Re: [PATCH mm v3 09/19] kasan: open-code kasan_unpoison_slab

From: Marco Elver <elver@google.com>
To: Andrey Konovalov <andreyknvl@google.com>
Cc: linux-arm-kernel@lists.infradead.org,
	Branislav Rankov <Branislav.Rankov@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Kevin Brodsky <kevin.brodsky@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
	linux-mm@kvack.org, Alexander Potapenko <glider@google.com>,
	Evgenii Stepanov <eugenis@google.com>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Dmitry Vyukov <dvyukov@google.com>
Subject: Re: [PATCH mm v3 09/19] kasan: open-code kasan_unpoison_slab
Date: Mon, 16 Nov 2020 16:06:07 +0100	[thread overview]
Message-ID: <20201116150607.GA1357314@elver.google.com> (raw)
In-Reply-To: <4d64025c647190a8b7101d0b1da3deb922535a0d.1605305978.git.andreyknvl@google.com>

On Fri, Nov 13, 2020 at 11:19PM +0100, Andrey Konovalov wrote:
> There's the external annotation kasan_unpoison_slab() that is currently
> defined as static inline and uses kasan_unpoison_range(). Open-code this
> function in mempool.c. Otherwise with an upcoming change this function
> will result in an unnecessary function call.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> Link: https://linux-review.googlesource.com/id/Ia7c8b659f79209935cbaab3913bf7f082cc43a0e

Reviewed-by: Marco Elver <elver@google.com>

Thank you!

I also think this change made the code more readable, as
kasan_unpoison_slab() made me think it's unpoisoning the *whole* slab,
which is clearly not the case.

> ---
>  include/linux/kasan.h | 6 ------
>  mm/mempool.c          | 2 +-
>  2 files changed, 1 insertion(+), 7 deletions(-)
> 
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index 1594177f86bb..872bf145ddde 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -106,11 +106,6 @@ struct kasan_cache {
>  	int free_meta_offset;
>  };
>  
> -size_t __ksize(const void *);
> -static inline void kasan_unpoison_slab(const void *ptr)
> -{
> -	kasan_unpoison_range(ptr, __ksize(ptr));
> -}
>  size_t kasan_metadata_size(struct kmem_cache *cache);
>  
>  bool kasan_save_enable_multi_shot(void);
> @@ -166,7 +161,6 @@ static inline bool kasan_slab_free(struct kmem_cache *s, void *object,
>  	return false;
>  }
>  
> -static inline void kasan_unpoison_slab(const void *ptr) { }
>  static inline size_t kasan_metadata_size(struct kmem_cache *cache) { return 0; }
>  
>  #endif /* CONFIG_KASAN */
> diff --git a/mm/mempool.c b/mm/mempool.c
> index f473cdddaff0..583a9865b181 100644
> --- a/mm/mempool.c
> +++ b/mm/mempool.c
> @@ -112,7 +112,7 @@ static __always_inline void kasan_poison_element(mempool_t *pool, void *element)
>  static void kasan_unpoison_element(mempool_t *pool, void *element)
>  {
>  	if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)
> -		kasan_unpoison_slab(element);
> +		kasan_unpoison_range(element, __ksize(element));
>  	else if (pool->alloc == mempool_alloc_pages)
>  		kasan_alloc_pages(element, (unsigned long)pool->pool_data);
>  }
> -- 
> 2.29.2.299.gdc1121823c-goog
> 

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