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_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 *
  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
 117 static int __init ip_vs_rr_init(void)
 118 {
 119         return register_ip_vs_scheduler(&ip_vs_rr_scheduler);
 120 }
 121
 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");