/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 * Copyright (C) 2014 Fujitsu.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 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 for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/kthread.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/freezer.h>
#include "async-thread.h"
#include "ctree.h"

#define WORK_DONE_BIT 0
#define WORK_ORDER_DONE_BIT 1
#define WORK_HIGH_PRIO_BIT 2

#define NO_THRESHOLD (-1)
#define DFT_THRESHOLD (32)

struct __btrfs_workqueue {
        struct workqueue_struct *normal_wq;
        /* List head pointing to ordered work list */
        struct list_head ordered_list;

        /* Spinlock for ordered_list */
        spinlock_t list_lock;

        /* Thresholding related variants */
        atomic_t pending;
        int max_active;
        int current_max;
        int thresh;
        unsigned int count;
        spinlock_t thres_lock;
};

struct btrfs_workqueue {
        struct __btrfs_workqueue *normal;
        struct __btrfs_workqueue *high;
};

static void normal_work_helper(struct btrfs_work *work);

#define BTRFS_WORK_HELPER(name)                                 \
void btrfs_##name(struct work_struct *arg)                              \
{                                                                       \
        struct btrfs_work *work = container_of(arg, struct btrfs_work,  \
                                               normal_work);            \
        normal_work_helper(work);                                       \
}

BTRFS_WORK_HELPER(worker_helper);
BTRFS_WORK_HELPER(delalloc_helper);
BTRFS_WORK_HELPER(flush_delalloc_helper);
BTRFS_WORK_HELPER(cache_helper);
BTRFS_WORK_HELPER(submit_helper);
BTRFS_WORK_HELPER(fixup_helper);
BTRFS_WORK_HELPER(endio_helper);
BTRFS_WORK_HELPER(endio_meta_helper);
BTRFS_WORK_HELPER(endio_meta_write_helper);
BTRFS_WORK_HELPER(endio_raid56_helper);
BTRFS_WORK_HELPER(endio_repair_helper);
BTRFS_WORK_HELPER(rmw_helper);
BTRFS_WORK_HELPER(endio_write_helper);
BTRFS_WORK_HELPER(freespace_write_helper);
BTRFS_WORK_HELPER(delayed_meta_helper);
BTRFS_WORK_HELPER(readahead_helper);
BTRFS_WORK_HELPER(qgroup_rescan_helper);
BTRFS_WORK_HELPER(extent_refs_helper);
BTRFS_WORK_HELPER(scrub_helper);
BTRFS_WORK_HELPER(scrubwrc_helper);
BTRFS_WORK_HELPER(scrubnc_helper);
BTRFS_WORK_HELPER(scrubparity_helper);

static struct __btrfs_workqueue *
__btrfs_alloc_workqueue(const char *name, unsigned int flags, int max_active,
                         int thresh)
{
        struct __btrfs_workqueue *ret = kzalloc(sizeof(*ret), GFP_NOFS);

        if (!ret)
                return NULL;

        ret->max_active = max_active;
        atomic_set(&ret->pending, 0);
        if (thresh == 0)
                thresh = DFT_THRESHOLD;
        /* For low threshold, disabling threshold is a better choice */
        if (thresh < DFT_THRESHOLD) {
                ret->current_max = max_active;
                ret->thresh = NO_THRESHOLD;
        } else {
                ret->current_max = 1;
                ret->thresh = thresh;
        }

        if (flags & WQ_HIGHPRI)
                ret->normal_wq = alloc_workqueue("%s-%s-high", flags,
                                                 ret->max_active,
                                                 "btrfs", name);
        else
                ret->normal_wq = alloc_workqueue("%s-%s", flags,
                                                 ret->max_active, "btrfs",
                                                 name);
        if (!ret->normal_wq) {
                kfree(ret);
                return NULL;
        }

        INIT_LIST_HEAD(&ret->ordered_list);
        spin_lock_init(&ret->list_lock);
        spin_lock_init(&ret->thres_lock);
        trace_btrfs_workqueue_alloc(ret, name, flags & WQ_HIGHPRI);
        return ret;
}

static inline void
__btrfs_destroy_workqueue(struct __btrfs_workqueue *wq);

struct btrfs_workqueue *btrfs_alloc_workqueue(const char *name,
                                              unsigned int flags,
                                              int max_active,
                                              int thresh)
{
        struct btrfs_workqueue *ret = kzalloc(sizeof(*ret), GFP_NOFS);

        if (!ret)
                return NULL;

        ret->normal = __btrfs_alloc_workqueue(name, flags & ~WQ_HIGHPRI,
                                              max_active, thresh);
        if (!ret->normal) {
                kfree(ret);
                return NULL;
        }

        if (flags & WQ_HIGHPRI) {
                ret->high = __btrfs_alloc_workqueue(name, flags, max_active,
                                                    thresh);
                if (!ret->high) {
                        __btrfs_destroy_workqueue(ret->normal);
                        kfree(ret);
                        return NULL;
                }
        }
        return ret;
}

/*
 * Hook for threshold which will be called in btrfs_queue_work.
 * This hook WILL be called in IRQ handler context,
 * so workqueue_set_max_active MUST NOT be called in this hook
 */
static inline void thresh_queue_hook(struct __btrfs_workqueue *wq)
{
        if (wq->thresh == NO_THRESHOLD)
                return;
        atomic_inc(&wq->pending);
}

/*
 * Hook for threshold which will be called before executing the work,
 * This hook is called in kthread content.
 * So workqueue_set_max_active is called here.
 */
static inline void thresh_exec_hook(struct __btrfs_workqueue *wq)
{
        int new_max_active;
        long pending;
        int need_change = 0;

        if (wq->thresh == NO_THRESHOLD)
                return;

        atomic_dec(&wq->pending);
        spin_lock(&wq->thres_lock);
        /*
         * Use wq->count to limit the calling frequency of
         * workqueue_set_max_active.
         */
        wq->count++;
        wq->count %= (wq->thresh / 4);
        if (!wq->count)
                goto  out;
        new_max_active = wq->current_max;

        /*
         * pending may be changed later, but it's OK since we really
         * don't need it so accurate to calculate new_max_active.
         */
        pending = atomic_read(&wq->pending);
        if (pending > wq->thresh)
                new_max_active++;
        if (pending < wq->thresh / 2)
                new_max_active--;
        new_max_active = clamp_val(new_max_active, 1, wq->max_active);
        if (new_max_active != wq->current_max)  {
                need_change = 1;
                wq->current_max = new_max_active;
        }
out:
        spin_unlock(&wq->thres_lock);

        if (need_change) {
                workqueue_set_max_active(wq->normal_wq, wq->current_max);
        }
}

static void run_ordered_work(struct __btrfs_workqueue *wq)
{
        struct list_head *list = &wq->ordered_list;
        struct btrfs_work *work;
        spinlock_t *lock = &wq->list_lock;
        unsigned long flags;

        while (1) {
                spin_lock_irqsave(lock, flags);
                if (list_empty(list))
                        break;
                work = list_entry(list->next, struct btrfs_work,
                                  ordered_list);
                if (!test_bit(WORK_DONE_BIT, &work->flags))
                        break;

                /*
                 * we are going to call the ordered done function, but
                 * we leave the work item on the list as a barrier so
                 * that later work items that are done don't have their
                 * functions called before this one returns
                 */
                if (test_and_set_bit(WORK_ORDER_DONE_BIT, &work->flags))
                        break;
                trace_btrfs_ordered_sched(work);
                spin_unlock_irqrestore(lock, flags);
                work->ordered_func(work);

                /* now take the lock again and drop our item from the list */
                spin_lock_irqsave(lock, flags);
                list_del(&work->ordered_list);
                spin_unlock_irqrestore(lock, flags);

                /*
                 * we don't want to call the ordered free functions
                 * with the lock held though
                 */
                work->ordered_free(work);
                trace_btrfs_all_work_done(work);
        }
        spin_unlock_irqrestore(lock, flags);
}

static void normal_work_helper(struct btrfs_work *work)
{
        struct __btrfs_workqueue *wq;
        int need_order = 0;

        /*
         * We should not touch things inside work in the following cases:
         * 1) after work->func() if it has no ordered_free
         *    Since the struct is freed in work->func().
         * 2) after setting WORK_DONE_BIT
         *    The work may be freed in other threads almost instantly.
         * So we save the needed things here.
         */
        if (work->ordered_func)
                need_order = 1;
        wq = work->wq;

        trace_btrfs_work_sched(work);
        thresh_exec_hook(wq);
        work->func(work);
        if (need_order) {
                set_bit(WORK_DONE_BIT, &work->flags);
                run_ordered_work(wq);
        }
        if (!need_order)
                trace_btrfs_all_work_done(work);
}

void btrfs_init_work(struct btrfs_work *work, btrfs_work_func_t uniq_func,
                     btrfs_func_t func,
                     btrfs_func_t ordered_func,
                     btrfs_func_t ordered_free)
{
        work->func = func;
        work->ordered_func = ordered_func;
        work->ordered_free = ordered_free;
        INIT_WORK(&work->normal_work, uniq_func);
        INIT_LIST_HEAD(&work->ordered_list);
        work->flags = 0;
}

static inline void __btrfs_queue_work(struct __btrfs_workqueue *wq,
                                      struct btrfs_work *work)
{
        unsigned long flags;

        work->wq = wq;
        thresh_queue_hook(wq);
        if (work->ordered_func) {
                spin_lock_irqsave(&wq->list_lock, flags);
                list_add_tail(&work->ordered_list, &wq->ordered_list);
                spin_unlock_irqrestore(&wq->list_lock, flags);
        }
        queue_work(wq->normal_wq, &work->normal_work);
        trace_btrfs_work_queued(work);
}

void btrfs_queue_work(struct btrfs_workqueue *wq,
                      struct btrfs_work *work)
{
        struct __btrfs_workqueue *dest_wq;

        if (test_bit(WORK_HIGH_PRIO_BIT, &work->flags) && wq->high)
                dest_wq = wq->high;
        else
                dest_wq = wq->normal;
        __btrfs_queue_work(dest_wq, work);
}

static inline void
__btrfs_destroy_workqueue(struct __btrfs_workqueue *wq)
{
        destroy_workqueue(wq->normal_wq);
        trace_btrfs_workqueue_destroy(wq);
        kfree(wq);
}

void btrfs_destroy_workqueue(struct btrfs_workqueue *wq)
{
        if (!wq)
                return;
        if (wq->high)
                __btrfs_destroy_workqueue(wq->high);
        __btrfs_destroy_workqueue(wq->normal);
        kfree(wq);
}

void btrfs_workqueue_set_max(struct btrfs_workqueue *wq, int max)
{
        if (!wq)
                return;
        wq->normal->max_active = max;
        if (wq->high)
                wq->high->max_active = max;
}

void btrfs_set_work_high_priority(struct btrfs_work *work)
{
        set_bit(WORK_HIGH_PRIO_BIT, &work->flags);
}