diff options
Diffstat (limited to 'fs/btrfs/async-thread.c')
-rw-r--r-- | fs/btrfs/async-thread.c | 254 |
1 files changed, 202 insertions, 52 deletions
diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c index 019e8af..282ca08 100644 --- a/fs/btrfs/async-thread.c +++ b/fs/btrfs/async-thread.c @@ -48,6 +48,9 @@ struct btrfs_worker_thread { /* number of things on the pending list */ atomic_t num_pending; + /* reference counter for this struct */ + atomic_t refs; + unsigned long sequence; /* protects the pending list. */ @@ -71,7 +74,12 @@ static void check_idle_worker(struct btrfs_worker_thread *worker) unsigned long flags; spin_lock_irqsave(&worker->workers->lock, flags); worker->idle = 1; - list_move(&worker->worker_list, &worker->workers->idle_list); + + /* the list may be empty if the worker is just starting */ + if (!list_empty(&worker->worker_list)) { + list_move(&worker->worker_list, + &worker->workers->idle_list); + } spin_unlock_irqrestore(&worker->workers->lock, flags); } } @@ -87,23 +95,49 @@ static void check_busy_worker(struct btrfs_worker_thread *worker) unsigned long flags; spin_lock_irqsave(&worker->workers->lock, flags); worker->idle = 0; - list_move_tail(&worker->worker_list, - &worker->workers->worker_list); + + if (!list_empty(&worker->worker_list)) { + list_move_tail(&worker->worker_list, + &worker->workers->worker_list); + } spin_unlock_irqrestore(&worker->workers->lock, flags); } } -static noinline int run_ordered_completions(struct btrfs_workers *workers, - struct btrfs_work *work) +static void check_pending_worker_creates(struct btrfs_worker_thread *worker) { + struct btrfs_workers *workers = worker->workers; unsigned long flags; + rmb(); + if (!workers->atomic_start_pending) + return; + + spin_lock_irqsave(&workers->lock, flags); + if (!workers->atomic_start_pending) + goto out; + + workers->atomic_start_pending = 0; + if (workers->num_workers >= workers->max_workers) + goto out; + + spin_unlock_irqrestore(&workers->lock, flags); + btrfs_start_workers(workers, 1); + return; + +out: + spin_unlock_irqrestore(&workers->lock, flags); +} + +static noinline int run_ordered_completions(struct btrfs_workers *workers, + struct btrfs_work *work) +{ if (!workers->ordered) return 0; set_bit(WORK_DONE_BIT, &work->flags); - spin_lock_irqsave(&workers->lock, flags); + spin_lock(&workers->order_lock); while (1) { if (!list_empty(&workers->prio_order_list)) { @@ -126,45 +160,118 @@ static noinline int run_ordered_completions(struct btrfs_workers *workers, if (test_and_set_bit(WORK_ORDER_DONE_BIT, &work->flags)) break; - spin_unlock_irqrestore(&workers->lock, flags); + spin_unlock(&workers->order_lock); work->ordered_func(work); /* now take the lock again and call the freeing code */ - spin_lock_irqsave(&workers->lock, flags); + spin_lock(&workers->order_lock); list_del(&work->order_list); work->ordered_free(work); } - spin_unlock_irqrestore(&workers->lock, flags); + spin_unlock(&workers->order_lock); return 0; } +static void put_worker(struct btrfs_worker_thread *worker) +{ + if (atomic_dec_and_test(&worker->refs)) + kfree(worker); +} + +static int try_worker_shutdown(struct btrfs_worker_thread *worker) +{ + int freeit = 0; + + spin_lock_irq(&worker->lock); + spin_lock(&worker->workers->lock); + if (worker->workers->num_workers > 1 && + worker->idle && + !worker->working && + !list_empty(&worker->worker_list) && + list_empty(&worker->prio_pending) && + list_empty(&worker->pending) && + atomic_read(&worker->num_pending) == 0) { + freeit = 1; + list_del_init(&worker->worker_list); + worker->workers->num_workers--; + } + spin_unlock(&worker->workers->lock); + spin_unlock_irq(&worker->lock); + + if (freeit) + put_worker(worker); + return freeit; +} + +static struct btrfs_work *get_next_work(struct btrfs_worker_thread *worker, + struct list_head *prio_head, + struct list_head *head) +{ + struct btrfs_work *work = NULL; + struct list_head *cur = NULL; + + if(!list_empty(prio_head)) + cur = prio_head->next; + + smp_mb(); + if (!list_empty(&worker->prio_pending)) + goto refill; + + if (!list_empty(head)) + cur = head->next; + + if (cur) + goto out; + +refill: + spin_lock_irq(&worker->lock); + list_splice_tail_init(&worker->prio_pending, prio_head); + list_splice_tail_init(&worker->pending, head); + + if (!list_empty(prio_head)) + cur = prio_head->next; + else if (!list_empty(head)) + cur = head->next; + spin_unlock_irq(&worker->lock); + + if (!cur) + goto out_fail; + +out: + work = list_entry(cur, struct btrfs_work, list); + +out_fail: + return work; +} + /* * main loop for servicing work items */ static int worker_loop(void *arg) { struct btrfs_worker_thread *worker = arg; - struct list_head *cur; + struct list_head head; + struct list_head prio_head; struct btrfs_work *work; + + INIT_LIST_HEAD(&head); + INIT_LIST_HEAD(&prio_head); + do { - spin_lock_irq(&worker->lock); -again_locked: +again: while (1) { - if (!list_empty(&worker->prio_pending)) - cur = worker->prio_pending.next; - else if (!list_empty(&worker->pending)) - cur = worker->pending.next; - else + + + work = get_next_work(worker, &prio_head, &head); + if (!work) break; - work = list_entry(cur, struct btrfs_work, list); list_del(&work->list); clear_bit(WORK_QUEUED_BIT, &work->flags); work->worker = worker; - spin_unlock_irq(&worker->lock); work->func(work); @@ -175,9 +282,13 @@ again_locked: */ run_ordered_completions(worker->workers, work); - spin_lock_irq(&worker->lock); - check_idle_worker(worker); + check_pending_worker_creates(worker); + } + + spin_lock_irq(&worker->lock); + check_idle_worker(worker); + if (freezing(current)) { worker->working = 0; spin_unlock_irq(&worker->lock); @@ -216,8 +327,10 @@ again_locked: spin_lock_irq(&worker->lock); set_current_state(TASK_INTERRUPTIBLE); if (!list_empty(&worker->pending) || - !list_empty(&worker->prio_pending)) - goto again_locked; + !list_empty(&worker->prio_pending)) { + spin_unlock_irq(&worker->lock); + goto again; + } /* * this makes sure we get a wakeup when someone @@ -226,8 +339,13 @@ again_locked: worker->working = 0; spin_unlock_irq(&worker->lock); - if (!kthread_should_stop()) - schedule(); + if (!kthread_should_stop()) { + schedule_timeout(HZ * 120); + if (!worker->working && + try_worker_shutdown(worker)) { + return 0; + } + } } __set_current_state(TASK_RUNNING); } @@ -242,16 +360,30 @@ int btrfs_stop_workers(struct btrfs_workers *workers) { struct list_head *cur; struct btrfs_worker_thread *worker; + int can_stop; + spin_lock_irq(&workers->lock); list_splice_init(&workers->idle_list, &workers->worker_list); while (!list_empty(&workers->worker_list)) { cur = workers->worker_list.next; worker = list_entry(cur, struct btrfs_worker_thread, worker_list); - kthread_stop(worker->task); - list_del(&worker->worker_list); - kfree(worker); + + atomic_inc(&worker->refs); + workers->num_workers -= 1; + if (!list_empty(&worker->worker_list)) { + list_del_init(&worker->worker_list); + put_worker(worker); + can_stop = 1; + } else + can_stop = 0; + spin_unlock_irq(&workers->lock); + if (can_stop) + kthread_stop(worker->task); + spin_lock_irq(&workers->lock); + put_worker(worker); } + spin_unlock_irq(&workers->lock); return 0; } @@ -266,10 +398,13 @@ void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max) INIT_LIST_HEAD(&workers->order_list); INIT_LIST_HEAD(&workers->prio_order_list); spin_lock_init(&workers->lock); + spin_lock_init(&workers->order_lock); workers->max_workers = max; workers->idle_thresh = 32; workers->name = name; workers->ordered = 0; + workers->atomic_start_pending = 0; + workers->atomic_worker_start = 0; } /* @@ -293,7 +428,9 @@ int btrfs_start_workers(struct btrfs_workers *workers, int num_workers) INIT_LIST_HEAD(&worker->prio_pending); INIT_LIST_HEAD(&worker->worker_list); spin_lock_init(&worker->lock); + atomic_set(&worker->num_pending, 0); + atomic_set(&worker->refs, 1); worker->workers = workers; worker->task = kthread_run(worker_loop, worker, "btrfs-%s-%d", workers->name, @@ -303,7 +440,6 @@ int btrfs_start_workers(struct btrfs_workers *workers, int num_workers) kfree(worker); goto fail; } - spin_lock_irq(&workers->lock); list_add_tail(&worker->worker_list, &workers->idle_list); worker->idle = 1; @@ -350,7 +486,6 @@ static struct btrfs_worker_thread *next_worker(struct btrfs_workers *workers) */ next = workers->worker_list.next; worker = list_entry(next, struct btrfs_worker_thread, worker_list); - atomic_inc(&worker->num_pending); worker->sequence++; if (worker->sequence % workers->idle_thresh == 0) @@ -367,28 +502,18 @@ static struct btrfs_worker_thread *find_worker(struct btrfs_workers *workers) { struct btrfs_worker_thread *worker; unsigned long flags; + struct list_head *fallback; again: spin_lock_irqsave(&workers->lock, flags); worker = next_worker(workers); - spin_unlock_irqrestore(&workers->lock, flags); if (!worker) { - spin_lock_irqsave(&workers->lock, flags); if (workers->num_workers >= workers->max_workers) { - struct list_head *fallback = NULL; - /* - * we have failed to find any workers, just - * return the force one - */ - if (!list_empty(&workers->worker_list)) - fallback = workers->worker_list.next; - if (!list_empty(&workers->idle_list)) - fallback = workers->idle_list.next; - BUG_ON(!fallback); - worker = list_entry(fallback, - struct btrfs_worker_thread, worker_list); - spin_unlock_irqrestore(&workers->lock, flags); + goto fallback; + } else if (workers->atomic_worker_start) { + workers->atomic_start_pending = 1; + goto fallback; } else { spin_unlock_irqrestore(&workers->lock, flags); /* we're below the limit, start another worker */ @@ -396,6 +521,28 @@ again: goto again; } } + goto found; + +fallback: + fallback = NULL; + /* + * we have failed to find any workers, just + * return the first one we can find. + */ + if (!list_empty(&workers->worker_list)) + fallback = workers->worker_list.next; + if (!list_empty(&workers->idle_list)) + fallback = workers->idle_list.next; + BUG_ON(!fallback); + worker = list_entry(fallback, + struct btrfs_worker_thread, worker_list); +found: + /* + * this makes sure the worker doesn't exit before it is placed + * onto a busy/idle list + */ + atomic_inc(&worker->num_pending); + spin_unlock_irqrestore(&workers->lock, flags); return worker; } @@ -427,7 +574,7 @@ int btrfs_requeue_work(struct btrfs_work *work) spin_lock(&worker->workers->lock); worker->idle = 0; list_move_tail(&worker->worker_list, - &worker->workers->worker_list); + &worker->workers->worker_list); spin_unlock(&worker->workers->lock); } if (!worker->working) { @@ -435,9 +582,9 @@ int btrfs_requeue_work(struct btrfs_work *work) worker->working = 1; } - spin_unlock_irqrestore(&worker->lock, flags); if (wake) wake_up_process(worker->task); + spin_unlock_irqrestore(&worker->lock, flags); out: return 0; @@ -463,14 +610,18 @@ int btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work) worker = find_worker(workers); if (workers->ordered) { - spin_lock_irqsave(&workers->lock, flags); + /* + * you're not allowed to do ordered queues from an + * interrupt handler + */ + spin_lock(&workers->order_lock); if (test_bit(WORK_HIGH_PRIO_BIT, &work->flags)) { list_add_tail(&work->order_list, &workers->prio_order_list); } else { list_add_tail(&work->order_list, &workers->order_list); } - spin_unlock_irqrestore(&workers->lock, flags); + spin_unlock(&workers->order_lock); } else { INIT_LIST_HEAD(&work->order_list); } @@ -481,7 +632,6 @@ int btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work) list_add_tail(&work->list, &worker->prio_pending); else list_add_tail(&work->list, &worker->pending); - atomic_inc(&worker->num_pending); check_busy_worker(worker); /* @@ -492,10 +642,10 @@ int btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work) wake = 1; worker->working = 1; - spin_unlock_irqrestore(&worker->lock, flags); - if (wake) wake_up_process(worker->task); + spin_unlock_irqrestore(&worker->lock, flags); + out: return 0; } |