io-wq: remove unused io-wq refcounting

iowq->refs is initialised to one and killed on exit, so it's not used
and we can kill it.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/401007393528ea7c102360e69a29b64498e15db2.1623634181.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

fs/io-wq.c

@@ -109,8 +109,6 @@ struct io_wq {
 
 	struct io_wq_hash *hash;
 
-	refcount_t refs;
-
 	atomic_t worker_refs;
 	struct completion worker_done;
 
@@ -949,7 +947,6 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
 	}
 
 	wq->task = get_task_struct(data->task);
-	refcount_set(&wq->refs, 1);
 	atomic_set(&wq->worker_refs, 1);
 	init_completion(&wq->worker_done);
 	return wq;
@@ -1038,7 +1035,6 @@ void io_wq_put_and_exit(struct io_wq *wq)
 	WARN_ON_ONCE(!test_bit(IO_WQ_BIT_EXIT, &wq->state));
 
 	io_wq_exit_workers(wq);
-	if (refcount_dec_and_test(&wq->refs))
 	io_wq_destroy(wq);
 }