fifo_init,
107         .reset          =       qdisc_reset_queue,
108         .change         =       fifo_init,
109         .dump           =       fifo_dump,
110         .owner          =       THIS_MODULE,
111 };
112 EXPORT_SYMBOL(pfifo_qdisc_ops);
113 
114 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
115         .id             =       "bfifo",
116         .priv_size      =       0,
117         .enqueue        =       bfifo_enqueue,
118         .dequeue        =       qdisc_dequeue_head,
119         .peek           =       qdisc_peek_head,
120         .init           =       fifo_init,
121         .reset          =       qdisc_reset_queue,
122         .change         =       fifo_init,
123         .dump           =       fifo_dump,
124         .owner          =       THIS_MODULE,
125 };
126 EXPORT_SYMBOL(bfifo_qdisc_ops);
127 
128 struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
129         .id             =       "pfifo_head_drop",
130         .priv_size      =       0,
131         .enqueue        =       pfifo_tail_enqueue,
132         .dequeue        =       qdisc_dequeue_head,
133         .peek           =       qdisc_peek_head,
134         .init           =       fifo_init,
135         .reset          =       qdisc_reset_queue,
136         .change         =       fifo_init,
137         .dump           =       fifo_dump,
138         .owner          =       THIS_MODULE,
139 };
140 
141 /* Pass size change message down to embedded FIFO */
142 int fifo_set_limit(struct Qdisc *q, unsigned int limit)
143 {
144         struct nlattr *nla;
145         int ret = -ENOMEM;
146 
147         /* Hack to avoid sending change message to non-FIFO */
148         if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
149                 return 0;
150 
151         nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
152         if (nla) {
153                 nla->nla_type = RTM_NEWQDISC;
154                 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
155                 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
156 
157                 ret = q->ops->change(q, nla, NULL);
158                 kfree(nla);
159         }
160         return ret;
161 }
162 EXPORT_SYMBOL(fifo_set_limit);
163 
164 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
165                                unsigned int limit,
166                                struct netlink_ext_ack *extack)
167 {
168         struct Qdisc *q;
169         int err = -ENOMEM;
170 
171         q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1),
172                               extack);
173         if (q) {
174                 err = fifo_set_limit(q, limit);
175                 if (err < 0) {
176                         qdisc_put(q);
177                         q = NULL;
178                 }
179         }
180 
181         return q ? : ERR_PTR(err);
182 }
183 EXPORT_SYMBOL(fifo_create_dflt);
184 

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