v4.19.13 snapshot.
diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c
new file mode 100644
index 0000000..d522494
--- /dev/null
+++ b/fs/btrfs/async-thread.c
@@ -0,0 +1,404 @@
+// 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"
+
+#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;
+
+ /* 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_workqueue {
+ struct __btrfs_workqueue *normal;
+ struct __btrfs_workqueue *high;
+};
+
+static void normal_work_helper(struct btrfs_work *work);
+
+#define BTRFS_WORK_HELPER(name) \
+noinline_for_stack void btrfs_##name(struct work_struct *arg) \
+{ \
+ struct btrfs_work *work = container_of(arg, struct btrfs_work, \
+ normal_work); \
+ normal_work_helper(work); \
+}
+
+struct btrfs_fs_info *
+btrfs_workqueue_owner(const struct __btrfs_workqueue *wq)
+{
+ return wq->fs_info;
+}
+
+struct btrfs_fs_info *
+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->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(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;
+ }
+
+ 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(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->normal = __btrfs_alloc_workqueue(fs_info, name,
+ flags & ~WQ_HIGHPRI,
+ limit_active, thresh);
+ if (!ret->normal) {
+ kfree(ret);
+ return NULL;
+ }
+
+ if (flags & WQ_HIGHPRI) {
+ ret->high = __btrfs_alloc_workqueue(fs_info, 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) {
+ void *wtag;
+
+ 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. Save the work as tag for the trace event,
+ * because the callback could free the structure.
+ */
+ wtag = work;
+ work->ordered_free(work);
+ trace_btrfs_all_work_done(wq->fs_info, wtag);
+ }
+ spin_unlock_irqrestore(lock, flags);
+}
+
+static void normal_work_helper(struct btrfs_work *work)
+{
+ struct __btrfs_workqueue *wq;
+ void *wtag;
+ 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;
+ /* Safe for tracepoints in case work gets freed by the callback */
+ wtag = work;
+
+ 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(wq->fs_info, wtag);
+}
+
+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);
+}