linux-kernel - Re: [PATCH RFC] mm/hugetlb_cgroup: Add huge_page_order check to avoid incorrectly uncharge

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Date:	Tue, 10 Jul 2012 23:11:07 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Wanpeng Li <liwp.linux@...il.com>, linux-mm@...ck.org
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Li Zefan <lizefan@...wei.com>, Tejun Heo <tj@...nel.org>,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	Wanpeng Li <liwp.linux@...il.com>
Subject: Re: [PATCH RFC] mm/hugetlb_cgroup: Add huge_page_order check to avoid incorrectly uncharge

Wanpeng Li <liwp.linux@...il.com> writes:

> From: Wanpeng Li <liwp@...ux.vnet.ibm.com>
>
> Against linux-next:
>
> Function alloc_huge_page will call hugetlb_cgroup_charge_cgroup
> to charge pages, the compound page have less than 3 pages will not
> charge to hugetlb cgroup. When alloc_huge_page fails it will call
> hugetlb_cgroup_uncharge_cgroup to uncharge pages, however,
> hugetlb_cgroup_uncharge_cgroup doesn't have huge_page_order check.
> That means it will uncharge pages even if the compound page have less
> than 3 pages. Add huge_page_order check to avoid this incorrectly
> uncharge.
>
> Signed-off-by: Wanpeng Li <liwp.linux@...il.com>

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



> ---
>  mm/hugetlb_cgroup.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
> index b834e8d..2b9e214 100644
> --- a/mm/hugetlb_cgroup.c
> +++ b/mm/hugetlb_cgroup.c
> @@ -252,6 +252,9 @@ void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
>
>  	if (hugetlb_cgroup_disabled() || !h_cg)
>  		return;
> +
> +	if (huge_page_order(&hstates[idx]) < HUGETLB_CGROUP_MIN_ORDER)
> +		return;
>
>  	res_counter_uncharge(&h_cg->hugepage[idx], csize);
>  	return;
> -- 
> 1.7.5.4

-aneesh

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