io-wq: remove worker->wait waitqueue

We only have one cases of using the waitqueue to wake the worker, the
rest are using wake_up_process(). Since we can save some cycles not
fiddling with the waitqueue io_wqe_worker(), switch the work activation
to task wakeup and get rid of the now unused wait_queue_head_t in
struct io_worker.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io-wq.c

@@ -49,7 +49,6 @@ struct io_worker {
 	struct hlist_nulls_node nulls_node;
 	struct list_head all_list;
 	struct task_struct *task;
-	wait_queue_head_t wait;
 	struct io_wqe *wqe;
 
 	struct io_wq_work *cur_work;
@@ -258,7 +257,7 @@ static bool io_wqe_activate_free_worker(struct io_wqe *wqe)
 
 	worker = hlist_nulls_entry(n, struct io_worker, nulls_node);
 	if (io_worker_get(worker)) {
-		wake_up(&worker->wait);
+		wake_up_process(worker->task);
 		io_worker_release(worker);
 		return true;
 	}
@@ -497,13 +496,11 @@ static int io_wqe_worker(void *data)
 	struct io_worker *worker = data;
 	struct io_wqe *wqe = worker->wqe;
 	struct io_wq *wq = wqe->wq;
-	DEFINE_WAIT(wait);
 
 	io_worker_start(wqe, worker);
 
 	while (!test_bit(IO_WQ_BIT_EXIT, &wq->state)) {
-		prepare_to_wait(&worker->wait, &wait, TASK_INTERRUPTIBLE);
-
+		set_current_state(TASK_INTERRUPTIBLE);
 		spin_lock_irq(&wqe->lock);
 		if (io_wqe_run_queue(wqe)) {
 			__set_current_state(TASK_RUNNING);
@@ -526,8 +523,6 @@ static int io_wqe_worker(void *data)
 			break;
 	}
 
-	finish_wait(&worker->wait, &wait);
-
 	if (test_bit(IO_WQ_BIT_EXIT, &wq->state)) {
 		spin_lock_irq(&wqe->lock);
 		if (!wq_list_empty(&wqe->work_list))
@@ -589,7 +584,6 @@ static bool create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index)
 
 	refcount_set(&worker->ref, 1);
 	worker->nulls_node.pprev = NULL;
-	init_waitqueue_head(&worker->wait);
 	worker->wqe = wqe;
 	spin_lock_init(&worker->lock);