/*
* 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 <linux/workqueue.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 inline struct __btrfs_workqueue
*__btrfs_alloc_workqueue(const char *name, int flags, int max_active,
int thresh)
{
struct __btrfs_workqueue *ret = kzalloc(sizeof(*ret), GFP_NOFS);
if (unlikely(!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 (unlikely(!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,
int flags,
int max_active,
int thresh)
{
struct btrfs_workqueue *ret = kzalloc(sizeof(*ret), GFP_NOFS);
if (unlikely(!ret))
return NULL;
ret->normal = __btrfs_alloc_workqueue(name, flags & ~WQ_HIGHPRI,
max_active, thresh);
if (unlikely(!ret->normal)) {
kfree(ret);
return NULL;
}
if (flags & WQ_HIGHPRI) {
ret->high = __btrfs_alloc_workqueue(name, flags, max_active,
thresh);
if (unlikely(!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 work_struct *arg)
{
struct btrfs_work *work;
struct __btrfs_workqueue *wq;
int need_order = 0;
work = container_of(arg, struct btrfs_work, normal_work);
/*
* 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_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, normal_work_helper);
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);
}
