ip_vs_rr.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * IPVS:        Round-Robin Scheduling module
  4 *
  5 * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
  6 *              Peter Kese <peter.kese@ijs.si>
  7 *
  8 * Fixes/Changes:
  9 *     Wensong Zhang            :     changed the ip_vs_rr_schedule to return dest
 10 *     Julian Anastasov         :     fixed the NULL pointer access bug in debugging
 11 *     Wensong Zhang            :     changed some comestics things for debugging
 12 *     Wensong Zhang            :     changed for the d-linked destination list
 13 *     Wensong Zhang            :     added the ip_vs_rr_update_svc
 14 *     Wensong Zhang            :     added any dest with weight=0 is quiesced
 15 */
 16
 17#define pr_fmt(fmt) "IPVS: " fmt
 18
 19#include <linux/module.h>
 20#include <linux/kernel.h>
 21
 22#include <net/ip_vs.h>
 23
 24
 25static int ip_vs_rr_init_svc(struct ip_vs_service *svc)
 26{
 27	svc->sched_data = &svc->destinations;
 28	return 0;
 29}
 30
 31
 32static int ip_vs_rr_del_dest(struct ip_vs_service *svc, struct ip_vs_dest *dest)
 33{
 34	struct list_head *p;
 35
 36	spin_lock_bh(&svc->sched_lock);
 37	p = (struct list_head *) svc->sched_data;
 38	/* dest is already unlinked, so p->prev is not valid but
 39	 * p->next is valid, use it to reach previous entry.
 40	 */
 41	if (p == &dest->n_list)
 42		svc->sched_data = p->next->prev;
 43	spin_unlock_bh(&svc->sched_lock);
 44	return 0;
 45}
 46
 47
 48/*
 49 * Round-Robin Scheduling
 50 */
 51static struct ip_vs_dest *
 52ip_vs_rr_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
 53		  struct ip_vs_iphdr *iph)
 54{
 55	struct list_head *p;
 56	struct ip_vs_dest *dest, *last;
 57	int pass = 0;
 58
 59	IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
 60
 61	spin_lock_bh(&svc->sched_lock);
 62	p = (struct list_head *) svc->sched_data;
 63	last = dest = list_entry(p, struct ip_vs_dest, n_list);
 64
 65	do {
 66		list_for_each_entry_continue_rcu(dest,
 67						 &svc->destinations,
 68						 n_list) {
 69			if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
 70			    atomic_read(&dest->weight) > 0)
 71				/* HIT */
 72				goto out;
 73			if (dest == last)
 74				goto stop;
 75		}
 76		pass++;
 77		/* Previous dest could be unlinked, do not loop forever.
 78		 * If we stay at head there is no need for 2nd pass.
 79		 */
 80	} while (pass < 2 && p != &svc->destinations);
 81
 82stop:
 83	spin_unlock_bh(&svc->sched_lock);
 84	ip_vs_scheduler_err(svc, "no destination available");
 85	return NULL;
 86
 87  out:
 88	svc->sched_data = &dest->n_list;
 89	spin_unlock_bh(&svc->sched_lock);
 90	IP_VS_DBG_BUF(6, "RR: server %s:%u "
 91		      "activeconns %d refcnt %d weight %d\n",
 92		      IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port),
 93		      atomic_read(&dest->activeconns),
 94		      refcount_read(&dest->refcnt), atomic_read(&dest->weight));
 95
 96	return dest;
 97}
 98
 99
100static struct ip_vs_scheduler ip_vs_rr_scheduler = {
101	.name =			"rr",			/* name */
102	.refcnt =		ATOMIC_INIT(0),
103	.module =		THIS_MODULE,
104	.n_list =		LIST_HEAD_INIT(ip_vs_rr_scheduler.n_list),
105	.init_service =		ip_vs_rr_init_svc,
106	.add_dest =		NULL,
107	.del_dest =		ip_vs_rr_del_dest,
108	.schedule =		ip_vs_rr_schedule,
109};
110
111static int __init ip_vs_rr_init(void)
112{
113	return register_ip_vs_scheduler(&ip_vs_rr_scheduler);
114}
115
116static void __exit ip_vs_rr_cleanup(void)
117{
118	unregister_ip_vs_scheduler(&ip_vs_rr_scheduler);
119	synchronize_rcu();
120}
121
122module_init(ip_vs_rr_init);
123module_exit(ip_vs_rr_cleanup);
124MODULE_DESCRIPTION("ipvs round-robin scheduler");
125MODULE_LICENSE("GPL");