// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2007 Oracle. All rights reserved.
* Copyright (C) 2014 Fujitsu. All rights reserved.
*/
#include <linux/kthread.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/freezer.h>
#include <trace/events/btrfs.h>
#include "async-thread.h"
enum {
WORK_DONE_BIT,
WORK_ORDER_DONE_BIT,
};
#define NO_THRESHOLD (-1)
#define DFT_THRESHOLD (32)
struct btrfs_workqueue {
struct workqueue_struct *normal_wq;
/* File system this workqueue services */
struct btrfs_fs_info *fs_info;
/* 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;
/* Up limit of concurrency workers */
int limit_active;
/* Current number of concurrency workers */
int current_active;
/* Threshold to change current_active */
int thresh;
unsigned int count;
spinlock_t thres_lock;
};
struct btrfs_fs_info * __pure btrfs_workqueue_owner(const struct btrfs_workqueue *wq)
{
return wq->fs_info;
}
struct btrfs_fs_info * __pure btrfs_work_owner(const struct btrfs_work *work)
{
return work->wq->fs_info;
}
bool btrfs_workqueue_normal_congested(const struct btrfs_workqueue *wq)
{
/*
* We could compare wq->pending with num_online_cpus()
* to support "thresh == NO_THRESHOLD" case, but it requires
* moving up atomic_inc/dec in thresh_queue/exec_hook. Let's
* postpone it until someone needs the support of that case.
*/
if (wq->thresh == NO_THRESHOLD)
return false;
return atomic_read(&wq->pending) > wq->thresh * 2;
}
static void btrfs_init_workqueue(struct btrfs_workqueue *wq,
struct btrfs_fs_info *fs_info)
{
wq->fs_info = fs_info;
atomic_set(&wq->pending, 0);
INIT_LIST_HEAD(&wq->ordered_list);
spin_lock_init(&wq->list_lock);
spin_lock_init(&wq->thres_lock);
}
struct btrfs_workqueue *btrfs_alloc_workqueue(struct btrfs_fs_info *fs_info,
const char *name, unsigned int flags,
int limit_active, int thresh)
{
struct btrfs_workqueue *ret = kzalloc(sizeof(*ret), GFP_KERNEL);
if (!ret)
return NULL;
btrfs_init_workqueue(ret, fs_info);
ret->limit_active = limit_active;
if (thresh == 0)
thresh = DFT_THRESHOLD;
/* For low threshold, disabling threshold is a better choice */
if (thresh < DFT_THRESHOLD) {
ret->current_active = limit_active;
ret->thresh = NO_THRESHOLD;
} else {
/*
* For threshold-able wq, let its concurrency grow on demand.
* Use minimal max_active at alloc time to reduce resource
* usage.
*/
ret->current_active = 1;
ret->thresh = thresh;
}
ret->normal_wq = alloc_workqueue("btrfs-%s", flags, ret->current_active,
name);
if (!ret->normal_wq) {
kfree(ret);
return NULL;
}
trace_btrfs_workqueue_alloc(ret, name);
return ret;
}
struct btrfs_workqueue *btrfs_alloc_ordered_workqueue(
struct btrfs_fs_info *fs_info, const char *name,
unsigned int flags)
{
struct btrfs_workqueue *ret;
ret = kzalloc(sizeof(*ret), GFP_KERNEL);
if (!ret)
return NULL;
btrfs_init_workqueue(ret, fs_info);
/* Ordered workqueues don't allow @max_active adjustments. */
ret->limit_active = 1;
ret->current_active = 1;
ret->thresh = NO_THRESHOLD;
ret->normal_wq = alloc_ordered_workqueue("btrfs-%s", flags, name);
if (!ret->normal_wq) {
kfree(ret);
return NULL;
}
trace_btrfs_workqueue_alloc(ret, name);
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_current_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_current_active = wq->current_active;
/*
* 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_current_active++;
if (pending < wq->thresh / 2)
new_current_active--;
new_current_active = clamp_val(new_current_active, 1, wq->limit_active);
if (new_current_active != wq->current_active) {
need_change = 1;
wq->current_active = new_current_active;
}
out:
spin_unlock(&wq->thres_lock);
if (need_change) {
workqueue_set_max_active(wq->normal_wq, wq->current_active);
}
}
static void run_ordered_work(struct btrfs_workqueue *wq,
struct btrfs_work *self)
{
struct list_head *list = &wq->ordered_list;
struct btrfs_work *work;
spinlock_t *lock = &wq->list_lock;
unsigned long flags;
bool free_self = false;
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;
/*
* Orders all subsequent loads after reading WORK_DONE_BIT,
* paired with the smp_mb__before_atomic in btrfs_work_helper
* this guarantees that the ordered function will see all
* updates from ordinary work function.
*/
smp_rmb();
/*
* 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, false);
/* 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);
if (work == self) {
/*
* This is the work item that the worker is currently
* executing.
*
* The kernel workqueue code guarantees non-reentrancy
* of work items. I.e., if a work item with the same
* address and work function is queued twice, the second
* execution is blocked until the first one finishes. A
* work item may be freed and recycled with the same
* work function; the workqueue code assumes that the
* original work item cannot depend on the recycled work
* item in that case (see find_worker_executing_work()).
*
* Note that different types of Btrfs work can depend on
* each other, and one type of work on one Btrfs
* filesystem may even depend on the same type of work
* on another Btrfs filesystem via, e.g., a loop device.
* Therefore, we must not allow the current work item to
* be recycled until we are really done, otherwise we
* break the above assumption and can deadlock.
*/
free_self = true;
} else {
/*
* We don't want to call the ordered free functions with
* the lock held.
*/
work->ordered_func(work, true);
/* NB: work must not be dereferenced past this point. */
trace_btrfs_all_work_done(wq->fs_info, work);
}
}
spin_unlock_irqrestore(lock, flags);
if (free_self) {
self->ordered_func(self, true);
/* NB: self must not be dereferenced past this point. */
trace_btrfs_all_work_done(wq->fs_info, self);
}
}
static void btrfs_work_helper(struct work_struct *normal_work)
{
struct btrfs_work *work = container_of(normal_work, struct btrfs_work,
normal_work);
struct btrfs_workqueue *wq = work->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_func(..., true) to 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;
trace_btrfs_work_sched(work);
thresh_exec_hook(wq);
work->func(work);
if (need_order) {
/*
* Ensures all memory accesses done in the work function are
* ordered before setting the WORK_DONE_BIT. Ensuring the thread
* which is going to executed the ordered work sees them.
* Pairs with the smp_rmb in run_ordered_work.
*/
smp_mb__before_atomic();
set_bit(WORK_DONE_BIT, &work->flags);
run_ordered_work(wq, work);
} else {
/* NB: work must not be dereferenced past this point. */
trace_btrfs_all_work_done(wq->fs_info, work);
}
}
void btrfs_init_work(struct btrfs_work *work, btrfs_func_t func,
btrfs_ordered_func_t ordered_func)
{
work->func = func;
work->ordered_func = ordered_func;
INIT_WORK(&work->normal_work, btrfs_work_helper);
INIT_LIST_HEAD(&work->ordered_list);
work->flags = 0;
}
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);
}
trace_btrfs_work_queued(work);
queue_work(wq->normal_wq, &work->normal_work);
}
void btrfs_destroy_workqueue(struct btrfs_workqueue *wq)
{
if (!wq)
return;
destroy_workqueue(wq->normal_wq);
trace_btrfs_workqueue_destroy(wq);
kfree(wq);
}
void btrfs_workqueue_set_max(struct btrfs_workqueue *wq, int limit_active)
{
if (wq)
wq->limit_active = limit_active;
}
void btrfs_flush_workqueue(struct btrfs_workqueue *wq)
{
flush_workqueue(wq->normal_wq);
}
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