linux-kernel - Re: [PATCH 01/18] mm, hugetlb: protect reserved pages when softofflining requests the pages

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Date:	Tue, 30 Jul 2013 22:19:28 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Michal Hocko <mhocko@...e.cz>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Hugh Dickins <hughd@...gle.com>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	David Gibson <david@...son.dropbear.id.au>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Joonsoo Kim <js1304@...il.com>,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Hillf Danton <dhillf@...il.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH 01/18] mm, hugetlb: protect reserved pages when softofflining requests the pages

Joonsoo Kim <iamjoonsoo.kim@....com> writes:

> alloc_huge_page_node() use dequeue_huge_page_node() without
> any validation check, so it can steal reserved page unconditionally.
> To fix it, check the number of free_huge_page in
> alloc_huge_page_node().


May be we should say. Don't use the reserve pool when soft offlining a huge
page. Check we have free pages outside the reserve pool before we
dequeue the huge page 

Reviewed-by: Aneesh Kumar <aneesh.kumar@...ux.vnet.ibm.com>


>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 6782b41..d971233 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -935,10 +935,11 @@ static struct page *alloc_buddy_huge_page(struct hstate *h, int nid)
>   */
>  struct page *alloc_huge_page_node(struct hstate *h, int nid)
>  {
> -	struct page *page;
> +	struct page *page = NULL;
>
>  	spin_lock(&hugetlb_lock);
> -	page = dequeue_huge_page_node(h, nid);
> +	if (h->free_huge_pages - h->resv_huge_pages > 0)
> +		page = dequeue_huge_page_node(h, nid);
>  	spin_unlock(&hugetlb_lock);
>
>  	if (!page)
> -- 
> 1.7.9.5

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