linux-kernel - Re: [PATCH] mm: hugetlb: flush dcache before returning zeroed huge page to userspace

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Date:	Thu, 16 Aug 2012 20:20:15 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Will Deacon <will.deacon@....com>
Cc:	Hugh Dickins <hughd@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hillf Danton <dhillf@...il.com>,
	Russell King <linux@....linux.org.uk>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: hugetlb: flush dcache before returning zeroed huge
 page to userspace

On Thu 16-08-12 17:09:54, Will Deacon wrote:
> On Wed, Aug 08, 2012 at 05:26:07PM +0100, Michal Hocko wrote:
[...]
> diff --git a/arch/ia64/include/asm/hugetlb.h b/arch/ia64/include/asm/hugetlb.h
> index da55c63..2adaa60 100644
> --- a/arch/ia64/include/asm/hugetlb.h
> +++ b/arch/ia64/include/asm/hugetlb.h
> @@ -1,6 +1,7 @@
>  #ifndef _ASM_IA64_HUGETLB_H
>  #define _ASM_IA64_HUGETLB_H
>  
> +#include <asm/cacheflush.h>
>  #include <asm/page.h>
>  
>  
> @@ -77,4 +78,9 @@ static inline void arch_release_hugepage(struct page *page)
>  {
>  }
>  
> +static inline void arch_clear_hugepage_flags(struct page *page)
> +{
> +	flush_dcache_page(page);
> +}
> +

Why do we need the hook for ia64? hugetlb_no_page calls clear_huge_page
and that one calls flush_dcache_page (via clear_user_page), right?
The same applies to copy_huge_page for COW.

> diff --git a/arch/powerpc/include/asm/hugetlb.h b/arch/powerpc/include/asm/hugetlb.h
> index dfdb95b..52696e6 100644
> --- a/arch/powerpc/include/asm/hugetlb.h
> +++ b/arch/powerpc/include/asm/hugetlb.h
> @@ -2,6 +2,7 @@
>  #define _ASM_POWERPC_HUGETLB_H
>  
>  #ifdef CONFIG_HUGETLB_PAGE
> +#include <asm/cacheflush.h>
>  #include <asm/page.h>
>  
>  extern struct kmem_cache *hugepte_cache;
> @@ -151,6 +152,11 @@ static inline void arch_release_hugepage(struct page *page)
>  {
>  }
>  
> +static inline void arch_clear_hugepage_flags(struct page *page)
> +{
> +	flush_dcache_page(page);
> +}
> +

Same here

-- 
Michal Hocko
SUSE Labs
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