[PATCH v4 08/10] smb/client: introduce smb2maperror KUnit tests

[chenxiaosong.chenxiaosong@linux.dev]

From: ChenXiaoSong <chenxiaosong@kylinos.cn>

The KUnit tests are executed when cifs.ko is loaded.

Just like fs/ext4/mballoc.c includes fs/ext4/mballoc-test.c.
smb2maperror.c also includes smb2maperror_test.c, allowing KUnit tests to
access any functions and variables in smb2maperror.c.

The maperror_test_check_sort() checks whether the array is properly sorted.

The maperror_test_check_search() checks whether the expected element can be
correctly searched for in the smb2_error_map_table array.

Signed-off-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
---
 fs/smb/Kconfig                    | 17 ++++++++
 fs/smb/client/smb2maperror.c      |  4 ++
 fs/smb/client/smb2maperror_test.c | 71 +++++++++++++++++++++++++++++++
 3 files changed, 92 insertions(+)
 create mode 100644 fs/smb/client/smb2maperror_test.c

diff --git a/fs/smb/Kconfig b/fs/smb/Kconfig
index ef425789fa6a..85f7ad5fbc5e 100644
--- a/fs/smb/Kconfig
+++ b/fs/smb/Kconfig
@@ -9,3 +9,20 @@ config SMBFS
 	tristate
 	default y if CIFS=y || SMB_SERVER=y
 	default m if CIFS=m || SMB_SERVER=m
+
+config SMB_KUNIT_TESTS
+	tristate "KUnit tests for SMB" if !KUNIT_ALL_TESTS
+	depends on SMBFS && KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  This builds the SMB KUnit tests.
+
+	  KUnit tests run during boot and output the results to the debug log
+	  in TAP format (https://testanything.org/). Only useful for kernel devs
+	  running KUnit test harness and are not for inclusion into a production
+	  build.
+
+	  For more information on KUnit and unit tests in general please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+	  If unsure, say N.
diff --git a/fs/smb/client/smb2maperror.c b/fs/smb/client/smb2maperror.c
index 0d46fa98952c..dc2edeafc93b 100644
--- a/fs/smb/client/smb2maperror.c
+++ b/fs/smb/client/smb2maperror.c
@@ -2490,3 +2490,7 @@ void smb2_init_maperror(void)
 	     sizeof(struct status_to_posix_error),
 	     cmp_smb2_status, NULL);
 }
+
+#if IS_ENABLED(CONFIG_SMB_KUNIT_TESTS)
+#include "smb2maperror_test.c"
+#endif /* CONFIG_SMB_KUNIT_TESTS */
diff --git a/fs/smb/client/smb2maperror_test.c b/fs/smb/client/smb2maperror_test.c
new file mode 100644
index 000000000000..b807a860ca59
--- /dev/null
+++ b/fs/smb/client/smb2maperror_test.c
@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: LGPL-2.1
+/*
+ *
+ *   KUnit tests of SMB2 maperror
+ *
+ *   Copyright (C) 2025 KylinSoft Co., Ltd. All rights reserved.
+ *   Author(s): ChenXiaoSong <chenxiaosong@kylinos.cn>
+ *
+ */
+
+#include <kunit/test.h>
+
+static void maperror_test_check_sort(struct kunit *test)
+{
+	bool is_sorted = true;
+	unsigned int i;
+
+	for (i = 1; i < err_map_num; i++) {
+		if (smb2_error_map_table[i].smb2_status >=
+		    smb2_error_map_table[i - 1].smb2_status)
+			continue;
+
+		pr_err("smb2_error_map_table array order is incorrect\n");
+		is_sorted = false;
+		break;
+	}
+
+	KUNIT_EXPECT_EQ(test, true, is_sorted);
+}
+
+static void
+test_cmp_map(struct kunit *test, struct status_to_posix_error *expect)
+{
+	struct status_to_posix_error *result;
+
+	result = smb2_get_err_map(expect->smb2_status);
+	KUNIT_EXPECT_PTR_NE(test, NULL, result);
+	KUNIT_EXPECT_EQ(test, expect->smb2_status, result->smb2_status);
+	KUNIT_EXPECT_EQ(test, expect->posix_error, result->posix_error);
+	KUNIT_EXPECT_STREQ(test, expect->status_string, result->status_string);
+}
+
+static void maperror_test_check_search(struct kunit *test)
+{
+	unsigned int i;
+	struct status_to_posix_error expect;
+
+	for (i = 0; i < err_map_num; i++) {
+		expect = smb2_error_map_table[i];
+		test_cmp_map(test, &expect);
+	}
+}
+
+/*
+ * Before running these test cases, the smb2_init_maperror()
+ * function is called first.
+ */
+static struct kunit_case maperror_test_cases[] = {
+	KUNIT_CASE(maperror_test_check_sort),
+	KUNIT_CASE(maperror_test_check_search),
+	{}
+};
+
+static struct kunit_suite maperror_suite = {
+	.name = "smb2_maperror",
+	.test_cases = maperror_test_cases,
+};
+
+kunit_test_suite(maperror_suite);
+
+MODULE_LICENSE("GPL");
-- 
2.43.0