[PATCH v2 6/6] slub_kunit: Add a test for the kmalloc_partition boot parameter

[Chris Down <chris@chrisdown.name>]

Check that the kmalloc partitions are separate caches by default, and
alias the normal kmalloc caches when they're turned off with
kmalloc_partition=0.

Signed-off-by: Chris Down <chris@chrisdown.name>
---
 lib/tests/slub_kunit.c | 46 ++++++++++++++++++++++++++++++++++++++++++
 mm/slab.h              |  4 ++++
 mm/slab_common.c       |  3 ++-
 3 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/lib/tests/slub_kunit.c b/lib/tests/slub_kunit.c
index 670645875b27..e3035864577d 100644
--- a/lib/tests/slub_kunit.c
+++ b/lib/tests/slub_kunit.c
@@ -333,6 +333,49 @@ static void test_slab_buckets(struct kunit *test)
 }
 #endif
 
+#ifdef CONFIG_KMALLOC_PARTITION_CACHES
+/*
+ * Each partition copy is a separate cache, unless the copies were disabled
+ * with kmalloc_partition=0: then they alias the KMALLOC_NORMAL caches.
+ */
+static void test_kmalloc_partition(struct kunit *test)
+{
+	enum kmalloc_cache_type type;
+	struct kmem_cache *s;
+	unsigned int idx;
+	bool found;
+	void *p;
+
+	for (type = KMALLOC_PARTITION_START + 1; type <= KMALLOC_PARTITION_END; type++) {
+		for (idx = 0; idx < ARRAY_SIZE(kmalloc_caches[type]); idx++) {
+			struct kmem_cache *normal = kmalloc_caches[KMALLOC_NORMAL][idx];
+			struct kmem_cache *part = kmalloc_caches[type][idx];
+
+			if (!kmalloc_partition_enabled) {
+				KUNIT_EXPECT_PTR_EQ(test, part, normal);
+			} else if (normal) {
+				KUNIT_EXPECT_NOT_NULL(test, part);
+				KUNIT_EXPECT_PTR_NE(test, part, normal);
+			}
+		}
+	}
+
+	p = kmalloc(64, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, p);
+	s = virt_to_slab(p)->slab_cache;
+	idx = kmalloc_index(64);
+	if (!kmalloc_partition_enabled) {
+		KUNIT_EXPECT_PTR_EQ(test, s, kmalloc_caches[KMALLOC_NORMAL][idx]);
+	} else {
+		found = false;
+		for (type = KMALLOC_PARTITION_START; type <= KMALLOC_PARTITION_END; type++)
+			found |= s == kmalloc_caches[type][idx];
+		KUNIT_EXPECT_TRUE_MSG(test, found, "allocated from %s", s->name);
+	}
+	kfree(p);
+}
+#endif
+
 #if defined(CONFIG_PERF_EVENTS) || (defined(CONFIG_KPROBES) && defined(CONFIG_SMP))
 #define NR_ITERATIONS 1000
 #define NR_OBJECTS 1000
@@ -529,6 +572,9 @@ static struct kunit_case test_cases[] = {
 #ifdef CONFIG_SLAB_BUCKETS
 	KUNIT_CASE(test_slab_buckets),
 #endif
+#ifdef CONFIG_KMALLOC_PARTITION_CACHES
+	KUNIT_CASE(test_kmalloc_partition),
+#endif
 #ifdef CONFIG_PERF_EVENTS
 	KUNIT_CASE_SLOW(test_kmalloc_nolock_and_friends_perf),
 #endif
diff --git a/mm/slab.h b/mm/slab.h
index b5b344d6e402..8e1e5a3f044b 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -394,6 +394,10 @@ extern struct kmem_cache *kmem_cache;
 extern bool slab_buckets_enabled;
 #endif
 
+#if IS_ENABLED(CONFIG_KUNIT) && defined(CONFIG_KMALLOC_PARTITION_CACHES)
+extern bool kmalloc_partition_enabled;
+#endif
+
 /* A table of kmalloc cache names and sizes */
 extern const struct kmalloc_info_struct {
 	const char *name[NR_KMALLOC_TYPES];
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 5391149a2eed..406e8688ee0e 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -782,7 +782,8 @@ EXPORT_SYMBOL(random_kmalloc_seed);
 #endif
 
 #ifdef CONFIG_KMALLOC_PARTITION_CACHES
-static bool kmalloc_partition_enabled __ro_after_init = true;
+VISIBLE_IF_KUNIT bool kmalloc_partition_enabled __ro_after_init = true;
+EXPORT_SYMBOL_IF_KUNIT(kmalloc_partition_enabled);
 
 static int __init setup_kmalloc_partition(char *str)
 {
-- 
2.54.0