linux-kernel - Re: [PATCH v2 09/12] mm: hwpoison: soft offline supports thp migration

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Date:   Thu, 10 Nov 2016 21:31:10 +1100
From:   Balbir Singh <bsingharora@...il.com>
To:     Naoya Horiguchi <n-horiguchi@...jp.nec.com>, linux-mm@...ck.org
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Hugh Dickins <hughd@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michal Hocko <mhocko@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Pavel Emelyanov <xemul@...allels.com>,
        Zi Yan <zi.yan@...rutgers.edu>, linux-kernel@...r.kernel.org,
        Naoya Horiguchi <nao.horiguchi@...il.com>
Subject: Re: [PATCH v2 09/12] mm: hwpoison: soft offline supports thp
 migration



On 08/11/16 10:31, Naoya Horiguchi wrote:
> This patch enables thp migration for soft offline.
> 
> Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> ---
>  mm/memory-failure.c | 31 ++++++++++++-------------------
>  1 file changed, 12 insertions(+), 19 deletions(-)
> 
> diff --git v4.9-rc2-mmotm-2016-10-27-18-27/mm/memory-failure.c v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/memory-failure.c
> index 19e796d..6cc8157 100644
> --- v4.9-rc2-mmotm-2016-10-27-18-27/mm/memory-failure.c
> +++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/memory-failure.c
> @@ -1485,7 +1485,17 @@ static struct page *new_page(struct page *p, unsigned long private, int **x)
>  	if (PageHuge(p))
>  		return alloc_huge_page_node(page_hstate(compound_head(p)),
>  						   nid);
> -	else
> +	else if (thp_migration_supported() && PageTransHuge(p)) {
> +		struct page *thp;
> +
> +		thp = alloc_pages_node(nid,
> +			(GFP_TRANSHUGE | __GFP_THISNODE) & ~__GFP_RECLAIM,
> +			HPAGE_PMD_ORDER);
> +		if (!thp)
> +			return NULL;

Just wondering if new_page() fails, migration of that entry fails. Do we then
split and migrate? I guess this applies to THP migration in general.

Balbir Singh