Message-ID: <CABVgOSk85sNKxRF9CZfiTpBLJMzLn4LzmbJYb7sAaNSZaw4_WQ@mail.gmail.com>
Date:   Fri, 20 Jan 2023 14:06:53 +0800
From:   David Gow <davidgow@...gle.com>
To:     Rae Moar <rmoar@...gle.com>
Cc:     brendanhiggins@...gle.com, dlatypov@...gle.com,
        skhan@...uxfoundation.org, kunit-dev@...glegroups.com,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v2] lib/hashtable_test.c: add test for the hashtable structure

On Wed, 18 Jan 2023 at 05:50, Rae Moar <rmoar@...gle.com> wrote:
>
> Add a KUnit test for the kernel hashtable implementation in
> include/linux/hashtable.h.
>
> Note that this version does not yet test each of the rcu
> alternative versions of functions.
>
> Signed-off-by: Rae Moar <rmoar@...gle.com>
> ---

This looks good, and TBH, I could accept it as-is. There are a few
very minor stylistic nitpicks below, but there are a couple of bigger
issues, too:
- DEFINE_HASHTABLE() should initialise the hashtable itself, so you
shouldn't need to also call hash_init().
- It'd be nice if we had some hashtables of different sizes. At the
moment, they're all 3-bit (8 entries). Let's mix it up a little bit.

With those two changes (and optionally, any of the stylistic ones
below), this is:
Reviewed-by: David Gow <davidgow@...gle.com>

Cheers,
-- David

>
> Changes since v1:
> - Change Kconfig.debug message to be more succinct.
> - Directly increment current element's visited field rather than looking
>   up corresponding element.
> - Use KUNIT_EXPECT_… statements to check keys are within range rather
>   than using if statements.
> - Change hash_for_each_possible test to check buckets using a
>   hash_for_each method instead of calculating the bucket number using
>   hash_min.
>
> Note: The check patch script is outputting open brace errors on lines
> 158, 192, 247 of lib/hashtable_test.c. However, I think these errors are
> a mistake as the format of the braces on those lines seems consistent
> with the Linux Kernel style guide.
>

This is a known issue with checkpatch and function names with
"for_each" in them. It was discussed here, and we ultimately decided
just to ignore the warnings:
https://lore.kernel.org/all/CABVgOSmCHbGjZBjeWSbPEZbJw22SaBQnoO77xxNzN_ugAwzNiQ@mail.gmail.com/

>  lib/Kconfig.debug    |  13 ++
>  lib/Makefile         |   1 +
>  lib/hashtable_test.c | 326 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 340 insertions(+)
>  create mode 100644 lib/hashtable_test.c
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 881c3f84e88a..69b1452a3eeb 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -2496,6 +2496,19 @@ config LIST_KUNIT_TEST
>
>           If unsure, say N.
>
> +config HASHTABLE_KUNIT_TEST
> +       tristate "KUnit Test for Kernel Hashtable structures" if !KUNIT_ALL_TESTS
> +       depends on KUNIT
> +       default KUNIT_ALL_TESTS
> +       help
> +         This builds the hashtable KUnit test suite.
> +         It tests the basic functionality of the API defined in
> +         include/linux/hashtable.h. 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.
> +
>  config LINEAR_RANGES_TEST
>         tristate "KUnit test for linear_ranges"
>         depends on KUNIT
> diff --git a/lib/Makefile b/lib/Makefile
> index 4d9461bfea42..5f8efbe8e97f 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -369,6 +369,7 @@ obj-$(CONFIG_PLDMFW) += pldmfw/
>  CFLAGS_bitfield_kunit.o := $(DISABLE_STRUCTLEAK_PLUGIN)
>  obj-$(CONFIG_BITFIELD_KUNIT) += bitfield_kunit.o
>  obj-$(CONFIG_LIST_KUNIT_TEST) += list-test.o
> +obj-$(CONFIG_HASHTABLE_KUNIT_TEST) += hashtable_test.o
>  obj-$(CONFIG_LINEAR_RANGES_TEST) += test_linear_ranges.o
>  obj-$(CONFIG_BITS_TEST) += test_bits.o
>  obj-$(CONFIG_CMDLINE_KUNIT_TEST) += cmdline_kunit.o
> diff --git a/lib/hashtable_test.c b/lib/hashtable_test.c
> new file mode 100644
> index 000000000000..ab09b747d83d
> --- /dev/null
> +++ b/lib/hashtable_test.c
> @@ -0,0 +1,326 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * KUnit test for the Kernel Hashtable structures.
> + *
> + * Copyright (C) 2022, Google LLC.
> + * Author: Rae Moar <rmoar@...gle.com>
> + */
> +#include <kunit/test.h>
> +
> +#include <linux/hashtable.h>
> +
> +struct hashtable_test_entry {
> +       int key;
> +       int data;
> +       struct hlist_node node;
> +       int visited;
> +};
> +
> +static void hashtable_test_hash_init(struct kunit *test)
> +{
> +       /* Test the different ways of initialising a hashtable. */
> +       DEFINE_HASHTABLE(hash1, 3);
> +       DECLARE_HASHTABLE(hash2, 3);

As I understand it, DEFINE_HASHTABLE shouldn't need a hash_init(), but
DECLARE_HASHTABLE() does?

Could we make that clearer (and in so doing, get rid of the hash_init
for all hashtables which were DEFINE_HASHTABLE()ed?

> +
> +       hash_init(hash1);
> +       hash_init(hash2);
> +
> +       KUNIT_EXPECT_TRUE(test, hash_empty(hash1));
> +       KUNIT_EXPECT_TRUE(test, hash_empty(hash2));
> +}
> +
> +static void hashtable_test_hash_empty(struct kunit *test)
> +{
> +       struct hashtable_test_entry a;
> +       DEFINE_HASHTABLE(hash, 3);
> +
> +       hash_init(hash);
> +       KUNIT_EXPECT_TRUE(test, hash_empty(hash));
> +
> +       a.key = 1;
> +       a.data = 13;

I guess it doesn't matter what (if any) data is in 'a', so this isn't
strictly necessary. I don't mind having it though, as it's nice to
have some actual data to add.

If you really wanted, you could just add a struct hlist_node directly,
rather than struct hashtable_test_entry, though again, this is a more
realistic-looking test as-is, so I'm okay with keeping it.

> +       hash_add(hash, &a.node, a.key);
> +
> +       /* Hashtable should no longer be empty. */
> +       KUNIT_EXPECT_FALSE(test, hash_empty(hash));
> +}
> +
> +static void hashtable_test_hash_hashed(struct kunit *test)
> +{
> +       struct hashtable_test_entry a, b;
> +       DEFINE_HASHTABLE(hash, 3);
> +
> +       hash_init(hash);
> +       a.key = 1;
> +       a.data = 13;
> +       b.key = 1;
> +       b.data = 2;
> +

Nit: I might put the initialisation of the data in the same block as
adding them. Or possibly do something like:
a.key = 1;
a.data = …;
hash_add(…);
b.key = 1;
b.data = …;
hash_add(…);

Not something I actually care too much about, though: this is readable
enough as-is.

> +       hash_add(hash, &a.node, a.key);
> +       hash_add(hash, &b.node, b.key);
> +
> +       KUNIT_EXPECT_TRUE(test, hash_hashed(&a.node));
> +       KUNIT_EXPECT_TRUE(test, hash_hashed(&b.node));
> +}
> +
> +static void hashtable_test_hash_add(struct kunit *test)
> +{
> +       struct hashtable_test_entry a, b, *x;
> +       int bkt;
> +       DEFINE_HASHTABLE(hash, 3);
> +
> +       hash_init(hash);
> +       a.key = 1;
> +       a.data = 13;
> +       a.visited = 0;
> +       b.key = 2;
> +       b.data = 10;
> +       b.visited = 0;
> +
> +       hash_add(hash, &a.node, a.key);
> +       hash_add(hash, &b.node, b.key);

As above, can we reorder these to do everything with a, then
everything with b (and remove the hash_init)?

> +
> +       hash_for_each(hash, bkt, x, node) {
> +               x->visited++;
> +               if (x->key == a.key)
> +                       KUNIT_EXPECT_EQ(test, x->data, 13);
> +               else if (x->key == b.key)
> +                       KUNIT_EXPECT_EQ(test, x->data, 10);
> +               else
> +                       KUNIT_FAIL(test, "Unexpected key in hashtable.");
> +       }
> +
> +       /* Both entries should have been visited exactly once. */
> +       KUNIT_EXPECT_EQ(test, a.visited, 1);
> +       KUNIT_EXPECT_EQ(test, b.visited, 1);
> +}
> +
> +static void hashtable_test_hash_del(struct kunit *test)
> +{
> +       struct hashtable_test_entry a, b, *x;
> +       DEFINE_HASHTABLE(hash, 3);
> +
> +       hash_init(hash);
> +       a.key = 1;
> +       a.data = 13;
> +       b.key = 2;
> +       b.data = 10;
> +       b.visited = 0;
> +
> +       hash_add(hash, &a.node, a.key);
> +       hash_add(hash, &b.node, b.key);

As above, maybe adjust the spacing here. Though, to be honest, I don't
think it matters _quite_ as much once you get rid of hash_init().
Still probably better to do [init a][add a][init b][add b], IMO,
though.

> +
> +       hash_del(&b.node);
> +       hash_for_each_possible(hash, x, node, b.key) {
> +               x->visited++;
> +               KUNIT_EXPECT_NE(test, x->key, b.key);
> +       }
> +
> +       /* The deleted entry should not have been visited. */
> +       KUNIT_EXPECT_EQ(test, b.visited, 0);
> +
> +       hash_del(&a.node);
> +
> +       /* The hashtable should be empty. */
> +       KUNIT_EXPECT_TRUE(test, hash_empty(hash));
> +}
> +
> +static void hashtable_test_hash_for_each(struct kunit *test)
> +{
> +       struct hashtable_test_entry entries[3];
> +       struct hashtable_test_entry *x;
> +       int bkt, i, j, count;
> +       DEFINE_HASHTABLE(hash, 3);
> +
> +       /* Initialize a hashtable with three entries. */
> +       hash_init(hash);
> +       for (i = 0; i < 3; i++) {
> +               entries[i].key = i;
> +               entries[i].data = i + 10;
> +               entries[i].visited = 0;
> +               hash_add(hash, &entries[i].node, entries[i].key);
> +       }
> +
> +       count = 0;
> +       hash_for_each(hash, bkt, x, node) {
> +               x->visited += 1;
> +               KUNIT_ASSERT_GE(test, x->key, 0);
> +               KUNIT_ASSERT_LT(test, x->key, 3);
> +               count++;
> +       }
> +
> +       /* Should have visited each entry exactly once. */
> +       KUNIT_EXPECT_EQ(test, count, 3);
> +       for (j = 0; j < 3; j++)
> +               KUNIT_EXPECT_EQ(test, entries[j].visited, 1);
> +}
> +
> +static void hashtable_test_hash_for_each_safe(struct kunit *test)
> +{
> +       struct hashtable_test_entry entries[3];
> +       struct hashtable_test_entry *x;
> +       struct hlist_node *tmp;
> +       int bkt, i, j, count;
> +       DEFINE_HASHTABLE(hash, 3);
> +
> +       /* Initialize a hashtable with three entries. */
> +       hash_init(hash);
> +       for (i = 0; i < 3; i++) {
> +               entries[i].key = i;
> +               entries[i].data = i + 10;
> +               entries[i].visited = 0;
> +               hash_add(hash, &entries[i].node, entries[i].key);
> +       }
> +
> +       count = 0;
> +       hash_for_each_safe(hash, bkt, tmp, x, node) {
> +               x->visited += 1;
> +               KUNIT_ASSERT_GE(test, x->key, 0);
> +               KUNIT_ASSERT_LT(test, x->key, 3);
> +               count++;
> +
> +               /* Delete entry during loop. */
> +               hash_del(&x->node);
> +       }
> +
> +       /* Should have visited each entry exactly once. */
> +       KUNIT_EXPECT_EQ(test, count, 3);
> +       for (j = 0; j < 3; j++)
> +               KUNIT_EXPECT_EQ(test, entries[j].visited, 1);
> +}
> +
> +static void hashtable_test_hash_for_each_possible(struct kunit *test)
> +{
> +       struct hashtable_test_entry entries[4];
> +       struct hashtable_test_entry *x, *y;
> +       int buckets[2];
> +       int bkt, i, j, count;
> +       DEFINE_HASHTABLE(hash, 3);
> +
> +       /* Initialize a hashtable with three entries with key = 0. */
> +       hash_init(hash);
> +       for (i = 0; i < 3; i++) {
> +               entries[i].key = 0;
> +               entries[i].data = i;
> +               entries[i].visited = 0;
> +               hash_add(hash, &entries[i].node, entries[i].key);
> +       }
> +
> +       /* Add an entry with key = 1. */
> +       entries[3].key = 1;
> +       entries[3].data = 3;
> +       entries[3].visited = 0;
> +       hash_add(hash, &entries[3].node, entries[3].key);
> +
> +       count = 0;
> +       hash_for_each_possible(hash, x, node, 0) {
> +               x->visited += 1;
> +               KUNIT_ASSERT_GE(test, x->data, 0);
> +               KUNIT_ASSERT_LT(test, x->data, 4);
> +               count++;
> +       }
> +
> +       /* Should have visited each entry with key = 0 exactly once. */
> +       for (j = 0; j < 3; j++)
> +               KUNIT_EXPECT_EQ(test, entries[j].visited, 1);
> +
> +       /* Save the buckets for the different keys. */
> +       hash_for_each(hash, bkt, y, node) {
> +               if (y->key < 0 || y->key > 1)
> +                       KUNIT_ASSERT_FAILURE(test, "Unexpected key in hashtable.");

Nit: could we just use KUNIT_ASSERT_LEQ() and KUNIT_ASSERT_GEQ() here?
(Or better still, their _MSG variants)?

> +               buckets[y->key] = bkt;
> +       }
> +
> +       /* If entry with key = 1 is in the same bucket as the entries with
> +        * key = 0, check it was visited. Otherwise ensure that only three
> +        * entries were visited.
> +        */
> +       if (buckets[0] == buckets[1]) {
> +               KUNIT_EXPECT_EQ(test, count, 4);
> +               KUNIT_EXPECT_EQ(test, entries[3].visited, 1);
> +       } else {
> +               KUNIT_EXPECT_EQ(test, count, 3);
> +               KUNIT_EXPECT_EQ(test, entries[3].visited, 0);
> +       }
> +}
> +
> +static void hashtable_test_hash_for_each_possible_safe(struct kunit *test)
> +{
> +       struct hashtable_test_entry entries[4];
> +       struct hashtable_test_entry *x, *y;
> +       struct hlist_node *tmp;
> +       int buckets[2];
> +       int bkt, i, j, count;
> +       DEFINE_HASHTABLE(hash, 3);
> +
> +       /* Initialize a hashtable with three entries with key = 0. */
> +       hash_init(hash);
> +       for (i = 0; i < 3; i++) {
> +               entries[i].key = 0;
> +               entries[i].data = i;
> +               entries[i].visited = 0;
> +               hash_add(hash, &entries[i].node, entries[i].key);
> +       }
> +
> +       /* Add an entry with key = 1. */
> +       entries[3].key = 1;
> +       entries[3].data = 3;
> +       entries[3].visited = 0;
> +       hash_add(hash, &entries[3].node, entries[3].key);
> +
> +       count = 0;
> +       hash_for_each_possible_safe(hash, x, tmp, node, 0) {
> +               x->visited += 1;
> +               KUNIT_ASSERT_GE(test, x->data, 0);
> +               KUNIT_ASSERT_LT(test, x->data, 4);
> +               count++;
> +
> +               /* Delete entry during loop. */
> +               hash_del(&x->node);
> +       }
> +
> +       /* Should have visited each entry with key = 0 exactly once. */
> +       for (j = 0; j < 3; j++)
> +               KUNIT_EXPECT_EQ(test, entries[j].visited, 1);
> +
> +       /* Save the buckets for the different keys. */
> +       hash_for_each(hash, bkt, y, node) {
> +               if (y->key < 0 || y->key > 1)
> +                       KUNIT_ASSERT_FAILURE(test, "Unexpected key in hashtable.");

Nit: could we just use KUNIT_ASSERT_LEQ() and KUNIT_ASSERT_GEQ() here?
(Or better still, their _MSG variants)?

> +               buckets[y->key] = bkt;
> +       }
> +
> +       /* If entry with key = 1 is in the same bucket as the entries with
> +        * key = 0, check it was visited. Otherwise ensure that only three
> +        * entries were visited.
> +        */
> +       if (buckets[0] == buckets[1]) {
> +               KUNIT_EXPECT_EQ(test, count, 4);
> +               KUNIT_EXPECT_EQ(test, entries[3].visited, 1);
> +       } else {
> +               KUNIT_EXPECT_EQ(test, count, 3);
> +               KUNIT_EXPECT_EQ(test, entries[3].visited, 0);
> +       }
> +}
> +
> +static struct kunit_case hashtable_test_cases[] = {
> +       KUNIT_CASE(hashtable_test_hash_init),
> +       KUNIT_CASE(hashtable_test_hash_empty),
> +       KUNIT_CASE(hashtable_test_hash_hashed),
> +       KUNIT_CASE(hashtable_test_hash_add),
> +       KUNIT_CASE(hashtable_test_hash_del),
> +       KUNIT_CASE(hashtable_test_hash_for_each),
> +       KUNIT_CASE(hashtable_test_hash_for_each_safe),
> +       KUNIT_CASE(hashtable_test_hash_for_each_possible),
> +       KUNIT_CASE(hashtable_test_hash_for_each_possible_safe),
> +       {},
> +};
> +
> +static struct kunit_suite hashtable_test_module = {
> +       .name = "hashtable",
> +       .test_cases = hashtable_test_cases,
> +};
> +
> +kunit_test_suites(&hashtable_test_module);
> +
> +MODULE_LICENSE("GPL");
>
> base-commit: 88603b6dc419445847923fcb7fe5080067a30f98
> --
> 2.39.0.314.g84b9a713c41-goog
>

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