io_uring: deduplicate failing task_work_add

When io_req_task_work_add() fails, the request will be cancelled by
enqueueing via task_works of io-wq. Extract a function for that.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -2171,6 +2171,16 @@ static int io_req_task_work_add(struct io_kiocb *req)
 	return ret;
 }
 
+static void io_req_task_work_add_fallback(struct io_kiocb *req,
+					  void (*cb)(struct callback_head *))
+{
+	struct task_struct *tsk = io_wq_get_task(req->ctx->io_wq);
+
+	init_task_work(&req->task_work, cb);
+	task_work_add(tsk, &req->task_work, TWA_NONE);
+	wake_up_process(tsk);
+}
+
 static void __io_req_task_cancel(struct io_kiocb *req, int error)
 {
 	struct io_ring_ctx *ctx = req->ctx;
@@ -2225,14 +2235,8 @@ static void io_req_task_queue(struct io_kiocb *req)
 	percpu_ref_get(&req->ctx->refs);
 
 	ret = io_req_task_work_add(req);
-	if (unlikely(ret)) {
-		struct task_struct *tsk;
-
-		init_task_work(&req->task_work, io_req_task_cancel);
-		tsk = io_wq_get_task(req->ctx->io_wq);
-		task_work_add(tsk, &req->task_work, TWA_NONE);
-		wake_up_process(tsk);
-	}
+	if (unlikely(ret))
+		io_req_task_work_add_fallback(req, io_req_task_cancel);
 }
 
 static inline void io_queue_next(struct io_kiocb *req)
@@ -2350,13 +2354,8 @@ static void io_free_req_deferred(struct io_kiocb *req)
 
 	init_task_work(&req->task_work, io_put_req_deferred_cb);
 	ret = io_req_task_work_add(req);
-	if (unlikely(ret)) {
-		struct task_struct *tsk;
-
-		tsk = io_wq_get_task(req->ctx->io_wq);
-		task_work_add(tsk, &req->task_work, TWA_NONE);
-		wake_up_process(tsk);
-	}
+	if (unlikely(ret))
+		io_req_task_work_add_fallback(req, io_put_req_deferred_cb);
 }
 
 static inline void io_put_req_deferred(struct io_kiocb *req, int refs)
@@ -3425,15 +3424,8 @@ static int io_async_buf_func(struct wait_queue_entry *wait, unsigned mode,
 	/* submit ref gets dropped, acquire a new one */
 	refcount_inc(&req->refs);
 	ret = io_req_task_work_add(req);
-	if (unlikely(ret)) {
-		struct task_struct *tsk;
-
-		/* queue just for cancelation */
-		init_task_work(&req->task_work, io_req_task_cancel);
-		tsk = io_wq_get_task(req->ctx->io_wq);
-		task_work_add(tsk, &req->task_work, TWA_NONE);
-		wake_up_process(tsk);
-	}
+	if (unlikely(ret))
+		io_req_task_work_add_fallback(req, io_req_task_cancel);
 	return 1;
 }
 
@@ -5153,12 +5145,8 @@ static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll,
 	 */
 	ret = io_req_task_work_add(req);
 	if (unlikely(ret)) {
-		struct task_struct *tsk;
-
 		WRITE_ONCE(poll->canceled, true);
-		tsk = io_wq_get_task(req->ctx->io_wq);
-		task_work_add(tsk, &req->task_work, TWA_NONE);
-		wake_up_process(tsk);
+		io_req_task_work_add_fallback(req, func);
 	}
 	return 1;
 }