// 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 DEFAULT_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_obj(*ret); 	if (!ret)		return NULL; 	btrfs_init_workqueue(ret, fs_info); 	ret->limit_active = limit_active;	if (thresh == 0)		thresh = DEFAULT_THRESHOLD;	/* For low threshold, disabling threshold is a better choice */	if (thresh < DEFAULT_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_obj(*ret);	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;	bool need_change = false; 	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 = true;		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_first_entry(list, 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;	bool need_order = false; 	/*	 * 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 = true; 	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);}