linux-kernel - Re: [PATCH][mm/memory.c]: transparent hugepage check condition missed

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Date:	Tue, 01 Nov 2011 09:18:08 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	Guanjun He <gjhe@...e.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][mm/memory.c]: transparent hugepage check condition
 missed

On Mon, 2011-10-31 at 16:23 +0800, Guanjun He wrote:
> For the transparent hugepage module still does not support
> tmpfs and cache,the check condition should always be checked 
> to make sure that it only affect the anonymous maps, the 
> original check condition missed this, this patch is to fix this.
> Otherwise,the hugepage may affect the file-backed maps,
> then the cache for the small-size pages will be unuseful,
> and till now there is still no implementation for hugepage's cache.
> 
> Signed-off-by: Guanjun He <gjhe@...e.com>
> ---
>  mm/memory.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index a56e3ba..79b85fe 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3475,7 +3475,8 @@ int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
>  		if (pmd_trans_huge(orig_pmd)) {
>  			if (flags & FAULT_FLAG_WRITE &&
>  			    !pmd_write(orig_pmd) &&
> -			    !pmd_trans_splitting(orig_pmd))
> +			    !pmd_trans_splitting(orig_pmd) &&
> +			    !vma->vm_ops)
>  				return do_huge_pmd_wp_page(mm, vma, address,
>  							   pmd, orig_pmd);
>  			return 0;
so if vma->vm_ops != NULL, how could the pmd_trans_huge(orig_pmd) be
true? We never enable THP if vma->vm_ops != NULL.

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