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); 185