diff options
Diffstat (limited to 'fs/btrfs/async-thread.c')
| -rw-r--r-- | fs/btrfs/async-thread.c | 81 |
1 files changed, 73 insertions, 8 deletions
diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c index 282ca085c2fb..c0861e781cdb 100644 --- a/fs/btrfs/async-thread.c +++ b/fs/btrfs/async-thread.c @@ -64,6 +64,51 @@ struct btrfs_worker_thread { }; /* + * btrfs_start_workers uses kthread_run, which can block waiting for memory + * for a very long time. It will actually throttle on page writeback, + * and so it may not make progress until after our btrfs worker threads + * process all of the pending work structs in their queue + * + * This means we can't use btrfs_start_workers from inside a btrfs worker + * thread that is used as part of cleaning dirty memory, which pretty much + * involves all of the worker threads. + * + * Instead we have a helper queue who never has more than one thread + * where we scheduler thread start operations. This worker_start struct + * is used to contain the work and hold a pointer to the queue that needs + * another worker. + */ +struct worker_start { + struct btrfs_work work; + struct btrfs_workers *queue; +}; + +static void start_new_worker_func(struct btrfs_work *work) +{ + struct worker_start *start; + start = container_of(work, struct worker_start, work); + btrfs_start_workers(start->queue, 1); + kfree(start); +} + +static int start_new_worker(struct btrfs_workers *queue) +{ + struct worker_start *start; + int ret; + + start = kzalloc(sizeof(*start), GFP_NOFS); + if (!start) + return -ENOMEM; + + start->work.func = start_new_worker_func; + start->queue = queue; + ret = btrfs_queue_worker(queue->atomic_worker_start, &start->work); + if (ret) + kfree(start); + return ret; +} + +/* * helper function to move a thread onto the idle list after it * has finished some requests. */ @@ -118,11 +163,13 @@ static void check_pending_worker_creates(struct btrfs_worker_thread *worker) goto out; workers->atomic_start_pending = 0; - if (workers->num_workers >= workers->max_workers) + if (workers->num_workers + workers->num_workers_starting >= + workers->max_workers) goto out; + workers->num_workers_starting += 1; spin_unlock_irqrestore(&workers->lock, flags); - btrfs_start_workers(workers, 1); + start_new_worker(workers); return; out: @@ -390,9 +437,11 @@ int btrfs_stop_workers(struct btrfs_workers *workers) /* * simple init on struct btrfs_workers */ -void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max) +void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max, + struct btrfs_workers *async_helper) { workers->num_workers = 0; + workers->num_workers_starting = 0; INIT_LIST_HEAD(&workers->worker_list); INIT_LIST_HEAD(&workers->idle_list); INIT_LIST_HEAD(&workers->order_list); @@ -404,14 +453,15 @@ void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max) workers->name = name; workers->ordered = 0; workers->atomic_start_pending = 0; - workers->atomic_worker_start = 0; + workers->atomic_worker_start = async_helper; } /* * starts new worker threads. This does not enforce the max worker * count in case you need to temporarily go past it. */ -int btrfs_start_workers(struct btrfs_workers *workers, int num_workers) +static int __btrfs_start_workers(struct btrfs_workers *workers, + int num_workers) { struct btrfs_worker_thread *worker; int ret = 0; @@ -444,6 +494,8 @@ int btrfs_start_workers(struct btrfs_workers *workers, int num_workers) list_add_tail(&worker->worker_list, &workers->idle_list); worker->idle = 1; workers->num_workers++; + workers->num_workers_starting--; + WARN_ON(workers->num_workers_starting < 0); spin_unlock_irq(&workers->lock); } return 0; @@ -452,6 +504,14 @@ fail: return ret; } +int btrfs_start_workers(struct btrfs_workers *workers, int num_workers) +{ + spin_lock_irq(&workers->lock); + workers->num_workers_starting += num_workers; + spin_unlock_irq(&workers->lock); + return __btrfs_start_workers(workers, num_workers); +} + /* * run through the list and find a worker thread that doesn't have a lot * to do right now. This can return null if we aren't yet at the thread @@ -461,7 +521,10 @@ static struct btrfs_worker_thread *next_worker(struct btrfs_workers *workers) { struct btrfs_worker_thread *worker; struct list_head *next; - int enforce_min = workers->num_workers < workers->max_workers; + int enforce_min; + + enforce_min = (workers->num_workers + workers->num_workers_starting) < + workers->max_workers; /* * if we find an idle thread, don't move it to the end of the @@ -509,15 +572,17 @@ again: worker = next_worker(workers); if (!worker) { - if (workers->num_workers >= workers->max_workers) { + if (workers->num_workers + workers->num_workers_starting >= + workers->max_workers) { goto fallback; } else if (workers->atomic_worker_start) { workers->atomic_start_pending = 1; goto fallback; } else { + workers->num_workers_starting++; spin_unlock_irqrestore(&workers->lock, flags); /* we're below the limit, start another worker */ - btrfs_start_workers(workers, 1); + __btrfs_start_workers(workers, 1); goto again; } } |