io_uring: check for need to re-wait in polled async handling

We added this for just the regular poll requests in commit a6ba632d
("io_uring: retry poll if we got woken with non-matching mask"), we
should do the same for the poll handler used pollable async requests.
Move the re-wait check and arm into a helper, and call it from
io_async_task_func() as well.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -4156,6 +4156,26 @@ static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll,
 	return 1;
 }
 
+static bool io_poll_rewait(struct io_kiocb *req, struct io_poll_iocb *poll)
+	__acquires(&req->ctx->completion_lock)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+
+	if (!req->result && !READ_ONCE(poll->canceled)) {
+		struct poll_table_struct pt = { ._key = poll->events };
+
+		req->result = vfs_poll(req->file, &pt) & poll->events;
+	}
+
+	spin_lock_irq(&ctx->completion_lock);
+	if (!req->result && !READ_ONCE(poll->canceled)) {
+		add_wait_queue(poll->head, &poll->wait);
+		return true;
+	}
+
+	return false;
+}
+
 static void io_async_task_func(struct callback_head *cb)
 {
 	struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work);
@@ -4164,13 +4184,15 @@ static void io_async_task_func(struct callback_head *cb)
 
 	trace_io_uring_task_run(req->ctx, req->opcode, req->user_data);
 
-	WARN_ON_ONCE(!list_empty(&req->apoll->poll.wait.entry));
+	if (io_poll_rewait(req, &apoll->poll)) {
+		spin_unlock_irq(&ctx->completion_lock);
+		return;
+	}
 
-	if (hash_hashed(&req->hash_node)) {
-		spin_lock_irq(&ctx->completion_lock);
+	if (hash_hashed(&req->hash_node))
 		hash_del(&req->hash_node);
+
 	spin_unlock_irq(&ctx->completion_lock);
-	}
 
 	/* restore ->work in case we need to retry again */
 	memcpy(&req->work, &apoll->work, sizeof(req->work));
@@ -4436,18 +4458,11 @@ static void io_poll_task_handler(struct io_kiocb *req, struct io_kiocb **nxt)
 	struct io_ring_ctx *ctx = req->ctx;
 	struct io_poll_iocb *poll = &req->poll;
 
-	if (!req->result && !READ_ONCE(poll->canceled)) {
-		struct poll_table_struct pt = { ._key = poll->events };
-
-		req->result = vfs_poll(req->file, &pt) & poll->events;
-	}
-
-	spin_lock_irq(&ctx->completion_lock);
-	if (!req->result && !READ_ONCE(poll->canceled)) {
-		add_wait_queue(poll->head, &poll->wait);
+	if (io_poll_rewait(req, poll)) {
 		spin_unlock_irq(&ctx->completion_lock);
 		return;
 	}
+
 	hash_del(&req->hash_node);
 	io_poll_complete(req, req->result, 0);
 	req->flags |= REQ_F_COMP_LOCKED;