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Date: Thu, 6 Jun 2024 10:35:54 +0200
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Subject: Re: [PATCH v2 3/3] slab: delete useless RED_INACTIVE and RED_ACTIVE
Content-Language: en-US
To: Chengming Zhou <chengming.zhou@linux.dev>,
 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>, Feng Tang <feng.tang@intel.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
 zhouchengming@bytedance.com
References: <20240605-b4-slab-debug-v2-0-c535b9cd361c@linux.dev>
 <20240605-b4-slab-debug-v2-3-c535b9cd361c@linux.dev>
From: Vlastimil Babka <vbabka@suse.cz>
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In-Reply-To: <20240605-b4-slab-debug-v2-3-c535b9cd361c@linux.dev>
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On 6/5/24 9:13 AM, Chengming Zhou wrote:
> These seem useless since we use the SLUB_RED_INACTIVE and SLUB_RED_ACTIVE,
> so just delete them, no functional change.
> 
> Signed-off-by: Chengming Zhou <chengming.zhou@linux.dev>

Reviewed-by: Vlastimil Babka <vbabka@suse.cz>

> ---
>  include/linux/poison.h       | 7 ++-----
>  mm/slub.c                    | 4 ++--
>  tools/include/linux/poison.h | 7 ++-----
>  3 files changed, 6 insertions(+), 12 deletions(-)
> 
> diff --git a/include/linux/poison.h b/include/linux/poison.h
> index 1f0ee2459f2a..9c1a035af97c 100644
> --- a/include/linux/poison.h
> +++ b/include/linux/poison.h
> @@ -38,11 +38,8 @@
>   * Magic nums for obj red zoning.
>   * Placed in the first word before and the first word after an obj.
>   */
> -#define	RED_INACTIVE	0x09F911029D74E35BULL	/* when obj is inactive */
> -#define	RED_ACTIVE	0xD84156C5635688C0ULL	/* when obj is active */
> -
> -#define SLUB_RED_INACTIVE	0xbb
> -#define SLUB_RED_ACTIVE		0xcc
> +#define SLUB_RED_INACTIVE	0xbb	/* when obj is inactive */
> +#define SLUB_RED_ACTIVE		0xcc	/* when obj is active */
>  
>  /* ...and for poisoning */
>  #define	POISON_INUSE	0x5a	/* for use-uninitialised poisoning */
> diff --git a/mm/slub.c b/mm/slub.c
> index 704c662227e6..0bab0f041ab2 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -1214,8 +1214,8 @@ static int check_bytes_and_report(struct kmem_cache *s, struct slab *slab,
>   * 	Padding is extended by another word if Redzoning is enabled and
>   * 	object_size == inuse.
>   *
> - * 	We fill with 0xbb (RED_INACTIVE) for inactive objects and with
> - * 	0xcc (RED_ACTIVE) for objects in use.
> + * 	We fill with 0xbb (SLUB_RED_INACTIVE) for inactive objects and with
> + * 	0xcc (SLUB_RED_ACTIVE) for objects in use.
>   *
>   * object + s->inuse
>   * 	Meta data starts here.
> diff --git a/tools/include/linux/poison.h b/tools/include/linux/poison.h
> index 2e6338ac5eed..e530e54046c9 100644
> --- a/tools/include/linux/poison.h
> +++ b/tools/include/linux/poison.h
> @@ -47,11 +47,8 @@
>   * Magic nums for obj red zoning.
>   * Placed in the first word before and the first word after an obj.
>   */
> -#define	RED_INACTIVE	0x09F911029D74E35BULL	/* when obj is inactive */
> -#define	RED_ACTIVE	0xD84156C5635688C0ULL	/* when obj is active */
> -
> -#define SLUB_RED_INACTIVE	0xbb
> -#define SLUB_RED_ACTIVE		0xcc
> +#define SLUB_RED_INACTIVE	0xbb	/* when obj is inactive */
> +#define SLUB_RED_ACTIVE		0xcc	/* when obj is active */
>  
>  /* ...and for poisoning */
>  #define	POISON_INUSE	0x5a	/* for use-uninitialised poisoning */
>