[PATCH v2 1/7] kunit: Add parent kunit for parameterized test context

[Marie Zhussupova <marievic@google.com>]

Currently, KUnit parameterized tests lack a mechanism
to share resources across parameter runs because the
same `struct kunit` instance is cleaned up and
reused for each run.

This patch introduces parameterized test context,
enabling test users to share resources between
parameter runs. It also allows setting up resources
that need to be available for all parameter runs only once,
which is helpful in cases where setup is expensive.

To establish a parameterized test context, this
patch adds a parent pointer field to `struct kunit`.
This allows resources added to the parent `struct kunit`
to be shared and accessible across all parameter runs.

In kunit_run_tests(), the default `struct kunit`
created is now designated to act as the parameterized
test context whenever a test is parameterized.

Subsequently, a new `struct kunit` is made
for each parameter run, and its parent pointer is
set to the `struct kunit` that holds the
parameterized test context.

Signed-off-by: Marie Zhussupova <marievic@google.com>
---

Changes in v2:

- Descriptions of the parent pointer in `struct kunit`
  were changed to be more general, as it could be
  used to share resources not only between parameter
  runs but also between test cases in the future.
- When printing parameter descriptions using
  test.param_index was changed to param_test.param_index.
- kunit_cleanup(&test) in kunit_run_tests() was moved
  inside the parameterized test check.
- The comments and the commit message were changed to
  reflect the parameterized testing terminology. See
  the patch series cover letter change log for the
  definitions.

---
 include/kunit/test.h |  8 ++++++--
 lib/kunit/test.c     | 34 ++++++++++++++++++++--------------
 2 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/include/kunit/test.h b/include/kunit/test.h
index 39c768f87dc9..b47b9a3102f3 100644
--- a/include/kunit/test.h
+++ b/include/kunit/test.h
@@ -268,14 +268,18 @@ struct kunit_suite_set {
  *
  * @priv: for user to store arbitrary data. Commonly used to pass data
  *	  created in the init function (see &struct kunit_suite).
+ * @parent: reference to the parent context of type struct kunit that can
+ *	    be used for storing shared resources.
  *
  * Used to store information about the current context under which the test
  * is running. Most of this data is private and should only be accessed
- * indirectly via public functions; the one exception is @priv which can be
- * used by the test writer to store arbitrary data.
+ * indirectly via public functions; the two exceptions are @priv and @parent
+ * which can be used by the test writer to store arbitrary data and access the
+ * parent context, respectively.
  */
 struct kunit {
 	void *priv;
+	struct kunit *parent;
 
 	/* private: internal use only. */
 	const char *name; /* Read only after initialization! */
diff --git a/lib/kunit/test.c b/lib/kunit/test.c
index f3c6b11f12b8..14a8bd846939 100644
--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -647,6 +647,7 @@ int kunit_run_tests(struct kunit_suite *suite)
 	struct kunit_case *test_case;
 	struct kunit_result_stats suite_stats = { 0 };
 	struct kunit_result_stats total_stats = { 0 };
+	const void *curr_param;
 
 	/* Taint the kernel so we know we've run tests. */
 	add_taint(TAINT_TEST, LOCKDEP_STILL_OK);
@@ -679,37 +680,42 @@ int kunit_run_tests(struct kunit_suite *suite)
 		} else {
 			/* Get initial param. */
 			param_desc[0] = '\0';
-			test.param_value = test_case->generate_params(NULL, param_desc);
+			/* TODO: Make generate_params try-catch */
+			curr_param = test_case->generate_params(NULL, param_desc);
 			test_case->status = KUNIT_SKIPPED;
 			kunit_log(KERN_INFO, &test, KUNIT_SUBTEST_INDENT KUNIT_SUBTEST_INDENT
 				  "KTAP version 1\n");
 			kunit_log(KERN_INFO, &test, KUNIT_SUBTEST_INDENT KUNIT_SUBTEST_INDENT
 				  "# Subtest: %s", test_case->name);
 
-			while (test.param_value) {
-				kunit_run_case_catch_errors(suite, test_case, &test);
+			while (curr_param) {
+				struct kunit param_test = {
+					.param_value = curr_param,
+					.param_index = ++test.param_index,
+					.parent = &test,
+				};
+				kunit_init_test(&param_test, test_case->name, test_case->log);
+				kunit_run_case_catch_errors(suite, test_case, &param_test);
 
 				if (param_desc[0] == '\0') {
 					snprintf(param_desc, sizeof(param_desc),
-						 "param-%d", test.param_index);
+						 "param-%d", param_test.param_index);
 				}
 
-				kunit_print_ok_not_ok(&test, KUNIT_LEVEL_CASE_PARAM,
-						      test.status,
-						      test.param_index + 1,
+				kunit_print_ok_not_ok(&param_test, KUNIT_LEVEL_CASE_PARAM,
+						      param_test.status,
+						      param_test.param_index,
 						      param_desc,
-						      test.status_comment);
+						      param_test.status_comment);
 
-				kunit_update_stats(&param_stats, test.status);
+				kunit_update_stats(&param_stats, param_test.status);
 
 				/* Get next param. */
 				param_desc[0] = '\0';
-				test.param_value = test_case->generate_params(test.param_value, param_desc);
-				test.param_index++;
-				test.status = KUNIT_SUCCESS;
-				test.status_comment[0] = '\0';
-				test.priv = NULL;
+				curr_param = test_case->generate_params(curr_param, param_desc);
 			}
+			/* TODO: Put this kunit_cleanup into a try-catch. */
+			kunit_cleanup(&test);
 		}
 
 		kunit_print_attr((void *)test_case, true, KUNIT_LEVEL_CASE);
-- 
2.51.0.rc0.205.g4a044479a3-goog