io_uring: get rid of kiocb_wait_page_queue_init()

The 5.9 merge moved this function io_uring, which means that we don't
need to retain the generic nature of it. Clean up this part by removing
redundant checks, and just inlining the small remainder in
io_rw_should_retry().

No functional changes in this patch.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -3074,27 +3074,6 @@ static int io_async_buf_func(struct wait_queue_entry *wait, unsigned mode,
 	return 1;
 }
 
-static inline int kiocb_wait_page_queue_init(struct kiocb *kiocb,
-					     struct wait_page_queue *wait,
-					     wait_queue_func_t func,
-					     void *data)
-{
-	/* Can't support async wakeup with polled IO */
-	if (kiocb->ki_flags & IOCB_HIPRI)
-		return -EINVAL;
-	if (kiocb->ki_filp->f_mode & FMODE_BUF_RASYNC) {
-		wait->wait.func = func;
-		wait->wait.private = data;
-		wait->wait.flags = 0;
-		INIT_LIST_HEAD(&wait->wait.entry);
-		kiocb->ki_flags |= IOCB_WAITQ;
-		kiocb->ki_waitq = wait;
-		return 0;
-	}
-
-	return -EOPNOTSUPP;
-}
-
 /*
  * This controls whether a given IO request should be armed for async page
  * based retry. If we return false here, the request is handed to the async
@@ -3109,16 +3088,17 @@ static inline int kiocb_wait_page_queue_init(struct kiocb *kiocb,
  */
 static bool io_rw_should_retry(struct io_kiocb *req)
 {
+	struct wait_page_queue *wait = &req->io->rw.wpq;
 	struct kiocb *kiocb = &req->rw.kiocb;
-	int ret;
 
 	/* never retry for NOWAIT, we just complete with -EAGAIN */
 	if (req->flags & REQ_F_NOWAIT)
 		return false;
 
 	/* Only for buffered IO */
-	if (kiocb->ki_flags & IOCB_DIRECT)
+	if (kiocb->ki_flags & (IOCB_DIRECT | IOCB_HIPRI))
 		return false;
+
 	/*
 	 * just use poll if we can, and don't attempt if the fs doesn't
 	 * support callback based unlocks
@@ -3126,14 +3106,15 @@ static bool io_rw_should_retry(struct io_kiocb *req)
 	if (file_can_poll(req->file) || !(req->file->f_mode & FMODE_BUF_RASYNC))
 		return false;
 
-	ret = kiocb_wait_page_queue_init(kiocb, &req->io->rw.wpq,
-						io_async_buf_func, req);
-	if (!ret) {
+	wait->wait.func = io_async_buf_func;
+	wait->wait.private = req;
+	wait->wait.flags = 0;
+	INIT_LIST_HEAD(&wait->wait.entry);
+	kiocb->ki_flags |= IOCB_WAITQ;
+	kiocb->ki_waitq = wait;
+
 	io_get_req_task(req);
 	return true;
-	}
-
-	return false;
 }
 
 static int io_iter_do_read(struct io_kiocb *req, struct iov_iter *iter)