net/netfilter/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 #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
  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
  38 static int ip_vs_rr_update_svc(struct ip_vs_service *svc)
  39 {
  40         svc->sched_data = &svc->destinations;
  41         return 0;
  42 }
  43
  44
  45 /*
  46  * Round-Robin Scheduling
  47  */
  48 static struct ip_vs_dest *
  49 ip_vs_rr_schedule(struct ip_vs_service *svc, const struct sk_buff *skb)
  50 {
  51         struct list_head *p, *q;
  52         struct ip_vs_dest *dest;
  53
  54         IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
  55
  56         write_lock(&svc->sched_lock);
  57         p = (struct list_head *)svc->sched_data;
  58         p = p->next;
  59         q = p;
  60         do {
  61                 /* skip list head */
  62                 if (q == &svc->destinations) {
  63                         q = q->next;
  64                         continue;
  65                 }
  66
  67                 dest = list_entry(q, struct ip_vs_dest, n_list);
  68                 if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
  69                     atomic_read(&dest->weight) > 0)
  70                         /* HIT */
  71                         goto out;
  72                 q = q->next;
  73         } while (q != p);
  74         write_unlock(&svc->sched_lock);
  75         ip_vs_scheduler_err(svc, "no destination available");
  76         return NULL;
  77
  78   out:
  79         svc->sched_data = q;
  80         write_unlock(&svc->sched_lock);
  81         IP_VS_DBG_BUF(6, "RR: server %s:%u "
  82                       "activeconns %d refcnt %d weight %d\n",
  83                       IP_VS_DBG_ADDR(svc->af, &dest->addr), ntohs(dest->port),
  84                       atomic_read(&dest->activeconns),
  85                       atomic_read(&dest->refcnt), atomic_read(&dest->weight));
  86
  87         return dest;
  88 }
  89
  90
  91 static struct ip_vs_scheduler ip_vs_rr_scheduler = {
  92         .name =                 "rr",                   /* name */
  93         .refcnt =               ATOMIC_INIT(0),
  94         .module =               THIS_MODULE,
  95         .n_list =               LIST_HEAD_INIT(ip_vs_rr_scheduler.n_list),
  96         .init_service =         ip_vs_rr_init_svc,
  97         .update_service =       ip_vs_rr_update_svc,
  98         .schedule =             ip_vs_rr_schedule,
  99 };
 100
 101 static int __init ip_vs_rr_init(void)
 102 {
 103         return register_ip_vs_scheduler(&ip_vs_rr_scheduler);
 104 }
 105
 106 static void __exit ip_vs_rr_cleanup(void)
 107 {
 108         unregister_ip_vs_scheduler(&ip_vs_rr_scheduler);
 109 }
 110
 111 module_init(ip_vs_rr_init);
 112 module_exit(ip_vs_rr_cleanup);
 113 MODULE_LICENSE("GPL");