Re: [PATCH v3 2/7] kunit: kunit-test: Add test cases for extending log buffer

[Rae Moar]

On Wed, Aug 9, 2023 at 11:54 AM Richard Fitzgerald
<rf@xxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Add test cases for the dynamically-extending log buffer.
>
> kunit_log_init_frag_test() tests that kunit_init_log_frag() correctly
> initializes new struct kunit_log_frag.
>
> kunit_log_extend_test_1() logs a series of numbered lines then tests
> that the resulting log contains all the lines.
>
> kunit_log_extend_test_2() logs a large number of lines of varying length
> to create many fragments, then tests that all lines are present.
>
> kunit_log_newline_test() has a new test to append a line that is exactly
> the length of the available space in the current fragment and check that
> the resulting log has a trailing '\n'.
>
> Signed-off-by: Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx>

Hello!

These tests now pass for me. Thanks!

I do have a few comments below mostly regarding comments and a few
clarifying questions.

-Rae

> ---
>  lib/kunit/kunit-test.c | 182 +++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 174 insertions(+), 8 deletions(-)
>
> diff --git a/lib/kunit/kunit-test.c b/lib/kunit/kunit-test.c
> index a199f83bac67..c0ee33a8031e 100644
> --- a/lib/kunit/kunit-test.c
> +++ b/lib/kunit/kunit-test.c
> @@ -7,6 +7,7 @@
>   */
>  #include <kunit/test.h>
>  #include <kunit/test-bug.h>
> +#include <linux/prandom.h>
>
>  #include "try-catch-impl.h"
>
> @@ -530,10 +531,12 @@ static struct kunit_suite kunit_resource_test_suite = {
>         .test_cases = kunit_resource_test_cases,
>  };
>
> -static char *get_concatenated_log(struct kunit *test, const struct list_head *log)
> +static char *get_concatenated_log(struct kunit *test, const struct list_head *log,
> +                                 int *num_frags)
>  {
>         struct kunit_log_frag *frag;
>         size_t len = 0;
> +       int frag_count = 0;
>         char *p;
>
>         list_for_each_entry(frag, log, list)
> @@ -542,24 +545,42 @@ static char *get_concatenated_log(struct kunit *test, const struct list_head *lo
>         len++; /* for terminating '\0' */
>         p = kunit_kzalloc(test, len, GFP_KERNEL);
>
> -       list_for_each_entry(frag, log, list)
> +       list_for_each_entry(frag, log, list) {
>                 strlcat(p, frag->buf, len);
> +               ++frag_count;
> +       }
> +
> +       if (num_frags)
> +               *num_frags = frag_count;
>
>         return p;
>  }
>
> -static void kunit_log_test(struct kunit *test)
> +static void kunit_log_init_frag_test(struct kunit *test)
>  {
> -       struct kunit_suite suite;
>         struct kunit_log_frag *frag;
>
> -       suite.log = kunit_kzalloc(test, sizeof(*suite.log), GFP_KERNEL);
> -       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, suite.log);
> -       INIT_LIST_HEAD(suite.log);
>         frag = kunit_kmalloc(test, sizeof(*frag), GFP_KERNEL);
>         KUNIT_ASSERT_NOT_ERR_OR_NULL(test, frag);
> +       memset(frag, 0x5a, sizeof(*frag));
> +

Why is the fragment getting filled here with memset? Should this be
tested? Feel free to let me know, I'm just uncertain.

>         kunit_init_log_frag(frag);
>         KUNIT_EXPECT_EQ(test, frag->buf[0], '\0');
> +       KUNIT_EXPECT_TRUE(test, list_is_first(&frag->list, &frag->list));
> +       KUNIT_EXPECT_TRUE(test, list_is_last(&frag->list, &frag->list));
> +}
> +
> +static void kunit_log_test(struct kunit *test)
> +{
> +       struct kunit_suite suite;
> +       struct kunit_log_frag *frag;
> +
> +       suite.log = kunit_kzalloc(test, sizeof(*suite.log), GFP_KERNEL);
> +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, suite.log);
> +       INIT_LIST_HEAD(suite.log);
> +       frag = kunit_kzalloc(test, sizeof(*frag), GFP_KERNEL);
> +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, frag);
> +       kunit_init_log_frag(frag);
>         list_add_tail(&frag->list, suite.log);
>
>         kunit_log(KERN_INFO, test, "put this in log.");
> @@ -586,23 +607,168 @@ static void kunit_log_test(struct kunit *test)
>
>  static void kunit_log_newline_test(struct kunit *test)
>  {
> +       struct kunit_suite suite;
>         struct kunit_log_frag *frag;
> +       char *p;

Similar to last email, could we change p to be a more descriptive name
such as concat_log?

>
>         kunit_info(test, "Add newline\n");
>         if (test->log) {
>                 frag = list_first_entry(test->log, struct kunit_log_frag, list);
>                 KUNIT_ASSERT_NOT_NULL_MSG(test, strstr(frag->buf, "Add newline\n"),
>                         "Missing log line, full log:\n%s",
> -                       get_concatenated_log(test, test->log));
> +                       get_concatenated_log(test, test->log, NULL));
>                 KUNIT_EXPECT_NULL(test, strstr(frag->buf, "Add newline\n\n"));
> +

Should this section of kunit_log_newline_test be separated into a new
test? This test seems a bit long and seems to have two distinct
sections?

> +               suite.log = kunit_kzalloc(test, sizeof(*suite.log), GFP_KERNEL);
> +               KUNIT_ASSERT_NOT_ERR_OR_NULL(test, suite.log);
> +               INIT_LIST_HEAD(suite.log);

I would love to see a comment here to explain and break up this
section similar to the comment from the previous email.

> +               frag = kunit_kzalloc(test, sizeof(*frag), GFP_KERNEL);
> +               KUNIT_ASSERT_NOT_ERR_OR_NULL(test, frag);
> +               kunit_init_log_frag(frag);
> +               list_add_tail(&frag->list, suite.log);
> +
> +               /* String that exactly fills fragment leaving no room for \n */
> +               memset(frag->buf, 0, sizeof(frag->buf));
> +               memset(frag->buf, 'x', sizeof(frag->buf) - 9);
> +               kunit_log_append(suite.log, "12345678");
> +               p = get_concatenated_log(test, suite.log, NULL);
> +               KUNIT_ASSERT_NOT_ERR_OR_NULL(test, p);
> +               KUNIT_EXPECT_NOT_NULL_MSG(test, strstr(p, "x12345678\n"),
> +                       "Newline not appended when fragment is full. Log is:\n'%s'", p);
>         } else {
>                 kunit_skip(test, "only useful when debugfs is enabled");
>         }
>  }
>
> +static void kunit_log_extend_test_1(struct kunit *test)

In general, I would really like to see more comments in the next two
tests describing the test behavior. I would prefer a comment for each
of the while/do-while loops below. I just found the behavior to be
slightly confusing to understand without comments (although I do
appreciate the comments that are in kunit_log_extend_test_2).

Also, I really appreciate how detailed these tests are.

Another potential idea is to rename these two tests to be
kunit_log_extend_test() and kunit_log_rand_extend_test() instead to be
more descriptive?

> +{
> +#ifdef CONFIG_KUNIT_DEBUGFS
> +       struct kunit_suite suite;
> +       struct kunit_log_frag *frag;
> +       char line[60];
> +       char *p, *pn;

Similar to before, could we change p and pn to be slightly more
descriptive names? Maybe concat_log and newline_ptr or newline_log or
newline_char?

> +       size_t len, n;
> +       int num_lines, num_frags, i;
> +
> +       suite.log = kunit_kzalloc(test, sizeof(*suite.log), GFP_KERNEL);
> +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, suite.log);
> +       INIT_LIST_HEAD(suite.log);
> +       frag = kunit_kzalloc(test, sizeof(*frag), GFP_KERNEL);
> +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, frag);
> +       kunit_init_log_frag(frag);
> +       list_add_tail(&frag->list, suite.log);
> +
> +       i = 0;
> +       len = 0;
> +       do {
> +               n = snprintf(line, sizeof(line),
> +                            "The quick brown fox jumps over the lazy penguin %d\n", i);
> +               KUNIT_ASSERT_LT(test, n, sizeof(line));
> +               kunit_log_append(suite.log, line);
> +               ++i;
> +               len += n;
> +       }  while (len < (sizeof(frag->buf) * 30));

Are we trying to restrict the num_frags to less than 30? And then we
could check that with a KUNIT_EXPECT? Currently, the num_frags are
just above 30. That is ok too. I just was wondering if this was
intentional? (Same as kunit_log_extend_test_2)

> +       num_lines = i;
> +
> +       p = get_concatenated_log(test, suite.log, &num_frags);
> +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, p);
> +       KUNIT_EXPECT_GT(test, num_frags, 1);
> +
> +       kunit_info(test, "num lines:%d num_frags:%d total len:%zu\n",
> +                  num_lines, num_frags, strlen(p));
> +
> +       i = 0;
> +       while ((pn = strchr(p, '\n')) != NULL) {
> +               *pn = '\0';
> +               snprintf(line, sizeof(line),
> +                        "The quick brown fox jumps over the lazy penguin %d", i);
> +               KUNIT_EXPECT_STREQ(test, p, line);
> +               p = pn + 1;
> +               ++i;
> +       }
> +       KUNIT_EXPECT_EQ(test, i, num_lines);
> +#else
> +       kunit_skip(test, "only useful when debugfs is enabled");
> +#endif
> +}
> +
> +static void kunit_log_extend_test_2(struct kunit *test)
> +{
> +#ifdef CONFIG_KUNIT_DEBUGFS
> +       struct kunit_suite suite;
> +       struct kunit_log_frag *frag;
> +       struct rnd_state rnd;
> +       char line[101];
> +       char *p, *pn;

Similar to above, could p and pn be renamed to be more descriptive?

> +       size_t len;
> +       int num_lines, num_frags, n, i;
> +
> +       suite.log = kunit_kzalloc(test, sizeof(*suite.log), GFP_KERNEL);
> +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, suite.log);
> +       INIT_LIST_HEAD(suite.log);
> +       frag = kunit_kzalloc(test, sizeof(*frag), GFP_KERNEL);
> +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, frag);
> +       kunit_init_log_frag(frag);
> +       list_add_tail(&frag->list, suite.log);
> +
> +       /* Build log line of varying content */
> +       line[0] = '\0';
> +       i = 0;
> +       do {
> +               char tmp[9];
> +
> +               snprintf(tmp, sizeof(tmp), "%x", i++);
> +               len = strlcat(line, tmp, sizeof(line));
> +       } while (len < sizeof(line) - 1);

Could there be an expectation statement here to check the line has
been properly filled. Maybe checking the length?

> +
> +       /*
> +        * Log lines of different lengths until we have created
> +        * many fragments.
> +        * The "randomness" must be repeatable.
> +        */
> +       prandom_seed_state(&rnd, 3141592653589793238ULL);
> +       i = 0;
> +       len = 0;
> +       num_lines = 0;
> +       do {
> +               kunit_log_append(suite.log, "%s\n", &line[i]);
> +               len += sizeof(line) - i;
> +               num_lines++;
> +               i = prandom_u32_state(&rnd) % (sizeof(line) - 1);
> +       } while (len < (sizeof(frag->buf) * 30));
> +
> +       /* There must be more than one buffer fragment now */
> +       KUNIT_EXPECT_FALSE(test, list_is_singular(suite.log));
> +
> +       p = get_concatenated_log(test, suite.log, &num_frags);
> +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, p);
> +       KUNIT_EXPECT_GT(test, num_frags, 1);
> +
> +       kunit_info(test, "num lines:%d num_frags:%d total len:%zu\n",
> +                  num_lines, num_frags, strlen(p));
> +
> +       prandom_seed_state(&rnd, 3141592653589793238ULL);
> +       i = 0;
> +       n = 0;
> +       while ((pn = strchr(p, '\n')) != NULL) {
> +               *pn = '\0';
> +               KUNIT_EXPECT_STREQ(test, p, &line[i]);
> +               p = pn + 1;
> +               n++;
> +               i = prandom_u32_state(&rnd) % (sizeof(line) - 1);
> +       }
> +       KUNIT_EXPECT_EQ_MSG(test, n, num_lines, "Not enough lines.");

Is it possible for this to be too many lines instead? Should this
comment instead be "Unexpected number of lines". Also could we have a
similar message for the test above for this expectation regarding the
number of lines.


> +#else
> +       kunit_skip(test, "only useful when debugfs is enabled");
> +#endif
> +}
> +
>  static struct kunit_case kunit_log_test_cases[] = {
> +       KUNIT_CASE(kunit_log_init_frag_test),
>         KUNIT_CASE(kunit_log_test),
>         KUNIT_CASE(kunit_log_newline_test),
> +       KUNIT_CASE(kunit_log_extend_test_1),
> +       KUNIT_CASE(kunit_log_extend_test_2),
>         {}
>  };
>
> --
> 2.30.2
>