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![Christoph Hellwig](/assets/img/avatar_default.png)
Just let the one caller that wants optional WQ_HIGHPRI handling allocate a separate btrfs_workqueue for that. This allows to rename struct __btrfs_workqueue to btrfs_workqueue, remove a pointer indirection and separate allocation for all btrfs_workqueue users and generally simplify the code. Reviewed-by: Qu Wenruo <wqu@suse.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
341 lines
9 KiB
C
341 lines
9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2007 Oracle. All rights reserved.
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* Copyright (C) 2014 Fujitsu. All rights reserved.
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*/
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#include <linux/kthread.h>
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#include <linux/slab.h>
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#include <linux/list.h>
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#include <linux/spinlock.h>
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#include <linux/freezer.h>
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#include "async-thread.h"
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#include "ctree.h"
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enum {
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WORK_DONE_BIT,
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WORK_ORDER_DONE_BIT,
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};
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#define NO_THRESHOLD (-1)
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#define DFT_THRESHOLD (32)
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struct btrfs_workqueue {
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struct workqueue_struct *normal_wq;
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/* File system this workqueue services */
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struct btrfs_fs_info *fs_info;
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/* List head pointing to ordered work list */
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struct list_head ordered_list;
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/* Spinlock for ordered_list */
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spinlock_t list_lock;
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/* Thresholding related variants */
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atomic_t pending;
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/* Up limit of concurrency workers */
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int limit_active;
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/* Current number of concurrency workers */
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int current_active;
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/* Threshold to change current_active */
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int thresh;
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unsigned int count;
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spinlock_t thres_lock;
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};
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struct btrfs_fs_info * __pure btrfs_workqueue_owner(const struct btrfs_workqueue *wq)
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{
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return wq->fs_info;
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}
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struct btrfs_fs_info * __pure btrfs_work_owner(const struct btrfs_work *work)
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{
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return work->wq->fs_info;
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}
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bool btrfs_workqueue_normal_congested(const struct btrfs_workqueue *wq)
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{
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/*
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* We could compare wq->pending with num_online_cpus()
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* to support "thresh == NO_THRESHOLD" case, but it requires
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* moving up atomic_inc/dec in thresh_queue/exec_hook. Let's
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* postpone it until someone needs the support of that case.
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*/
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if (wq->thresh == NO_THRESHOLD)
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return false;
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return atomic_read(&wq->pending) > wq->thresh * 2;
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}
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struct btrfs_workqueue *btrfs_alloc_workqueue(struct btrfs_fs_info *fs_info,
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const char *name, unsigned int flags,
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int limit_active, int thresh)
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{
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struct btrfs_workqueue *ret = kzalloc(sizeof(*ret), GFP_KERNEL);
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if (!ret)
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return NULL;
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ret->fs_info = fs_info;
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ret->limit_active = limit_active;
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atomic_set(&ret->pending, 0);
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if (thresh == 0)
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thresh = DFT_THRESHOLD;
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/* For low threshold, disabling threshold is a better choice */
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if (thresh < DFT_THRESHOLD) {
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ret->current_active = limit_active;
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ret->thresh = NO_THRESHOLD;
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} else {
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/*
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* For threshold-able wq, let its concurrency grow on demand.
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* Use minimal max_active at alloc time to reduce resource
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* usage.
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*/
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ret->current_active = 1;
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ret->thresh = thresh;
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}
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ret->normal_wq = alloc_workqueue("btrfs-%s", flags, ret->current_active,
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name);
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if (!ret->normal_wq) {
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kfree(ret);
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return NULL;
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}
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INIT_LIST_HEAD(&ret->ordered_list);
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spin_lock_init(&ret->list_lock);
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spin_lock_init(&ret->thres_lock);
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trace_btrfs_workqueue_alloc(ret, name);
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return ret;
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}
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/*
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* Hook for threshold which will be called in btrfs_queue_work.
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* This hook WILL be called in IRQ handler context,
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* so workqueue_set_max_active MUST NOT be called in this hook
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*/
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static inline void thresh_queue_hook(struct btrfs_workqueue *wq)
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{
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if (wq->thresh == NO_THRESHOLD)
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return;
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atomic_inc(&wq->pending);
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}
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/*
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* Hook for threshold which will be called before executing the work,
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* This hook is called in kthread content.
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* So workqueue_set_max_active is called here.
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*/
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static inline void thresh_exec_hook(struct btrfs_workqueue *wq)
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{
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int new_current_active;
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long pending;
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int need_change = 0;
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if (wq->thresh == NO_THRESHOLD)
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return;
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atomic_dec(&wq->pending);
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spin_lock(&wq->thres_lock);
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/*
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* Use wq->count to limit the calling frequency of
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* workqueue_set_max_active.
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*/
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wq->count++;
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wq->count %= (wq->thresh / 4);
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if (!wq->count)
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goto out;
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new_current_active = wq->current_active;
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/*
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* pending may be changed later, but it's OK since we really
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* don't need it so accurate to calculate new_max_active.
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*/
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pending = atomic_read(&wq->pending);
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if (pending > wq->thresh)
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new_current_active++;
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if (pending < wq->thresh / 2)
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new_current_active--;
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new_current_active = clamp_val(new_current_active, 1, wq->limit_active);
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if (new_current_active != wq->current_active) {
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need_change = 1;
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wq->current_active = new_current_active;
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}
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out:
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spin_unlock(&wq->thres_lock);
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if (need_change) {
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workqueue_set_max_active(wq->normal_wq, wq->current_active);
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}
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}
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static void run_ordered_work(struct btrfs_workqueue *wq,
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struct btrfs_work *self)
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{
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struct list_head *list = &wq->ordered_list;
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struct btrfs_work *work;
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spinlock_t *lock = &wq->list_lock;
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unsigned long flags;
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bool free_self = false;
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while (1) {
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spin_lock_irqsave(lock, flags);
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if (list_empty(list))
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break;
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work = list_entry(list->next, struct btrfs_work,
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ordered_list);
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if (!test_bit(WORK_DONE_BIT, &work->flags))
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break;
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/*
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* Orders all subsequent loads after reading WORK_DONE_BIT,
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* paired with the smp_mb__before_atomic in btrfs_work_helper
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* this guarantees that the ordered function will see all
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* updates from ordinary work function.
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*/
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smp_rmb();
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/*
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* we are going to call the ordered done function, but
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* we leave the work item on the list as a barrier so
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* that later work items that are done don't have their
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* functions called before this one returns
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*/
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if (test_and_set_bit(WORK_ORDER_DONE_BIT, &work->flags))
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break;
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trace_btrfs_ordered_sched(work);
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spin_unlock_irqrestore(lock, flags);
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work->ordered_func(work);
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/* now take the lock again and drop our item from the list */
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spin_lock_irqsave(lock, flags);
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list_del(&work->ordered_list);
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spin_unlock_irqrestore(lock, flags);
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if (work == self) {
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/*
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* This is the work item that the worker is currently
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* executing.
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*
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* The kernel workqueue code guarantees non-reentrancy
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* of work items. I.e., if a work item with the same
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* address and work function is queued twice, the second
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* execution is blocked until the first one finishes. A
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* work item may be freed and recycled with the same
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* work function; the workqueue code assumes that the
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* original work item cannot depend on the recycled work
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* item in that case (see find_worker_executing_work()).
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*
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* Note that different types of Btrfs work can depend on
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* each other, and one type of work on one Btrfs
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* filesystem may even depend on the same type of work
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* on another Btrfs filesystem via, e.g., a loop device.
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* Therefore, we must not allow the current work item to
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* be recycled until we are really done, otherwise we
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* break the above assumption and can deadlock.
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*/
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free_self = true;
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} else {
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/*
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* We don't want to call the ordered free functions with
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* the lock held.
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*/
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work->ordered_free(work);
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/* NB: work must not be dereferenced past this point. */
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trace_btrfs_all_work_done(wq->fs_info, work);
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}
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}
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spin_unlock_irqrestore(lock, flags);
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if (free_self) {
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self->ordered_free(self);
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/* NB: self must not be dereferenced past this point. */
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trace_btrfs_all_work_done(wq->fs_info, self);
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}
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}
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static void btrfs_work_helper(struct work_struct *normal_work)
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{
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struct btrfs_work *work = container_of(normal_work, struct btrfs_work,
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normal_work);
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struct btrfs_workqueue *wq = work->wq;
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int need_order = 0;
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/*
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* We should not touch things inside work in the following cases:
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* 1) after work->func() if it has no ordered_free
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* Since the struct is freed in work->func().
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* 2) after setting WORK_DONE_BIT
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* The work may be freed in other threads almost instantly.
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* So we save the needed things here.
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*/
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if (work->ordered_func)
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need_order = 1;
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trace_btrfs_work_sched(work);
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thresh_exec_hook(wq);
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work->func(work);
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if (need_order) {
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/*
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* Ensures all memory accesses done in the work function are
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* ordered before setting the WORK_DONE_BIT. Ensuring the thread
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* which is going to executed the ordered work sees them.
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* Pairs with the smp_rmb in run_ordered_work.
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*/
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smp_mb__before_atomic();
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set_bit(WORK_DONE_BIT, &work->flags);
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run_ordered_work(wq, work);
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} else {
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/* NB: work must not be dereferenced past this point. */
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trace_btrfs_all_work_done(wq->fs_info, work);
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}
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}
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void btrfs_init_work(struct btrfs_work *work, btrfs_func_t func,
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btrfs_func_t ordered_func, btrfs_func_t ordered_free)
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{
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work->func = func;
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work->ordered_func = ordered_func;
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work->ordered_free = ordered_free;
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INIT_WORK(&work->normal_work, btrfs_work_helper);
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INIT_LIST_HEAD(&work->ordered_list);
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work->flags = 0;
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}
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void btrfs_queue_work(struct btrfs_workqueue *wq, struct btrfs_work *work)
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{
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unsigned long flags;
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work->wq = wq;
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thresh_queue_hook(wq);
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if (work->ordered_func) {
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spin_lock_irqsave(&wq->list_lock, flags);
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list_add_tail(&work->ordered_list, &wq->ordered_list);
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spin_unlock_irqrestore(&wq->list_lock, flags);
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}
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trace_btrfs_work_queued(work);
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queue_work(wq->normal_wq, &work->normal_work);
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}
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void btrfs_destroy_workqueue(struct btrfs_workqueue *wq)
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{
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if (!wq)
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return;
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destroy_workqueue(wq->normal_wq);
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trace_btrfs_workqueue_destroy(wq);
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kfree(wq);
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}
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void btrfs_workqueue_set_max(struct btrfs_workqueue *wq, int limit_active)
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{
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if (wq)
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wq->limit_active = limit_active;
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}
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void btrfs_flush_workqueue(struct btrfs_workqueue *wq)
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{
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flush_workqueue(wq->normal_wq);
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}
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