fs/btrfs/async-thread.c - kernel/bruno - Git at Google

 /*
  * 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;

 	/* 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_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);					\
 }

 bool btrfs_workqueue_normal_congested(struct btrfs_workqueue *wq)
 {
 	/*
 	 * We could compare wq->normal->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->normal->thresh == NO_THRESHOLD)
 		return false;

 	return atomic_read(&wq->normal->pending) > wq->normal->thresh * 2;
 }

 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 limit_active,
 			 int thresh)
 {
 	struct __btrfs_workqueue *ret = kzalloc(sizeof(*ret), GFP_NOFS);

 	if (!ret)
 		return NULL;

 	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;
 	}

 	if (flags & WQ_HIGHPRI)
 		ret->normal_wq = alloc_workqueue("%s-%s-high", flags,
 						 ret->current_active, "btrfs",
 						 name);
 	else
 		ret->normal_wq = alloc_workqueue("%s-%s", flags,
 						 ret->current_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 limit_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,
 					      limit_active, thresh);
 	if (!ret->normal) {
 		kfree(ret);
 		return NULL;
 	}

 	if (flags & WQ_HIGHPRI) {
 		ret->high = __btrfs_alloc_workqueue(name, flags, limit_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_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 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);
 	}
 	trace_btrfs_work_queued(work);
 	queue_work(wq->normal_wq, &work->normal_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 limit_active)
 {
 	if (!wq)
 		return;
 	wq->normal->limit_active = limit_active;
 	if (wq->high)
 		wq->high->limit_active = limit_active;
 }

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

	/* 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_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); \
	}

	bool btrfs_workqueue_normal_congested(struct btrfs_workqueue *wq)
	{
	/*
	* We could compare wq->normal->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->normal->thresh == NO_THRESHOLD)
	return false;

	return atomic_read(&wq->normal->pending) > wq->normal->thresh * 2;
	}

	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 limit_active,
	int thresh)
	{
	struct __btrfs_workqueue ret = kzalloc(sizeof(ret), GFP_NOFS);

	if (!ret)
	return NULL;

	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;
	}

	if (flags & WQ_HIGHPRI)
	ret->normal_wq = alloc_workqueue("%s-%s-high", flags,
	ret->current_active, "btrfs",
	name);
	else
	ret->normal_wq = alloc_workqueue("%s-%s", flags,
	ret->current_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 limit_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,
	limit_active, thresh);
	if (!ret->normal) {
	kfree(ret);
	return NULL;
	}

	if (flags & WQ_HIGHPRI) {
	ret->high = __btrfs_alloc_workqueue(name, flags, limit_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_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 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);
	}
	trace_btrfs_work_queued(work);
	queue_work(wq->normal_wq, &work->normal_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 limit_active)
	{
	if (!wq)
	return;
	wq->normal->limit_active = limit_active;
	if (wq->high)
	wq->high->limit_active = limit_active;
	}

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