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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                          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                      struct netlink_ext_ack *extack)
 60 {
 61         bool bypass;
 62         bool is_bfifo = sch->ops == &bfifo_qdisc_ops;
 63 
 64         if (opt == NULL) {
 65                 u32 limit = qdisc_dev(sch)->tx_queue_len;
 66 
 67                 if (is_bfifo)
 68                         limit *= psched_mtu(qdisc_dev(sch));
 69 
 70                 sch->limit = limit;
 71         } else {
 72                 struct tc_fifo_qopt *ctl = nla_data(opt);
 73 
 74                 if (nla_len(opt) < sizeof(*ctl))
 75                         return -EINVAL;
 76 
 77                 sch->limit = ctl->limit;
 78         }
 79 
 80         if (is_bfifo)
 81                 bypass = sch->limit >= psched_mtu(qdisc_dev(sch));
 82         else
 83                 bypass = sch->limit >= 1;
 84 
 85         if (bypass)
 86                 sch->flags |= TCQ_F_CAN_BYPASS;
 87         else
 88                 sch->flags &= ~TCQ_F_CAN_BYPASS;
 89         return 0;
 90 }
 91 
 92 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
 93 {
 94         struct tc_fifo_qopt opt = { .limit = sch->limit };
 95 
 96         if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
 97                 goto nla_put_failure;
 98         return skb->len;
 99 
100 nla_put_failure:
101         return -1;
102 }
103 
104 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
105         .id             =       "pfifo",
106         .priv_size      =       0,
107         .enqueue        =       pfifo_enqueue,
108         .dequeue        =       qdisc_dequeue_head,
109         .peek           =       qdisc_peek_head,
110         .init           =       fifo_init,
111         .reset          =       qdisc_reset_queue,
112         .change         =       fifo_init,
113         .dump           =       fifo_dump,
114         .owner          =       THIS_MODULE,
115 };
116 EXPORT_SYMBOL(pfifo_qdisc_ops);
117 
118 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
119         .id             =       "bfifo",
120         .priv_size      =       0,
121         .enqueue        =       bfifo_enqueue,
122         .dequeue        =       qdisc_dequeue_head,
123         .peek           =       qdisc_peek_head,
124         .init           =       fifo_init,
125         .reset          =       qdisc_reset_queue,
126         .change         =       fifo_init,
127         .dump           =       fifo_dump,
128         .owner          =       THIS_MODULE,
129 };
130 EXPORT_SYMBOL(bfifo_qdisc_ops);
131 
132 struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
133         .id             =       "pfifo_head_drop",
134         .priv_size      =       0,
135         .enqueue        =       pfifo_tail_enqueue,
136         .dequeue        =       qdisc_dequeue_head,
137         .peek           =       qdisc_peek_head,
138         .init           =       fifo_init,
139         .reset          =       qdisc_reset_queue,
140         .change         =       fifo_init,
141         .dump           =       fifo_dump,
142         .owner          =       THIS_MODULE,
143 };
144 
145 /* Pass size change message down to embedded FIFO */
146 int fifo_set_limit(struct Qdisc *q, unsigned int limit)
147 {
148         struct nlattr *nla;
149         int ret = -ENOMEM;
150 
151         /* Hack to avoid sending change message to non-FIFO */
152         if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
153                 return 0;
154 
155         nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
156         if (nla) {
157                 nla->nla_type = RTM_NEWQDISC;
158                 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
159                 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
160 
161                 ret = q->ops->change(q, nla, NULL);
162                 kfree(nla);
163         }
164         return ret;
165 }
166 EXPORT_SYMBOL(fifo_set_limit);
167 
168 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
169                                unsigned int limit,
170                                struct netlink_ext_ack *extack)
171 {
172         struct Qdisc *q;
173         int err = -ENOMEM;
174 
175         q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1),
176                               extack);
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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