add test case for 5.4 io merge regression logic

Prior to switching io-wq we try to merge adjacent read/write requests.
But because of bug in merge logic io may stuck

2 files changed, 97 insertions, 0 deletions

diff --git a/test/Makefile b/test/Makefile
index 2751f67..be34856 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -86,6 +86,7 @@ test_targets += \
 	rename \
 	ring-leak \
 	ring-leak2 \
+	rw_merge_test \
 	self \
 	send_recv \
 	send_recvmsg \
@@ -219,6 +220,7 @@ test_srcs := \
 	rename.c \
 	ring-leak.c \
 	ring-leak2.c \
+	rw_merge_test.c \
 	self.c \
 	send_recvmsg.c \
 	shared-wq.c \
diff --git a/test/rw_merge_test.c b/test/rw_merge_test.c
new file mode 100644
index 0000000..2c60293
--- /dev/null
+++ b/test/rw_merge_test.c
@@ -0,0 +1,95 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Regression test for incorrect async_list io_should_merge() logic
+ * Bug was fixed in 5.5 by (commit: 561fb04 io_uring: replace workqueue usage with io-wq")
+ * Affects 5.4 lts branch, at least 5.4.106 is affected.
+ */
+#include <stdio.h>
+#include <errno.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <assert.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "liburing.h"
+
+int main(int argc, char *argv[])
+{
+	struct io_uring_sqe *sqe;
+	struct io_uring_cqe *cqe;
+	struct io_uring ring;
+	int ret, fd, pipe1[2];
+	char buf[4096];
+	struct iovec vec = {
+		.iov_base = buf,
+		.iov_len = sizeof(buf)
+	};
+	struct __kernel_timespec ts = {.tv_sec = 3, .tv_nsec = 0};
+
+	ret = pipe(pipe1);
+	assert(!ret);
+
+	fd = open("testfile", O_RDWR | O_CREAT, 0644);
+	assert(ret>=0);
+	ret = ftruncate(fd, 4096);
+	assert(!ret);
+
+	ret = io_uring_queue_init(4, &ring, 0);
+	if (ret) {
+		printf("io_uring_queue_init fail,"
+		       " please CONFIG_IO_URING kernel config option");
+		return 1;
+	}
+
+	/* REQ1 */
+	sqe = io_uring_get_sqe(&ring);
+	io_uring_prep_readv(sqe, pipe1[0], &vec, 1, 0);
+	sqe->user_data = 1;
+
+	/* REQ2 */
+	sqe = io_uring_get_sqe(&ring);
+	io_uring_prep_readv(sqe, fd, &vec, 1, 4096);
+	sqe->user_data = 2;
+
+	ret = io_uring_submit(&ring);
+	assert(ret == 2);
+
+	ret = io_uring_wait_cqe(&ring, &cqe);
+	assert(!ret);
+	assert(cqe->res == 0);
+	assert(cqe->user_data == 2);
+	io_uring_cqe_seen(&ring, cqe);
+
+	/*
+	 * REQ3
+	 * Prepare request adjacent to previous one, so merge logic may want to
+	 * link it to previous request, but because of a bug in merge logic
+	 * it may be merged with <REQ1> request
+	 */
+	sqe = io_uring_get_sqe(&ring);
+	io_uring_prep_readv(sqe, fd, &vec, 1, 2048);
+	sqe->user_data = 3;
+
+	ret = io_uring_submit(&ring);
+	assert(ret == 1);
+
+	/*
+	 * Read may stuck because of bug there request was be incorrecly
+	 * merged with <REQ1> request
+	 */
+	ret = io_uring_wait_cqe_timeout(&ring, &cqe, &ts);
+	if (ret == -ETIME) {
+		printf("TEST_FAIL: readv req3 stuck\n");
+		return 1;
+	}
+	assert(!ret);
+
+	assert(cqe->res == 2048);
+	assert(cqe->user_data == 3);
+
+	io_uring_cqe_seen(&ring, cqe);
+	io_uring_queue_exit(&ring);
+
+	return 0;
+}