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Date: Tue, 27 Dec 2022 18:00:18 -0800
From: Daniel Latypov <dlatypov@...gle.com>
To: Rae Moar <rmoar@...gle.com>
Cc: brendanhiggins@...gle.com, davidgow@...gle.com,
skhan@...uxfoundation.org, kunit-dev@...glegroups.com,
linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v1] lib/hashtable_test.c: add test for the hashtable structure
On Mon, Dec 19, 2022 at 7:16 PM 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>
Looks pretty good from a cursory glance.
Had some mostly stylistic nits/suggestions below.
> ---
>
> Note: The check patch script is outputting open brace errors on lines
> 154, 186, 231 of lib/hashtable_test.c but I believe the format of the
> braces on those lines is consistent with the Linux Kernel style guide.
> Will continue to look at these errors.
>
> lib/Kconfig.debug | 13 ++
> lib/Makefile | 1 +
> lib/hashtable_test.c | 299 +++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 313 insertions(+)
> create mode 100644 lib/hashtable_test.c
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 3fc7abffc7aa..3cf3b6f8cff4 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -2458,6 +2458,19 @@ 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 API and basic functionality of the functions
> + and associated macros defined in include/linux/hashtable.h.
nit: the "functions and associated macros" == "the API", so perhaps we
can shorten this a bit.
> + 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 161d6a724ff7..9036d3aeee0a 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -370,6 +370,7 @@ 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..7907df66a8e7
> --- /dev/null
> +++ b/lib/hashtable_test.c
> @@ -0,0 +1,299 @@
> +// 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);
> +
> + 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;
> + 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;
> +
> + 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);
> +
> + hash_for_each(hash, bkt, x, node) {
> + if (x->key == a.key && x->data == a.data)
> + a.visited += 1;
> + if (x->key == b.key && x->data == b.data)
> + b.visited += 1;
> + }
x->visited += 1;
or
x->visited++;
also do the same thing.
Note: given x is supposed to point to a or b, I don't know if checking
against a.data does us much good.
If we're trying to check that hash_add() doesn't mutate the keys and
data, this code won't catch it.
We'd have to instead do something like
if(x->key != 1 && x->key != 2) KUNIT_FAIL(test, ...);
> +
> + /* 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);
> +
> + hash_del(&b.node);
> + hash_for_each_possible(hash, x, node, b.key) {
> + if (x->key == b.key && x->data == b.data)
> + b.visited += 1;
Similarly to above, x->visited += 1 (or ++) is probably better.
> + }
> +
> + /* 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) {
> + if (x->key >= 0 && x->key < 3)
> + entries[x->key].visited += 1;
Would this be better using an assert to fail the test if we see unexpected keys?
E.g. like
if (x->key < 0 || x->key > 3) KUNIT_ASSERT_FAILURE(test, ...);
x->visited++;
count++;
or
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) {
> + if (x->key >= 0 && x->key < 3) {
> + entries[x->key].visited += 1;
> + hash_del(&entries[x->key].node);
> + }
> + 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_possible(struct kunit *test)
> +{
> + struct hashtable_test_entry entries[4];
> + struct hashtable_test_entry *x;
> + int i, j, count;
> + DEFINE_HASHTABLE(hash, 3);
> +
> + /* Initialize a hashtable with three entries with key = 1. */
> + hash_init(hash);
> + for (i = 0; i < 3; i++) {
> + entries[i].key = 1;
> + entries[i].data = i;
> + entries[i].visited = 0;
> + hash_add(hash, &entries[i].node, entries[i].key);
> + }
> +
> + /* Add an entry with key = 2. */
> + entries[3].key = 2;
> + 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, 1) {
> + if (x->data >= 0 && x->data < 4)
> + entries[x->data].visited += 1;
> + count++;
> + }
> +
> + /* Should have visited each entry with key = 1 exactly once. */
> + for (j = 0; j < 3; j++)
> + KUNIT_EXPECT_EQ(test, entries[j].visited, 1);
> +
> + /* If entry with key = 2 is in the same bucket as the entries with
> + * key = 1, check it was visited. Otherwise ensure that only three
> + * entries were visited.
> + */
> + if (hash_min(1, HASH_BITS(hash)) == hash_min(2, HASH_BITS(hash))) {
nit: this feels like we might be a bit too tied to the impl (not sure
if it'll change anytime soon, but still).
Could we check the bucket using hash_for_each?
E.g.
// assume we change the keys from {1,2} to {0,1}
int buckets[2];
hash_for_each(hash, bkt, x, node) {
buckets[x->key] = bkt;
}
if (buckets[0] == buckets[1]) { // all in the same bucket
...
} else { ... }
> + KUNIT_EXPECT_EQ(test, count, 4);
> + KUNIT_EXPECT_EQ(test, entries[3].visited, 1);
> + } else {
> + KUNIT_EXPECT_EQ(test, count, 3);
should we also check that entries[3].visited == 0?
Daniel
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