Re: [PATCH 5/6] introduce thp_ptep_get()

From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	David Rientjes <rientjes@google.com>,
	Andi Kleen <andi@firstfloor.org>,
	Wu Fengguang <fengguang.wu@intel.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/6] introduce thp_ptep_get()
Date: Mon, 30 Jan 2012 15:26:46 +0900	[thread overview]
Message-ID: <20120130152646.3f202259.kamezawa.hiroyu@jp.fujitsu.com> (raw)
In-Reply-To: <1327705373-29395-6-git-send-email-n-horiguchi@ah.jp.nec.com>

On Fri, 27 Jan 2012 18:02:52 -0500
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> wrote:

> Casting pmd into pte_t to handle thp is strongly architecture dependent.
> This patch introduces a new function to separate this dependency from
> independent part.
> 
> Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> ---
>  arch/x86/include/asm/pgtable.h |    5 +++++
>  fs/proc/task_mmu.c             |    4 ++--
>  include/asm-generic/pgtable.h  |    4 ++++
>  3 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git 3.3-rc1.orig/arch/x86/include/asm/pgtable.h 3.3-rc1/arch/x86/include/asm/pgtable.h
> index 49afb3f..4cfcc7e 100644
> --- 3.3-rc1.orig/arch/x86/include/asm/pgtable.h
> +++ 3.3-rc1/arch/x86/include/asm/pgtable.h
> @@ -165,6 +165,11 @@ static inline int has_transparent_hugepage(void)
>  {
>  	return cpu_has_pse;
>  }
> +
> +static inline pte_t thp_ptep_get(pmd_t *pmd)
> +{
> +	return *(pte_t *)pmd;
> +}

I'm sorry but I don't think the name is good. 
(But I know my sense of naming is bad ;)

How about pmd_to_pte_t ?

And, I wonder you can add error check as VM_BUG_ON(!pmd_trans_huge(*pmd));

Thanks,
-Kame

>  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>  
>  static inline pte_t pte_set_flags(pte_t pte, pteval_t set)
> diff --git 3.3-rc1.orig/fs/proc/task_mmu.c 3.3-rc1/fs/proc/task_mmu.c
> index 2622b64..e2063d9 100644
> --- 3.3-rc1.orig/fs/proc/task_mmu.c
> +++ 3.3-rc1/fs/proc/task_mmu.c
> @@ -395,7 +395,7 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
>  	spinlock_t *ptl;
>  
>  	if (pmd_trans_huge_lock(pmd, vma) == 1) {
> -		smaps_pte_entry(*(pte_t *)pmd, addr, HPAGE_PMD_SIZE, walk);
> +		smaps_pte_entry(thp_ptep_get(pmd), addr, HPAGE_PMD_SIZE, walk);
>  		spin_unlock(&walk->mm->page_table_lock);
>  		mss->anonymous_thp += HPAGE_PMD_SIZE;
>  		return 0;
> @@ -964,7 +964,7 @@ static int gather_pte_stats(pmd_t *pmd, unsigned long addr,
>  	md = walk->private;
>  
>  	if (pmd_trans_huge_lock(pmd, md->vma) == 1) {
> -		pte_t huge_pte = *(pte_t *)pmd;
> +		pte_t huge_pte = thp_ptep_get(pmd);
>  		struct page *page;
>  
>  		page = can_gather_numa_stats(huge_pte, md->vma, addr);
> diff --git 3.3-rc1.orig/include/asm-generic/pgtable.h 3.3-rc1/include/asm-generic/pgtable.h
> index 76bff2b..f346bdc 100644
> --- 3.3-rc1.orig/include/asm-generic/pgtable.h
> +++ 3.3-rc1/include/asm-generic/pgtable.h
> @@ -434,6 +434,10 @@ static inline int pmd_trans_splitting(pmd_t pmd)
>  {
>  	return 0;
>  }
> +static inline pte_t thp_ptep_get(pmd_t *pmd)
> +{
> +	return 0;
> +}
>  #ifndef __HAVE_ARCH_PMD_WRITE
>  static inline int pmd_write(pmd_t pmd)
>  {
> -- 
> 1.7.7.6
> 
> 