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/*

 * 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 1.1.1.1 2004-04-15 01:13:59 phoenix 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/sched.h>

#include <linux/spinlock.h>

#include <asm/softirq.h>                /* for local_bh_* */

#include <asm/string.h>

#include <linux/kmod.h>

#include <net/ip_vs.h>

/*

 *  IPVS scheduler list

 */

static LIST_HEAD(ip_vs_schedulers);

/* lock for service table */

static rwlock_t __ip_vs_sched_lock = RW_LOCK_UNLOCKED;

/*

 *  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;

        struct list_head *l, *e;

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

                  sched_name);

        l = &ip_vs_schedulers;

        read_lock_bh(&__ip_vs_sched_lock);

        for (e=l->next; e!=l; e=e->next) {

                sched = list_entry(e, struct ip_vs_scheduler, n_list);

                /*

                 * Test and MOD_INC_USE_COUNT atomically

                 */

                if (sched->module && !try_inc_mod_count(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)

                        __MOD_DEC_USE_COUNT(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) {

                char module_name[IP_VS_SCHEDNAME_MAXLEN+8];

                sprintf(module_name,"ip_vs_%s", sched_name);

                request_module(module_name);

                sched = ip_vs_sched_getbyname(sched_name);

        }

        return sched;

}

void ip_vs_scheduler_put(struct ip_vs_scheduler *scheduler)

{

        if (scheduler->module)

                __MOD_DEC_USE_COUNT(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;

        }

        MOD_INC_USE_COUNT;

        /*

         *  Make sure that the scheduler with this name doesn't exist

         *  in the scheduler list.

         */

        sched = ip_vs_sched_getbyname(scheduler->name);

        if (sched) {

                ip_vs_scheduler_put(sched);

                MOD_DEC_USE_COUNT;

                IP_VS_ERR("register_ip_vs_scheduler(): [%s] scheduler "

                          "already existed in the system\n", scheduler->name);

                return -EINVAL;

        }

        write_lock_bh(&__ip_vs_sched_lock);

        if (scheduler->n_list.next != &scheduler->n_list) {

                write_unlock_bh(&__ip_vs_sched_lock);

                MOD_DEC_USE_COUNT;

                IP_VS_ERR("register_ip_vs_scheduler(): [%s] scheduler "

                          "already linked\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);

        MOD_DEC_USE_COUNT;

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

        return 0;

}