[PATCH liburing] Test wait after under-consuming

[Pavel Begunkov <asml.silence@gmail.com>]

In case of an error submission won't consume all sqes. This tests that
it will get back to the userspace even if (to_submit == to_wait)

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 test/link.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 55 insertions(+), 1 deletion(-)

diff --git a/test/link.c b/test/link.c
index 8ec1649..93653f3 100644
--- a/test/link.c
+++ b/test/link.c
@@ -384,6 +384,55 @@ err:
 	return 1;
 }
 
+static int test_early_fail_and_wait(struct io_uring *ring)
+{
+	struct io_uring_cqe *cqe;
+	struct io_uring_sqe *sqe;
+	int ret, submitted, i;
+	const int invalid_fd = 42;
+	struct iovec iov = { .iov_base = NULL, .iov_len = 0 };
+
+	sqe = io_uring_get_sqe(ring);
+	if (!sqe) {
+		printf("get sqe failed\n");
+		goto err;
+	}
+
+	io_uring_prep_readv(sqe, invalid_fd, &iov, 1, 0);
+	sqe->user_data = 1;
+	sqe->flags |= IOSQE_IO_LINK;
+
+	sqe = io_uring_get_sqe(ring);
+	if (!sqe) {
+		printf("get sqe failed\n");
+		goto err;
+	}
+
+	io_uring_prep_nop(sqe);
+	sqe->user_data = 2;
+
+	submitted = io_uring_submit_and_wait(ring, 2);
+	if (submitted == -EAGAIN)
+		return 0;
+	if (submitted <= 0) {
+		printf("sqe submit failed: %d\n", submitted);
+		goto err;
+	}
+
+	for (i = 0; i < 2; i++) {
+		ret = io_uring_wait_cqe(ring, &cqe);
+		if (ret < 0) {
+			printf("wait completion %d\n", ret);
+			goto err;
+		}
+		io_uring_cqe_seen(ring, cqe);
+	}
+
+	return 0;
+err:
+	return 1;
+}
+
 int main(int argc, char *argv[])
 {
 	struct io_uring ring, poll_ring;
@@ -400,7 +449,6 @@ int main(int argc, char *argv[])
 	if (ret) {
 		printf("poll_ring setup failed\n");
 		return 1;
-
 	}
 
 	ret = test_single_link(&ring);
@@ -439,5 +487,11 @@ int main(int argc, char *argv[])
 		return ret;
 	}
 
+	ret = test_early_fail_and_wait(&ring);
+	if (ret) {
+		fprintf(stderr, "test_early_fail_and_wait\n");
+		return ret;
+	}
+
 	return 0;
 }
-- 
2.24.0