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

[Aneesh Kumar K.V]

Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> 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@xxxxxxxxxxxxxxxxxx>


>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
>
> 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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