[PATCH liburing] test/read-write: add test for CQE res when removing buffers

[Wojciech Lukowicz <wlukowicz01@gmail.com>]

When removing provided buffers, CQE res should contain the number of
removed buffers. However, in certain kernel versions, if SQE requests
removal of more buffers than available, then res will contain the number
of removed buffers + 1.

Signed-off-by: Wojciech Lukowicz <wlukowicz01@gmail.com>
---
This is a failing test, needs the patch I sent earlier.

 test/read-write.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/test/read-write.c b/test/read-write.c
index 3764f6aef47e..6f24ec919de3 100644
--- a/test/read-write.c
+++ b/test/read-write.c
@@ -637,6 +637,53 @@ static int test_rem_buf(int batch, int sqe_flags)
 	return ret;
 }
 
+static int test_rem_buf_single(int to_rem)
+{
+	struct io_uring_sqe *sqe;
+	struct io_uring_cqe *cqe;
+	struct io_uring ring;
+	int ret, expected;
+	int bgid = 1;
+
+	if (no_buf_select)
+		return 0;
+
+	ret = io_uring_queue_init(64, &ring, 0);
+	if (ret) {
+		fprintf(stderr, "ring create failed: %d\n", ret);
+		return 1;
+	}
+
+	ret = provide_buffers_iovec(&ring, bgid);
+	if (ret)
+		return ret;
+
+	expected = (to_rem > BUFFERS) ? BUFFERS : to_rem;
+
+	sqe = io_uring_get_sqe(&ring);
+	io_uring_prep_remove_buffers(sqe, to_rem, bgid);
+
+	ret = io_uring_submit(&ring);
+	if (ret != 1) {
+		fprintf(stderr, "submit: %d\n", ret);
+		return -1;
+	}
+
+	ret = io_uring_wait_cqe(&ring, &cqe);
+	if (ret) {
+		fprintf(stderr, "wait_cqe=%d\n", ret);
+		return 1;
+	}
+	if (cqe->res != expected) {
+		fprintf(stderr, "cqe->res=%d, expected=%d\n", cqe->res, expected);
+		return 1;
+	}
+	io_uring_cqe_seen(&ring, cqe);
+
+	io_uring_queue_exit(&ring);
+	return ret;
+}
+
 static int test_io_link(const char *file)
 {
 	const int nr_links = 100;
@@ -950,6 +997,12 @@ int main(int argc, char *argv[])
 		}
 	}
 
+	ret = test_rem_buf_single(BUFFERS + 1);
+	if (ret) {
+		fprintf(stderr, "test_rem_buf_single(BUFFERS + 1) failed\n");
+		goto err;
+	}
+
 	if (fname != argv[1])
 		unlink(fname);
 	return 0;
-- 
2.30.2