io_uring/waitid: setup async data in the prep handler

This is the idiomatic way that opcodes should setup their async data,
so that it's always valid inside ->issue() without issue needing to
do that.

Fixes: f31ecf6 ("io_uring: add IORING_OP_WAITID support")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: axboe

io_uring/waitid.c

@@ -285,10 +285,16 @@ static int io_waitid_wait(struct wait_queue_entry *wait, unsigned mode,
 int io_waitid_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
+	struct io_waitid_async *iwa;
 
 	if (sqe->addr || sqe->buf_index || sqe->addr3 || sqe->waitid_flags)
 		return -EINVAL;
 
+	iwa = io_uring_alloc_async_data(NULL, req);
+	if (!unlikely(iwa))
+		return -ENOMEM;
+	iwa->req = req;
+
 	iw->which = READ_ONCE(sqe->len);
 	iw->upid = READ_ONCE(sqe->fd);
 	iw->options = READ_ONCE(sqe->file_index);
@@ -299,16 +305,10 @@ int io_waitid_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 int io_waitid(struct io_kiocb *req, unsigned int issue_flags)
 {
 	struct io_waitid *iw = io_kiocb_to_cmd(req, struct io_waitid);
+	struct io_waitid_async *iwa = req->async_data;
 	struct io_ring_ctx *ctx = req->ctx;
-	struct io_waitid_async *iwa;
 	int ret;
 
-	iwa = io_uring_alloc_async_data(NULL, req);
-	if (!iwa)
-		return -ENOMEM;
-
-	iwa->req = req;
-
 	ret = kernel_waitid_prepare(&iwa->wo, iw->which, iw->upid, &iw->info,
 					iw->options, NULL);
 	if (ret)