linux-kernel - Re: [PATCH 05/10] migrate: add hugepage migration code to migrate

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Date:	Mon, 25 Mar 2013 14:04:16 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>, Hugh Dickins <hughd@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andi Kleen <andi@...stfloor.org>,
	Hillf Danton <dhillf@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/10] migrate: add hugepage migration code to
 migrate_pages()

On Fri 22-03-13 16:23:50, Naoya Horiguchi wrote:
[...]
> @@ -523,6 +544,11 @@ static inline int check_pmd_range(struct vm_area_struct *vma, pud_t *pud,
>  	pmd = pmd_offset(pud, addr);
>  	do {
>  		next = pmd_addr_end(addr, end);
> +		if (pmd_huge(*pmd) && is_vm_hugetlb_page(vma)) {
> +			check_hugetlb_pmd_range(vma, pmd, nodes,
> +						flags, private);

I am afraid this has the same issue with other huge page sizes I have
mentioned earlier.

> +			continue;
> +		}
>  		split_huge_page_pmd(vma, addr, pmd);
>  		if (pmd_none_or_trans_huge_or_clear_bad(pmd))
>  			continue;
[...]
> @@ -1012,14 +1040,8 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
>  	check_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
>  			flags | MPOL_MF_DISCONTIG_OK, &pagelist);
>  
> -	if (!list_empty(&pagelist)) {
> -		err = migrate_pages(&pagelist, new_node_page, dest,
> +	return migrate_movable_pages(&pagelist, new_node_page, dest,
>  					MIGRATE_SYNC, MR_SYSCALL);
> -		if (err)
> -			putback_lru_pages(&pagelist);
> -	}
> -
> -	return err;

This is really confusing. Why migrate_pages doesn't do putback cleanup
on its own but migrate_movable_pages does?
Please also move migrate_movable_pages definition to this patch.

>  }
>  
>  /*
> -- 
> 1.7.11.7
> 

-- 
Michal Hocko
SUSE Labs
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