/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2011, 2012, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * lustre/ptlrpc/sec_gc.c
 *
 * Author: Eric Mei <ericm@clusterfs.com>
 */

#define DEBUG_SUBSYSTEM S_SEC

#include "../../include/linux/libcfs/libcfs.h"

#include "../include/obd_support.h"
#include "../include/obd_class.h"
#include "../include/lustre_net.h"
#include "../include/lustre_sec.h"

#include "ptlrpc_internal.h"

#define SEC_GC_INTERVAL (30 * 60)

static struct mutex sec_gc_mutex;
static LIST_HEAD(sec_gc_list);
static spinlock_t sec_gc_list_lock;

static LIST_HEAD(sec_gc_ctx_list);
static spinlock_t sec_gc_ctx_list_lock;

static struct ptlrpc_thread sec_gc_thread;
static atomic_t sec_gc_wait_del = ATOMIC_INIT(0);

void sptlrpc_gc_add_sec(struct ptlrpc_sec *sec)
{
        LASSERT(sec->ps_policy->sp_cops->gc_ctx);
        LASSERT(sec->ps_gc_interval > 0);
        LASSERT(list_empty(&sec->ps_gc_list));

        sec->ps_gc_next = ktime_get_real_seconds() + sec->ps_gc_interval;

        spin_lock(&sec_gc_list_lock);
        list_add_tail(&sec_gc_list, &sec->ps_gc_list);
        spin_unlock(&sec_gc_list_lock);

        CDEBUG(D_SEC, "added sec %p(%s)\n", sec, sec->ps_policy->sp_name);
}
EXPORT_SYMBOL(sptlrpc_gc_add_sec);

void sptlrpc_gc_del_sec(struct ptlrpc_sec *sec)
{
        if (list_empty(&sec->ps_gc_list))
                return;

        might_sleep();

        /* signal before list_del to make iteration in gc thread safe */
        atomic_inc(&sec_gc_wait_del);

        spin_lock(&sec_gc_list_lock);
        list_del_init(&sec->ps_gc_list);
        spin_unlock(&sec_gc_list_lock);

        /* barrier */
        mutex_lock(&sec_gc_mutex);
        mutex_unlock(&sec_gc_mutex);

        atomic_dec(&sec_gc_wait_del);

        CDEBUG(D_SEC, "del sec %p(%s)\n", sec, sec->ps_policy->sp_name);
}
EXPORT_SYMBOL(sptlrpc_gc_del_sec);

static void sec_process_ctx_list(void)
{
        struct ptlrpc_cli_ctx *ctx;

        spin_lock(&sec_gc_ctx_list_lock);

        while (!list_empty(&sec_gc_ctx_list)) {
                ctx = list_entry(sec_gc_ctx_list.next,
                                 struct ptlrpc_cli_ctx, cc_gc_chain);
                list_del_init(&ctx->cc_gc_chain);
                spin_unlock(&sec_gc_ctx_list_lock);

                LASSERT(ctx->cc_sec);
                LASSERT(atomic_read(&ctx->cc_refcount) == 1);
                CDEBUG(D_SEC, "gc pick up ctx %p(%u->%s)\n",
                       ctx, ctx->cc_vcred.vc_uid, sec2target_str(ctx->cc_sec));
                sptlrpc_cli_ctx_put(ctx, 1);

                spin_lock(&sec_gc_ctx_list_lock);
        }

        spin_unlock(&sec_gc_ctx_list_lock);
}

static void sec_do_gc(struct ptlrpc_sec *sec)
{
        LASSERT(sec->ps_policy->sp_cops->gc_ctx);

        if (unlikely(sec->ps_gc_next == 0)) {
                CDEBUG(D_SEC, "sec %p(%s) has 0 gc time\n",
                       sec, sec->ps_policy->sp_name);
                return;
        }

        CDEBUG(D_SEC, "check on sec %p(%s)\n", sec, sec->ps_policy->sp_name);

        if (sec->ps_gc_next > ktime_get_real_seconds())
                return;

        sec->ps_policy->sp_cops->gc_ctx(sec);
        sec->ps_gc_next = ktime_get_real_seconds() + sec->ps_gc_interval;
}

static int sec_gc_main(void *arg)
{
        struct ptlrpc_thread *thread = arg;
        struct l_wait_info lwi;

        unshare_fs_struct();

        /* Record that the thread is running */
        thread_set_flags(thread, SVC_RUNNING);
        wake_up(&thread->t_ctl_waitq);

        while (1) {
                struct ptlrpc_sec *sec;

                thread_clear_flags(thread, SVC_SIGNAL);
                sec_process_ctx_list();
again:
                /* go through sec list do gc.
                 * FIXME here we iterate through the whole list each time which
                 * is not optimal. we perhaps want to use balanced binary tree
                 * to trace each sec as order of expiry time.
                 * another issue here is we wakeup as fixed interval instead of
                 * according to each sec's expiry time
                 */
                mutex_lock(&sec_gc_mutex);
                list_for_each_entry(sec, &sec_gc_list, ps_gc_list) {
                        /* if someone is waiting to be deleted, let it
                         * proceed as soon as possible.
                         */
                        if (atomic_read(&sec_gc_wait_del)) {
                                CDEBUG(D_SEC, "deletion pending, start over\n");
                                mutex_unlock(&sec_gc_mutex);
                                goto again;
                        }

                        sec_do_gc(sec);
                }
                mutex_unlock(&sec_gc_mutex);

                /* check ctx list again before sleep */
                sec_process_ctx_list();

                lwi = LWI_TIMEOUT(SEC_GC_INTERVAL * HZ, NULL, NULL);
                l_wait_event(thread->t_ctl_waitq,
                             thread_is_stopping(thread) ||
                             thread_is_signal(thread),
                             &lwi);

                if (thread_test_and_clear_flags(thread, SVC_STOPPING))
                        break;
        }

        thread_set_flags(thread, SVC_STOPPED);
        wake_up(&thread->t_ctl_waitq);
        return 0;
}

int sptlrpc_gc_init(void)
{
        struct l_wait_info lwi = { 0 };
        struct task_struct *task;

        mutex_init(&sec_gc_mutex);
        spin_lock_init(&sec_gc_list_lock);
        spin_lock_init(&sec_gc_ctx_list_lock);

        /* initialize thread control */
        memset(&sec_gc_thread, 0, sizeof(sec_gc_thread));
        init_waitqueue_head(&sec_gc_thread.t_ctl_waitq);

        task = kthread_run(sec_gc_main, &sec_gc_thread, "sptlrpc_gc");
        if (IS_ERR(task)) {
                CERROR("can't start gc thread: %ld\n", PTR_ERR(task));
                return PTR_ERR(task);
        }

        l_wait_event(sec_gc_thread.t_ctl_waitq,
                     thread_is_running(&sec_gc_thread), &lwi);
        return 0;
}

void sptlrpc_gc_fini(void)
{
        struct l_wait_info lwi = { 0 };

        thread_set_flags(&sec_gc_thread, SVC_STOPPING);
        wake_up(&sec_gc_thread.t_ctl_waitq);

        l_wait_event(sec_gc_thread.t_ctl_waitq,
                     thread_is_stopped(&sec_gc_thread), &lwi);
}