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)58 ip_vs_rr_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
59 {
60 struct list_head *p;
61 struct ip_vs_dest *dest, *last;
62 int pass = 0;
63
64 IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
65
66 spin_lock_bh(&svc->sched_lock);
67 p = (struct list_head *) svc->sched_data;
68 last = dest = list_entry(p, struct ip_vs_dest, n_list);
69
70 do {
71 list_for_each_entry_continue_rcu(dest,
72 &svc->destinations,
73 n_list) {
74 if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
75 atomic_read(&dest->weight) > 0)
76 /* HIT */
77 goto out;
78 if (dest == last)
79 goto stop;
80 }
81 pass++;
82 /* Previous dest could be unlinked, do not loop forever.
83 * If we stay at head there is no need for 2nd pass.
84 */
85 } while (pass < 2 && p != &svc->destinations);
86
87 stop:
88 spin_unlock_bh(&svc->sched_lock);
89 ip_vs_scheduler_err(svc, "no destination available");
90 return NULL;
91
92 out:
93 svc->sched_data = &dest->n_list;
94 spin_unlock_bh(&svc->sched_lock);
95 IP_VS_DBG_BUF(6, "RR: server %s:%u "
96 "activeconns %d refcnt %d weight %d\n",
97 IP_VS_DBG_ADDR(svc->af, &dest->addr), ntohs(dest->port),
98 atomic_read(&dest->activeconns),
99 atomic_read(&dest->refcnt), atomic_read(&dest->weight));
100
101 return dest;
102 }
103
104
105 static struct ip_vs_scheduler ip_vs_rr_scheduler = {
106 .name = "rr", /* name */
107 .refcnt = ATOMIC_INIT(0),
108 .module = THIS_MODULE,
109 .n_list = LIST_HEAD_INIT(ip_vs_rr_scheduler.n_list),
110 .init_service = ip_vs_rr_init_svc,
111 .add_dest = NULL,
112 .del_dest = ip_vs_rr_del_dest,
113 .schedule = ip_vs_rr_schedule,
114 };
115
ip_vs_rr_init(void)116 static int __init ip_vs_rr_init(void)
117 {
118 return register_ip_vs_scheduler(&ip_vs_rr_scheduler);
119 }
120
ip_vs_rr_cleanup(void)121 static void __exit ip_vs_rr_cleanup(void)
122 {
123 unregister_ip_vs_scheduler(&ip_vs_rr_scheduler);
124 synchronize_rcu();
125 }
126
127 module_init(ip_vs_rr_init);
128 module_exit(ip_vs_rr_cleanup);
129 MODULE_LICENSE("GPL");
130