linux-kernel - Re: [PATCH 2/9] slab: makes clear_obj_pfmemalloc() just return store masked value

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Message-ID: <alpine.DEB.2.10.1402141225460.12887@nuc>
Date:	Fri, 14 Feb 2014 12:27:10 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
cc:	Pekka Enberg <penberg@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Joonsoo Kim <js1304@...il.com>
Subject: Re: [PATCH 2/9] slab: makes clear_obj_pfmemalloc() just return store
 masked value

On Fri, 14 Feb 2014, Joonsoo Kim wrote:

> clear_obj_pfmemalloc() takes the pointer to the object pointer as argument
> to store masked value back into this address.
> But this is useless, since we don't use this stored value anymore.
> All we need is just masked value. So makes clear_obj_pfmemalloc()
> just return masked value.

Could this be a bit more compact?

> @@ -215,9 +215,9 @@ static inline void set_obj_pfmemalloc(void **objp)
>  	return;
>  }
>
> -static inline void clear_obj_pfmemalloc(void **objp)
> +static inline void *clear_obj_pfmemalloc(void *objp)
>  {
> -	*objp = (void *)((unsigned long)*objp & ~SLAB_OBJ_PFMEMALLOC);
> +	return (void *)((unsigned long)objp & ~SLAB_OBJ_PFMEMALLOC);
>  }

I dont think you need the (void *) cast here.

>  /*
> @@ -810,7 +810,7 @@ static void *__ac_get_obj(struct kmem_cache *cachep, struct array_cache *ac,
>  		struct kmem_cache_node *n;
>
>  		if (gfp_pfmemalloc_allowed(flags)) {
> -			clear_obj_pfmemalloc(&objp);
> +			objp = clear_obj_pfmemalloc(objp);
>  			return objp;
>  		}

No need for objp. Just "return clear_obj_....


> @@ -833,7 +833,7 @@ static void *__ac_get_obj(struct kmem_cache *cachep, struct array_cache *ac,
>  		if (!list_empty(&n->slabs_free) && force_refill) {
>  			struct page *page = virt_to_head_page(objp);
>  			ClearPageSlabPfmemalloc(page);
> -			clear_obj_pfmemalloc(&objp);
> +			objp = clear_obj_pfmemalloc(objp);
>  			recheck_pfmemalloc_active(cachep, ac);
>  			return objp;

Same here?
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