linux-kernel - Re: [PATCHv5 1/7] mm: drop page->slab

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Message-ID: <55ED1A09.3040409@gmail.com>
Date:	Sun, 6 Sep 2015 22:00:57 -0700
From:	Alexander Duyck <alexander.duyck@...il.com>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>
Cc:	Andrea Arcangeli <aarcange@...hat.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	David Rientjes <rientjes@...gle.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCHv5 1/7] mm: drop page->slab_page

On 09/03/2015 05:35 AM, Kirill A. Shutemov wrote:
> Since 8456a648cf44 ("slab: use struct page for slab management") nobody
> uses slab_page field in struct page.
>
> Let's drop it.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Acked-by: Christoph Lameter <cl@...ux.com>
> Acked-by: David Rientjes <rientjes@...gle.com>
> Acked-by: Vlastimil Babka <vbabka@...e.cz>
> Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
> Cc: Andi Kleen <ak@...ux.intel.com>
> ---
>   include/linux/mm_types.h |  1 -
>   mm/slab.c                | 17 +++--------------
>   2 files changed, 3 insertions(+), 15 deletions(-)
>
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 0038ac7466fd..58620ac7f15c 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -140,7 +140,6 @@ struct page {
>   #endif
>   		};
>   
> -		struct slab *slab_page; /* slab fields */
>   		struct rcu_head rcu_head;	/* Used by SLAB
>   						 * when destroying via RCU
>   						 */
> diff --git a/mm/slab.c b/mm/slab.c
> index 200e22412a16..649044f26e5d 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -1888,21 +1888,10 @@ static void slab_destroy(struct kmem_cache *cachep, struct page *page)
>   
>   	freelist = page->freelist;
>   	slab_destroy_debugcheck(cachep, page);
> -	if (unlikely(cachep->flags & SLAB_DESTROY_BY_RCU)) {
> -		struct rcu_head *head;
> -
> -		/*
> -		 * RCU free overloads the RCU head over the LRU.
> -		 * slab_page has been overloeaded over the LRU,
> -		 * however it is not used from now on so that
> -		 * we can use it safely.
> -		 */
> -		head = (void *)&page->rcu_head;
> -		call_rcu(head, kmem_rcu_free);
> -
> -	} else {
> +	if (unlikely(cachep->flags & SLAB_DESTROY_BY_RCU))
> +		call_rcu(&page->rcu_head, kmem_rcu_free);
> +	else
>   		kmem_freepages(cachep, page);
> -	}
>   
>   	/*
>   	 * From now on, we don't use freelist

This second piece looks like it belongs in patch 2, not patch 1 based on 
the descriptions.

- Alex
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