/*
 * IPVS         An implementation of the IP virtual server support for the
 *              LINUX operating system.  IPVS is now implemented as a module
 *              over the Netfilter framework. IPVS can be used to build a
 *              high-performance and highly available server based on a
 *              cluster of servers.
 *
 * Version:     $Id: ip_vs_sched.c,v 1.13 2003/05/10 03:05:23 wensong Exp $
 *
 * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
 *              Peter Kese <peter.kese@ijs.si>
 *
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 *
 * Changes:
 *
 */

#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <asm/string.h>
#include <linux/kmod.h>
#include <linux/sysctl.h>

#include <net/ip_vs.h>

/*
 *  IPVS scheduler list
 */
static LIST_HEAD(ip_vs_schedulers);

/* lock for service table */
static DEFINE_RWLOCK(__ip_vs_sched_lock);


/*
 *  Bind a service with a scheduler
 */
int ip_vs_bind_scheduler(struct ip_vs_service *svc,
                         struct ip_vs_scheduler *scheduler)
{
        int ret;

        if (svc == NULL) {
                IP_VS_ERR("ip_vs_bind_scheduler(): svc arg NULL\n");
                return -EINVAL;
        }
        if (scheduler == NULL) {
                IP_VS_ERR("ip_vs_bind_scheduler(): scheduler arg NULL\n");
                return -EINVAL;
        }

        svc->scheduler = scheduler;

        if (scheduler->init_service) {
                ret = scheduler->init_service(svc);
                if (ret) {
                        IP_VS_ERR("ip_vs_bind_scheduler(): init error\n");
                        return ret;
                }
        }

        return 0;
}


/*
 *  Unbind a service with its scheduler
 */
int ip_vs_unbind_scheduler(struct ip_vs_service *svc)
{
        struct ip_vs_scheduler *sched;

        if (svc == NULL) {
                IP_VS_ERR("ip_vs_unbind_scheduler(): svc arg NULL\n");
                return -EINVAL;
        }

        sched = svc->scheduler;
        if (sched == NULL) {
                IP_VS_ERR("ip_vs_unbind_scheduler(): svc isn't bound\n");
                return -EINVAL;
        }

        if (sched->done_service) {
                if (sched->done_service(svc) != 0) {
                        IP_VS_ERR("ip_vs_unbind_scheduler(): done error\n");
                        return -EINVAL;
                }
        }

        svc->scheduler = NULL;
        return 0;
}


/*
 *  Get scheduler in the scheduler list by name
 */
static struct ip_vs_scheduler *ip_vs_sched_getbyname(const char *sched_name)
{
        struct ip_vs_scheduler *sched;

        IP_VS_DBG(2, "ip_vs_sched_getbyname(): sched_name \"%s\"\n",
                  sched_name);

        read_lock_bh(&__ip_vs_sched_lock);

        list_for_each_entry(sched, &ip_vs_schedulers, n_list) {
                /*
                 * Test and get the modules atomically
                 */
                if (sched->module && !try_module_get(sched->module)) {
                        /*
                         * This scheduler is just deleted
                         */
                        continue;
                }
                if (strcmp(sched_name, sched->name)==0) {
                        /* HIT */
                        read_unlock_bh(&__ip_vs_sched_lock);
                        return sched;
                }
                if (sched->module)
                        module_put(sched->module);
        }

        read_unlock_bh(&__ip_vs_sched_lock);
        return NULL;
}


/*
 *  Lookup scheduler and try to load it if it doesn't exist
 */
struct ip_vs_scheduler *ip_vs_scheduler_get(const char *sched_name)
{
        struct ip_vs_scheduler *sched;

        /*
         *  Search for the scheduler by sched_name
         */
        sched = ip_vs_sched_getbyname(sched_name);

        /*
         *  If scheduler not found, load the module and search again
         */
        if (sched == NULL) {
                request_module("ip_vs_%s", sched_name);
                sched = ip_vs_sched_getbyname(sched_name);
        }

        return sched;
}

void ip_vs_scheduler_put(struct ip_vs_scheduler *scheduler)
{
        if (scheduler->module)
                module_put(scheduler->module);
}


/*
 *  Register a scheduler in the scheduler list
 */
int register_ip_vs_scheduler(struct ip_vs_scheduler *scheduler)
{
        struct ip_vs_scheduler *sched;

        if (!scheduler) {
                IP_VS_ERR("register_ip_vs_scheduler(): NULL arg\n");
                return -EINVAL;
        }

        if (!scheduler->name) {
                IP_VS_ERR("register_ip_vs_scheduler(): NULL scheduler_name\n");
                return -EINVAL;
        }

        /* increase the module use count */
        ip_vs_use_count_inc();

        write_lock_bh(&__ip_vs_sched_lock);

        if (scheduler->n_list.next != &scheduler->n_list) {
                write_unlock_bh(&__ip_vs_sched_lock);
                ip_vs_use_count_dec();
                IP_VS_ERR("register_ip_vs_scheduler(): [%s] scheduler "
                          "already linked\n", scheduler->name);
                return -EINVAL;
        }

        /*
         *  Make sure that the scheduler with this name doesn't exist
         *  in the scheduler list.
         */
        list_for_each_entry(sched, &ip_vs_schedulers, n_list) {
                if (strcmp(scheduler->name, sched->name) == 0) {
                        write_unlock_bh(&__ip_vs_sched_lock);
                        ip_vs_use_count_dec();
                        IP_VS_ERR("register_ip_vs_scheduler(): [%s] scheduler "
                                        "already existed in the system\n",
                                        scheduler->name);
                        return -EINVAL;
                }
        }
        /*
         *      Add it into the d-linked scheduler list
         */
        list_add(&scheduler->n_list, &ip_vs_schedulers);
        write_unlock_bh(&__ip_vs_sched_lock);

        IP_VS_INFO("[%s] scheduler registered.\n", scheduler->name);

        return 0;
}


/*
 *  Unregister a scheduler from the scheduler list
 */
int unregister_ip_vs_scheduler(struct ip_vs_scheduler *scheduler)
{
        if (!scheduler) {
                IP_VS_ERR( "unregister_ip_vs_scheduler(): NULL arg\n");
                return -EINVAL;
        }

        write_lock_bh(&__ip_vs_sched_lock);
        if (scheduler->n_list.next == &scheduler->n_list) {
                write_unlock_bh(&__ip_vs_sched_lock);
                IP_VS_ERR("unregister_ip_vs_scheduler(): [%s] scheduler "
                          "is not in the list. failed\n", scheduler->name);
                return -EINVAL;
        }

        /*
         *      Remove it from the d-linked scheduler list
         */
        list_del(&scheduler->n_list);
        write_unlock_bh(&__ip_vs_sched_lock);

        /* decrease the module use count */
        ip_vs_use_count_dec();

        IP_VS_INFO("[%s] scheduler unregistered.\n", scheduler->name);

        return 0;
}