Received-SPF: pass (google.com: domain of linux-kernel+bounces-73393-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
From: Vlastimil Babka <vbabka@suse.cz>
Date: Tue, 20 Feb 2024 17:58:27 +0100
Subject: [PATCH 3/3] mm, slab, kasan: replace kasan_never_merge() with
 SLAB_NO_MERGE
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit
Message-Id: <20240220-slab-cleanup-flags-v1-3-e657e373944a@suse.cz>
References: <20240220-slab-cleanup-flags-v1-0-e657e373944a@suse.cz>
In-Reply-To: <20240220-slab-cleanup-flags-v1-0-e657e373944a@suse.cz>
To: Christoph Lameter <cl@linux.com>, Pekka Enberg <penberg@kernel.org>, 
 David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, 
 Andrew Morton <akpm@linux-foundation.org>, 
 Roman Gushchin <roman.gushchin@linux.dev>, 
 Hyeonggon Yoo <42.hyeyoo@gmail.com>, 
 Andrey Ryabinin <ryabinin.a.a@gmail.com>, 
 Alexander Potapenko <glider@google.com>, 
 Andrey Konovalov <andreyknvl@gmail.com>, Dmitry Vyukov <dvyukov@google.com>, 
 Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Zheng Yejian <zhengyejian1@huawei.com>, 
 Xiongwei Song <xiongwei.song@windriver.com>, 
 Chengming Zhou <chengming.zhou@linux.dev>, linux-mm@kvack.org, 
 linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, 
 Vlastimil Babka <vbabka@suse.cz>

The SLAB_KASAN flag prevents merging of caches in some configurations,
which is handled in a rather complicated way via kasan_never_merge().
Since we now have a generic SLAB_NO_MERGE flag, we can instead use it
for KASAN caches in addition to SLAB_KASAN in those configurations,
and simplify the SLAB_NEVER_MERGE handling.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 include/linux/kasan.h |  6 ------
 mm/kasan/generic.c    | 16 ++++------------
 mm/slab_common.c      |  2 +-
 3 files changed, 5 insertions(+), 19 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index dbb06d789e74..70d6a8f6e25d 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -429,7 +429,6 @@ struct kasan_cache {
 };
 
 size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object);
-slab_flags_t kasan_never_merge(void);
 void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
 			slab_flags_t *flags);
 
@@ -446,11 +445,6 @@ static inline size_t kasan_metadata_size(struct kmem_cache *cache,
 {
 	return 0;
 }
-/* And thus nothing prevents cache merging. */
-static inline slab_flags_t kasan_never_merge(void)
-{
-	return 0;
-}
 /* And no cache-related metadata initialization is required. */
 static inline void kasan_cache_create(struct kmem_cache *cache,
 				      unsigned int *size,
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index df6627f62402..d8b78d273b9f 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -334,14 +334,6 @@ DEFINE_ASAN_SET_SHADOW(f3);
 DEFINE_ASAN_SET_SHADOW(f5);
 DEFINE_ASAN_SET_SHADOW(f8);
 
-/* Only allow cache merging when no per-object metadata is present. */
-slab_flags_t kasan_never_merge(void)
-{
-	if (!kasan_requires_meta())
-		return 0;
-	return SLAB_KASAN;
-}
-
 /*
  * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
  * For larger allocations larger redzones are used.
@@ -372,13 +364,13 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
 	/*
 	 * SLAB_KASAN is used to mark caches that are sanitized by KASAN
 	 * and that thus have per-object metadata.
-	 * Currently this flag is used in two places:
+	 * Currently this flag is used in one place:
 	 * 1. In slab_ksize() to account for per-object metadata when
 	 *    calculating the size of the accessible memory within the object.
-	 * 2. In slab_common.c via kasan_never_merge() to prevent merging of
-	 *    caches with per-object metadata.
+	 * Additionally, we use SLAB_NO_MERGE to prevent merging of caches
+	 * with per-object metadata.
 	 */
-	*flags |= SLAB_KASAN;
+	*flags |= SLAB_KASAN | SLAB_NO_MERGE;
 
 	ok_size = *size;
 
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 238293b1dbe1..7cfa2f1ce655 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -50,7 +50,7 @@ static DECLARE_WORK(slab_caches_to_rcu_destroy_work,
  */
 #define SLAB_NEVER_MERGE (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
 		SLAB_TRACE | SLAB_TYPESAFE_BY_RCU | SLAB_NOLEAKTRACE | \
-		SLAB_FAILSLAB | SLAB_NO_MERGE | kasan_never_merge())
+		SLAB_FAILSLAB | SLAB_NO_MERGE)
 
 #define SLAB_MERGE_SAME (SLAB_RECLAIM_ACCOUNT | SLAB_CACHE_DMA | \
 			 SLAB_CACHE_DMA32 | SLAB_ACCOUNT)

-- 
2.43.1