1 /*
2 * IPVS: Round-Robin Scheduling module
3 *
4 * Authors: Wensong Zhang <wensong@linuxvirtualserver.org>
5 * Peter Kese <peter.kese@ijs.si>
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; either version
10 * 2 of the License, or (at your option) any later version.
11 *
12 * Fixes/Changes:
13 * Wensong Zhang : changed the ip_vs_rr_schedule to return dest
14 * Julian Anastasov : fixed the NULL pointer access bug in debugging
15 * Wensong Zhang : changed some comestics things for debugging
16 * Wensong Zhang : changed for the d-linked destination list
17 * Wensong Zhang : added the ip_vs_rr_update_svc
18 * Wensong Zhang : added any dest with weight=0 is quiesced
19 *
20 */
21
22 #define KMSG_COMPONENT "IPVS"
23 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
24
25 #include <linux/module.h>
26 #include <linux/kernel.h>
27
28 #include <net/ip_vs.h>
29
30
ip_vs_rr_init_svc(struct ip_vs_service * svc)31 static int ip_vs_rr_init_svc(struct ip_vs_service *svc)
32 {
33 svc->sched_data = &svc->destinations;
34 return 0;
35 }
36
37
ip_vs_rr_del_dest(struct ip_vs_service * svc,struct ip_vs_dest * dest)38 static int ip_vs_rr_del_dest(struct ip_vs_service *svc, struct ip_vs_dest *dest)
39 {
40 struct list_head *p;
41
42 spin_lock_bh(&svc->sched_lock);
43 p = (struct list_head *) svc->sched_data;
44 /* dest is already unlinked, so p->prev is not valid but
45 * p->next is valid, use it to reach previous entry.
46 */
47 if (p == &dest->n_list)
48 svc->sched_data = p->next->prev;
49 spin_unlock_bh(&svc->sched_lock);
50 return 0;
51 }
52
53
54 /*
55 * Round-Robin Scheduling
56 */
57 static struct ip_vs_dest *
ip_vs_rr_schedule(struct ip_vs_service * svc,const struct sk_buff * skb,struct ip_vs_iphdr * iph)58 ip_vs_rr_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
59 struct ip_vs_iphdr *iph)
60 {
61 struct list_head *p;
62 struct ip_vs_dest *dest, *last;
63 int pass = 0;
64
65 IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
66
67 spin_lock_bh(&svc->sched_lock);
68 p = (struct list_head *) svc->sched_data;
69 last = dest = list_entry(p, struct ip_vs_dest, n_list);
70
71 do {
72 list_for_each_entry_continue_rcu(dest,
73 &svc->destinations,
74 n_list) {
75 if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
76 atomic_read(&dest->weight) > 0)
77 /* HIT */
78 goto out;
79 if (dest == last)
80 goto stop;
81 }
82 pass++;
83 /* Previous dest could be unlinked, do not loop forever.
84 * If we stay at head there is no need for 2nd pass.
85 */
86 } while (pass < 2 && p != &svc->destinations);
87
88 stop:
89 spin_unlock_bh(&svc->sched_lock);
90 ip_vs_scheduler_err(svc, "no destination available");
91 return NULL;
92
93 out:
94 svc->sched_data = &dest->n_list;
95 spin_unlock_bh(&svc->sched_lock);
96 IP_VS_DBG_BUF(6, "RR: server %s:%u "
97 "activeconns %d refcnt %d weight %d\n",
98 IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port),
99 atomic_read(&dest->activeconns),
100 atomic_read(&dest->refcnt), atomic_read(&dest->weight));
101
102 return dest;
103 }
104
105
106 static struct ip_vs_scheduler ip_vs_rr_scheduler = {
107 .name = "rr", /* name */
108 .refcnt = ATOMIC_INIT(0),
109 .module = THIS_MODULE,
110 .n_list = LIST_HEAD_INIT(ip_vs_rr_scheduler.n_list),
111 .init_service = ip_vs_rr_init_svc,
112 .add_dest = NULL,
113 .del_dest = ip_vs_rr_del_dest,
114 .schedule = ip_vs_rr_schedule,
115 };
116
ip_vs_rr_init(void)117 static int __init ip_vs_rr_init(void)
118 {
119 return register_ip_vs_scheduler(&ip_vs_rr_scheduler);
120 }
121
ip_vs_rr_cleanup(void)122 static void __exit ip_vs_rr_cleanup(void)
123 {
124 unregister_ip_vs_scheduler(&ip_vs_rr_scheduler);
125 synchronize_rcu();
126 }
127
128 module_init(ip_vs_rr_init);
129 module_exit(ip_vs_rr_cleanup);
130 MODULE_LICENSE("GPL");
131