workqueue: Replace deprecated ida_simple_*() with ida_alloc()/ida_free()

Replace ida_simple_get() with ida_alloc() and ida_simple_remove() with
ida_free(), the latter is more concise and intuitive.

In addition, if ida_alloc() fails, NULL is returned directly. This
eliminates unnecessary initialization of two local variables and an 'if'
judgment.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

kernel/workqueue.c

@@ -1912,14 +1912,14 @@ static void worker_detach_from_pool(struct worker *worker)
  */
 static struct worker *create_worker(struct worker_pool *pool)
 {
-	struct worker *worker = NULL;
-	int id = -1;
+	struct worker *worker;
+	int id;
 	char id_buf[16];
 
 	/* ID is needed to determine kthread name */
-	id = ida_simple_get(&pool->worker_ida, 0, 0, GFP_KERNEL);
+	id = ida_alloc(&pool->worker_ida, GFP_KERNEL);
 	if (id < 0)
-		goto fail;
+		return NULL;
 
 	worker = alloc_worker(pool->node);
 	if (!worker)
@@ -1954,8 +1954,7 @@ static struct worker *create_worker(struct worker_pool *pool)
 	return worker;
 
 fail:
-	if (id >= 0)
-		ida_simple_remove(&pool->worker_ida, id);
+	ida_free(&pool->worker_ida, id);
 	kfree(worker);
 	return NULL;
 }
@@ -2378,7 +2377,7 @@ static int worker_thread(void *__worker)
 		set_pf_worker(false);
 
 		set_task_comm(worker->task, "kworker/dying");
-		ida_simple_remove(&pool->worker_ida, worker->id);
+		ida_free(&pool->worker_ida, worker->id);
 		worker_detach_from_pool(worker);
 		kfree(worker);
 		return 0;