[PATCH 3/3] mm, slab, kasan: replace kasan_never_merge() with SLAB_NO_MERGE

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Vlastimil Babka

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Feb 20, 2024, 11:58:47 AMFeb 20
to Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim, Andrew Morton, Roman Gushchin, Hyeonggon Yoo, Andrey Ryabinin, Alexander Potapenko, Andrey Konovalov, Dmitry Vyukov, Vincenzo Frascino, Zheng Yejian, Xiongwei Song, Chengming Zhou, linu...@kvack.org, linux-...@vger.kernel.org, kasa...@googlegroups.com, Vlastimil Babka
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 <vba...@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

Song, Xiongwei

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Feb 20, 2024, 9:26:09 PMFeb 20
to Vlastimil Babka, Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim, Andrew Morton, Roman Gushchin, Hyeonggon Yoo, Andrey Ryabinin, Alexander Potapenko, Andrey Konovalov, Dmitry Vyukov, Vincenzo Frascino, Zheng Yejian, Chengming Zhou, linu...@kvack.org, linux-...@vger.kernel.org, kasa...@googlegroups.com

> 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 <vba...@suse.cz>

Ran a rough test with build and bootup with CONFIG_KASAN_GENERIC enabled,
feel free to add

Tested-by: Xiongwei Song <xiongw...@windriver.com>

Thanks,
Xiongwei

Chengming Zhou

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Feb 21, 2024, 2:15:24 AMFeb 21
to Vlastimil Babka, Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim, Andrew Morton, Roman Gushchin, Hyeonggon Yoo, Andrey Ryabinin, Alexander Potapenko, Andrey Konovalov, Dmitry Vyukov, Vincenzo Frascino, Zheng Yejian, Xiongwei Song, linu...@kvack.org, linux-...@vger.kernel.org, kasa...@googlegroups.com
On 2024/2/21 00:58, Vlastimil Babka wrote:
> 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 <vba...@suse.cz>

Reviewed-by: Chengming Zhou <chengmi...@linux.dev>

Thanks!

Andrey Konovalov

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Feb 21, 2024, 3:49:13 PMFeb 21
to Vlastimil Babka, Christoph Lameter, Pekka Enberg, David Rientjes, Joonsoo Kim, Andrew Morton, Roman Gushchin, Hyeonggon Yoo, Andrey Ryabinin, Alexander Potapenko, Dmitry Vyukov, Vincenzo Frascino, Zheng Yejian, Xiongwei Song, Chengming Zhou, linu...@kvack.org, linux-...@vger.kernel.org, kasa...@googlegroups.com
Let's reword this to:

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
slab_ksize() to account for per-object metadata when calculating the
size of the accessible memory within the object.

> + * 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
>

Otherwise, looks good to me.

Reviewed-by: Andrey Konovalov <andre...@gmail.com>

Thanks!
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