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Date: Fri, 13 Jan 2023 17:23:10 -0500
From: Rae Moar <rmoar@...gle.com>
To: Daniel Latypov <dlatypov@...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 Tue, Dec 27, 2022 at 9:00 PM Daniel Latypov <dlatypov@...gle.com> wrote:
>
> 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.
This seems better to me. Thanks!
>
> > + 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.
Oh right. That makes a lot of sense.
>
> 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, ...);
>
This seems like a good change to me in combination with changing it to
x->visited++;.
Although David's suggestion might be slightly more exhaustive.
Why wouldn't it be important to check that the key matches the data?
> > +
> > + /* 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.
Right. Will switch this out here.
>
> > + }
> > +
> > + /* 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);
Yes, this makes a lot of sense. I will switch out just the if
statements for using assert statements.
>
> > + 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 { ... }
I really like the idea of using hash_for_each to determine the bucket.
I will add this to the test.
>
> > + 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?
Right. Must have been a mistake on my end. Oops.
>
> Daniel
Thanks Daniel!
-Rae
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