linux-kernel - Re: [RFC/PATCH 3/5] mm: get_user_pages: use NON-MOVABLE pages when FOLL

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Message-ID: <51370CC7.8050406@cn.fujitsu.com>
Date:	Wed, 06 Mar 2013 17:30:47 +0800
From:	Lin Feng <linfeng@...fujitsu.com>
To:	Marek Szyprowski <m.szyprowski@...sung.com>
CC:	linux-mm@...ck.org, linaro-mm-sig@...ts.linaro.org,
	linux-kernel@...r.kernel.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Arnd Bergmann <arnd@...db.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>,
	Michal Nazarewicz <mina86@...a86.com>,
	Minchan Kim <minchan@...nel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [RFC/PATCH 3/5] mm: get_user_pages: use NON-MOVABLE pages when
 FOLL_DURABLE flag is set

Hi Marek,

On 03/05/2013 02:57 PM, Marek Szyprowski wrote:
> @@ -2495,7 +2498,7 @@ static inline void cow_user_page(struct page *dst, struct page *src, unsigned lo
>   */
>  static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
>  		unsigned long address, pte_t *page_table, pmd_t *pmd,
> -		spinlock_t *ptl, pte_t orig_pte)
> +		spinlock_t *ptl, pte_t orig_pte, unsigned int flags)
>  	__releases(ptl)
>  {
>  	struct page *old_page, *new_page = NULL;
> @@ -2505,6 +2508,10 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
>  	struct page *dirty_page = NULL;
>  	unsigned long mmun_start = 0;	/* For mmu_notifiers */
>  	unsigned long mmun_end = 0;	/* For mmu_notifiers */
> +	gfp_t gfp = GFP_HIGHUSER_MOVABLE;
> +
> +	if (IS_ENABLED(CONFIG_CMA) && (flags & FAULT_FLAG_NO_CMA))
> +		gfp &= ~__GFP_MOVABLE;

Here just simply strip the __GFP_MOVABLE flag, IIUC it will break the page migrate policy.  
Because " But GFP_MOVABLE is not only a zone specifier but also an allocation policy.".

Another problem is that you add a new flag to instruct the page allocation, 
do we have to also handle the hugepage or THP as Mel ever mentioned?
 
thanks,
linfeng
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