linux-kernel - [PATCH mm-unstable] mm/kasan: use SLAB_NO_MERGE flag instead of an empty constructor

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Message-ID: <20250318015926.1629748-1-harry.yoo@oracle.com>
Date: Tue, 18 Mar 2025 10:59:26 +0900
From: Harry Yoo <harry.yoo@...cle.com>
To: Andrey Ryabinin <ryabinin.a.a@...il.com>
Cc: Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Andrew Morton <akpm@...ux-foundation.org>, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Harry Yoo <harry.yoo@...cle.com>
Subject: [PATCH mm-unstable] mm/kasan: use SLAB_NO_MERGE flag instead of an empty constructor

Use SLAB_NO_MERGE flag to prevent merging instead of providing an
empty constructor. Using an empty constructor in this manner is an abuse
of slab interface.

The SLAB_NO_MERGE flag should be used with caution, but in this case,
it is acceptable as the cache is intended solely for debugging purposes.

No functional changes intended.

Signed-off-by: Harry Yoo <harry.yoo@...cle.com>
---
 mm/kasan/kasan_test_c.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/mm/kasan/kasan_test_c.c b/mm/kasan/kasan_test_c.c
index 59d673400085..3ea317837c2d 100644
--- a/mm/kasan/kasan_test_c.c
+++ b/mm/kasan/kasan_test_c.c
@@ -1073,14 +1073,11 @@ static void kmem_cache_rcu_uaf(struct kunit *test)
 	kmem_cache_destroy(cache);
 }
 
-static void empty_cache_ctor(void *object) { }
-
 static void kmem_cache_double_destroy(struct kunit *test)
 {
 	struct kmem_cache *cache;
 
-	/* Provide a constructor to prevent cache merging. */
-	cache = kmem_cache_create("test_cache", 200, 0, 0, empty_cache_ctor);
+	cache = kmem_cache_create("test_cache", 200, 0, SLAB_NO_MERGE, NULL);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, cache);
 	kmem_cache_destroy(cache);
 	KUNIT_EXPECT_KASAN_FAIL(test, kmem_cache_destroy(cache));
-- 
2.43.0