linux-kernel - Re: [PATCH] mm/slub: remove unused parameter in setup

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Message-ID: <61d43197-3ff4-d51a-d84f-fa5a41fcaf7d@suse.cz>
Date:   Mon, 11 Apr 2022 12:29:38 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     JaeSang Yoo <js.yoo.5b@...il.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>
Cc:     Ohhoon Kwon <ohkwon1043@...il.com>,
        Wonhyuk Yang <vvghjk1234@...il.com>,
        Jiyoup Kim <lakroforce@...il.com>,
        Donghyeok Kim <dthex5d@...il.com>,
        Christoph Lameter <clameter@....com>,
        JaeSang Yoo <jsyoo5b@...il.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/slub: remove unused parameter in setup_object*()

On 4/11/22 09:25, JaeSang Yoo wrote:
> setup_object_debug() and setup_object() has unused parameter, "struct
> slab *slab". Remove it.
> 
> By the commit 3ec0974210fe ("SLUB: Simplify debug code"),
> setup_object_debug() were introduced to refactor previous code blocks
> in the setup_object(). Previous code used SlabDebug() to init_object()
> and init_tracking(). As the SlabDebug() takes "struct page *page" as
> argument, the setup_object_debug() checks flag of "struct kmem_cache *s"
> which doesn't require "struct page *page".
> As the struct page were changed into struct slab by commit bb192ed9aa719
> ("mm/slub: Convert most struct page to struct slab by spatch"), but it's
> still unused parameter.
> 
> Suggested-by: Ohhoon Kwon <ohkwon1043@...il.com>
> Signed-off-by: JaeSang Yoo <jsyoo5b@...il.com>

Thanks, added.

> ---
>  mm/slub.c | 19 ++++++++-----------
>  1 file changed, 8 insertions(+), 11 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 9fe000fd19ca..273bbba74ca1 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -1264,8 +1264,7 @@ static inline void dec_slabs_node(struct kmem_cache *s, int node, int objects)
>  }
>  
>  /* Object debug checks for alloc/free paths */
> -static void setup_object_debug(struct kmem_cache *s, struct slab *slab,
> -								void *object)
> +static void setup_object_debug(struct kmem_cache *s, void *object)
>  {
>  	if (!kmem_cache_debug_flags(s, SLAB_STORE_USER|SLAB_RED_ZONE|__OBJECT_POISON))
>  		return;
> @@ -1631,8 +1630,7 @@ slab_flags_t kmem_cache_flags(unsigned int object_size,
>  	return flags | slub_debug_local;
>  }
>  #else /* !CONFIG_SLUB_DEBUG */
> -static inline void setup_object_debug(struct kmem_cache *s,
> -			struct slab *slab, void *object) {}
> +static inline void setup_object_debug(struct kmem_cache *s, void *object) {}
>  static inline
>  void setup_slab_debug(struct kmem_cache *s, struct slab *slab, void *addr) {}
>  
> @@ -1775,10 +1773,9 @@ static inline bool slab_free_freelist_hook(struct kmem_cache *s,
>  	return *head != NULL;
>  }
>  
> -static void *setup_object(struct kmem_cache *s, struct slab *slab,
> -				void *object)
> +static void *setup_object(struct kmem_cache *s, void *object)
>  {
> -	setup_object_debug(s, slab, object);
> +	setup_object_debug(s, object);
>  	object = kasan_init_slab_obj(s, object);
>  	if (unlikely(s->ctor)) {
>  		kasan_unpoison_object_data(s, object);
> @@ -1897,13 +1894,13 @@ static bool shuffle_freelist(struct kmem_cache *s, struct slab *slab)
>  	/* First entry is used as the base of the freelist */
>  	cur = next_freelist_entry(s, slab, &pos, start, page_limit,
>  				freelist_count);
> -	cur = setup_object(s, slab, cur);
> +	cur = setup_object(s, cur);
>  	slab->freelist = cur;
>  
>  	for (idx = 1; idx < slab->objects; idx++) {
>  		next = next_freelist_entry(s, slab, &pos, start, page_limit,
>  			freelist_count);
> -		next = setup_object(s, slab, next);
> +		next = setup_object(s, next);
>  		set_freepointer(s, cur, next);
>  		cur = next;
>  	}
> @@ -1974,11 +1971,11 @@ static struct slab *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
>  
>  	if (!shuffle) {
>  		start = fixup_red_left(s, start);
> -		start = setup_object(s, slab, start);
> +		start = setup_object(s, start);
>  		slab->freelist = start;
>  		for (idx = 0, p = start; idx < slab->objects - 1; idx++) {
>  			next = p + s->size;
> -			next = setup_object(s, slab, next);
> +			next = setup_object(s, next);
>  			set_freepointer(s, p, next);
>  			p = next;
>  		}