net/ipv4/ipvs/ip_vs_rr.c

   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 #include <linux/module.h>
  23 #include <linux/kernel.h>
  24
  25 #include <net/ip_vs.h>
  26
  27
  28 static int ip_vs_rr_init_svc(struct ip_vs_service *svc)
  29 {
  30         svc->sched_data = &svc->destinations;
  31         return 0;
  32 }
  33
  34
  35 static int ip_vs_rr_update_svc(struct ip_vs_service *svc)
  36 {
  37         svc->sched_data = &svc->destinations;
  38         return 0;
  39 }
  40
  41
  42 /*
  43  * Round-Robin Scheduling
  44  */
  45 static struct ip_vs_dest *
  46 ip_vs_rr_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
  47 {
  48         struct list_head *p, *q;
  49         struct ip_vs_dest *dest;
  50
  51         IP_VS_DBG(6, "ip_vs_rr_schedule(): Scheduling...\n");
  52
  53         write_lock(&svc->sched_lock);
  54         p = (struct list_head *)svc->sched_data;
  55         p = p->next;
  56         q = p;
  57         do {
  58                 /* skip list head */
  59                 if (q == &svc->destinations) {
  60                         q = q->next;
  61                         continue;
  62                 }
  63
  64                 dest = list_entry(q, struct ip_vs_dest, n_list);
  65                 if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
  66                     atomic_read(&dest->weight) > 0)
  67                         /* HIT */
  68                         goto out;
  69                 q = q->next;
  70         } while (q != p);
  71         write_unlock(&svc->sched_lock);
  72         return NULL;
  73
  74   out:
  75         svc->sched_data = q;
  76         write_unlock(&svc->sched_lock);
  77         IP_VS_DBG(6, "RR: server %u.%u.%u.%u:%u "
  78                   "activeconns %d refcnt %d weight %d\n",
  79                   NIPQUAD(dest->addr), ntohs(dest->port),
  80                   atomic_read(&dest->activeconns),
  81                   atomic_read(&dest->refcnt), atomic_read(&dest->weight));
  82
  83         return dest;
  84 }
  85
  86
  87 static struct ip_vs_scheduler ip_vs_rr_scheduler = {
  88         .name =                 "rr",                   /* name */
  89         .refcnt =               ATOMIC_INIT(0),
  90         .module =               THIS_MODULE,
  91         .n_list =               LIST_HEAD_INIT(ip_vs_rr_scheduler.n_list),
  92         .init_service =         ip_vs_rr_init_svc,
  93         .update_service =       ip_vs_rr_update_svc,
  94         .schedule =             ip_vs_rr_schedule,
  95 };
  96
  97 static int __init ip_vs_rr_init(void)
  98 {
  99         return register_ip_vs_scheduler(&ip_vs_rr_scheduler);
 100 }
 101
 102 static void __exit ip_vs_rr_cleanup(void)
 103 {
 104         unregister_ip_vs_scheduler(&ip_vs_rr_scheduler);
 105 }
 106
 107 module_init(ip_vs_rr_init);
 108 module_exit(ip_vs_rr_cleanup);
 109 MODULE_LICENSE("GPL");