From b12ab15f4a39c856beb01428db092776227abaec Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Mon, 20 Nov 2023 15:44:45 -0700
Subject: [PATCH] test/fixed-buf-merge: add test case for off-by-one in fixed
 buffer imports

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 test/Makefile          |  1 +
 test/fixed-buf-merge.c | 95 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 96 insertions(+)
 create mode 100644 test/fixed-buf-merge.c

diff --git a/test/Makefile b/test/Makefile
index 94bdc250c..ade84c304 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -88,6 +88,7 @@ test_srcs := \
 	file-update.c \
 	file-verify.c \
 	fixed-buf-iter.c \
+	fixed-buf-merge.c \
 	fixed-link.c \
 	fixed-reuse.c \
 	fpos.c \
diff --git a/test/fixed-buf-merge.c b/test/fixed-buf-merge.c
new file mode 100644
index 000000000..2e407fe8d
--- /dev/null
+++ b/test/fixed-buf-merge.c
@@ -0,0 +1,95 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Test fixed buffer merging/skipping
+ *
+ * Taken from: https://github.com/axboe/liburing/issues/994
+ *
+ */
+#include <stdio.h>
+#include <string.h>
+#include <fcntl.h>
+#include <stdlib.h>
+
+#include "liburing.h"
+#include "helpers.h"
+
+int main(int argc, char *argv[])
+{
+	int ret, i, fd, initial_offset = 4096, num_requests = 3;
+	struct io_uring ring;
+	struct io_uring_sqe *sqe;
+	struct io_uring_cqe *cqe;
+	struct iovec iov;
+	char *buffer, *to_free;
+	unsigned head;
+	char filename[64];
+
+	ret = io_uring_queue_init(4, &ring, 0);
+	if (ret) {
+		fprintf(stderr, "queue_init: %d\n", ret);
+		return T_EXIT_FAIL;
+	}
+
+	sprintf(filename, ".fixed-buf-%d", getpid());
+	t_create_file(filename, 4 * 4096);
+
+	fd = open(filename, O_RDONLY | O_DIRECT, 0644);
+	if (fd < 0) {
+		perror("open");
+		goto err_unlink;
+	}
+
+	to_free = buffer = aligned_alloc(4096, 128 * 4096);
+	if (!buffer) {
+		perror("aligned_alloc");
+		goto err_unlink;
+	}
+
+	/* Register buffer */
+	iov.iov_base = buffer;
+	iov.iov_len = 128 * 4096;
+
+	ret = io_uring_register_buffers(&ring, &iov, 1);
+	if (ret) {
+		fprintf(stderr, "buf register: %d\n", ret);
+		goto err_unlink;
+	}
+
+	/* Prepare read requests */
+	buffer += initial_offset;
+	for (i = 0; i < num_requests; i++) {
+		sqe = io_uring_get_sqe(&ring);
+		io_uring_prep_read_fixed(sqe, fd, buffer, 4096, 4096 * i, 0);
+		buffer += 4096;
+	}
+
+	/* Submit requests and reap completions */
+	ret = io_uring_submit_and_wait(&ring, num_requests);
+	if (ret != num_requests) {
+		fprintf(stderr, "Submit and wait: %d\n", ret);
+		goto err_unlink;
+	}
+
+	i = 0;
+	io_uring_for_each_cqe(&ring, head, cqe) {
+		if (cqe->res != 4096) {
+			fprintf(stderr, "cqe: %d\n", cqe->res);
+			goto err_unlink;
+		}
+		i++;
+	}
+
+	if (i != num_requests) {
+		fprintf(stderr, "Got %d completions\n", i);
+		goto err_unlink;
+	}
+
+	io_uring_cq_advance(&ring, i);
+	io_uring_queue_exit(&ring);
+	close(fd);
+	free(to_free);
+	return T_EXIT_PASS;
+err_unlink:
+	unlink(filename);
+	return T_EXIT_FAIL;
+}