fs/btrfs/async-thread.c - linux - Git at Google

 // 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 "async-thread.h"
 #include "ctree.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;
 }

 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;

 	ret->fs_info = fs_info;
 	ret->limit_active = limit_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_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;
 	}

 	INIT_LIST_HEAD(&ret->ordered_list);
 	spin_lock_init(&ret->list_lock);
 	spin_lock_init(&ret->thres_lock);
 	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);

 		/* 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_free(work);
 			/* 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_free(self);
 		/* 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_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_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, 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);
 }
	// 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 "async-thread.h"
	#include "ctree.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;
	}

	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;

	ret->fs_info = fs_info;
	ret->limit_active = limit_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_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;
	}

	INIT_LIST_HEAD(&ret->ordered_list);
	spin_lock_init(&ret->list_lock);
	spin_lock_init(&ret->thres_lock);
	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);

	/* 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_free(work);
	/* 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_free(self);
	/* 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_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_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, 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);
	}