Documentation: move nfsroot.txt to filesystems/
[linux-2.6] / net / ipv4 / ipvs / ip_vs_rr.c
1 /*
2  * IPVS:        Round-Robin Scheduling module
3  *
4  * Version:     $Id: ip_vs_rr.c,v 1.9 2002/09/15 08:14:08 wensong Exp $
5  *
6  * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
7  *              Peter Kese <peter.kese@ijs.si>
8  *
9  *              This program is free software; you can redistribute it and/or
10  *              modify it under the terms of the GNU General Public License
11  *              as published by the Free Software Foundation; either version
12  *              2 of the License, or (at your option) any later version.
13  *
14  * Fixes/Changes:
15  *     Wensong Zhang            :     changed the ip_vs_rr_schedule to return dest
16  *     Julian Anastasov         :     fixed the NULL pointer access bug in debugging
17  *     Wensong Zhang            :     changed some comestics things for debugging
18  *     Wensong Zhang            :     changed for the d-linked destination list
19  *     Wensong Zhang            :     added the ip_vs_rr_update_svc
20  *     Wensong Zhang            :     added any dest with weight=0 is quiesced
21  *
22  */
23
24 #include <linux/module.h>
25 #include <linux/kernel.h>
26
27 #include <net/ip_vs.h>
28
29
30 static int ip_vs_rr_init_svc(struct ip_vs_service *svc)
31 {
32         svc->sched_data = &svc->destinations;
33         return 0;
34 }
35
36
37 static int ip_vs_rr_done_svc(struct ip_vs_service *svc)
38 {
39         return 0;
40 }
41
42
43 static int ip_vs_rr_update_svc(struct ip_vs_service *svc)
44 {
45         svc->sched_data = &svc->destinations;
46         return 0;
47 }
48
49
50 /*
51  * Round-Robin Scheduling
52  */
53 static struct ip_vs_dest *
54 ip_vs_rr_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
55 {
56         struct list_head *p, *q;
57         struct ip_vs_dest *dest;
58
59         IP_VS_DBG(6, "ip_vs_rr_schedule(): Scheduling...\n");
60
61         write_lock(&svc->sched_lock);
62         p = (struct list_head *)svc->sched_data;
63         p = p->next;
64         q = p;
65         do {
66                 /* skip list head */
67                 if (q == &svc->destinations) {
68                         q = q->next;
69                         continue;
70                 }
71
72                 dest = list_entry(q, struct ip_vs_dest, n_list);
73                 if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
74                     atomic_read(&dest->weight) > 0)
75                         /* HIT */
76                         goto out;
77                 q = q->next;
78         } while (q != p);
79         write_unlock(&svc->sched_lock);
80         return NULL;
81
82   out:
83         svc->sched_data = q;
84         write_unlock(&svc->sched_lock);
85         IP_VS_DBG(6, "RR: server %u.%u.%u.%u:%u "
86                   "activeconns %d refcnt %d weight %d\n",
87                   NIPQUAD(dest->addr), ntohs(dest->port),
88                   atomic_read(&dest->activeconns),
89                   atomic_read(&dest->refcnt), atomic_read(&dest->weight));
90
91         return dest;
92 }
93
94
95 static struct ip_vs_scheduler ip_vs_rr_scheduler = {
96         .name =                 "rr",                   /* name */
97         .refcnt =               ATOMIC_INIT(0),
98         .module =               THIS_MODULE,
99         .init_service =         ip_vs_rr_init_svc,
100         .done_service =         ip_vs_rr_done_svc,
101         .update_service =       ip_vs_rr_update_svc,
102         .schedule =             ip_vs_rr_schedule,
103 };
104
105 static int __init ip_vs_rr_init(void)
106 {
107         INIT_LIST_HEAD(&ip_vs_rr_scheduler.n_list);
108         return register_ip_vs_scheduler(&ip_vs_rr_scheduler);
109 }
110
111 static void __exit ip_vs_rr_cleanup(void)
112 {
113         unregister_ip_vs_scheduler(&ip_vs_rr_scheduler);
114 }
115
116 module_init(ip_vs_rr_init);
117 module_exit(ip_vs_rr_cleanup);
118 MODULE_LICENSE("GPL");