linux-kernel - Re: [PATCH -V8 12/16] hugetlb/cgroup: Add support for cgroup removal

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Message-ID: <20120611085258.GD12402@tiehlicka.suse.cz>
Date:	Mon, 11 Jun 2012 10:52:59 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	linux-mm@...ck.org, kamezawa.hiroyu@...fujitsu.com,
	dhillf@...il.com, rientjes@...gle.com, akpm@...ux-foundation.org,
	hannes@...xchg.org, linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org
Subject: Re: [PATCH -V8 12/16] hugetlb/cgroup: Add support for cgroup removal

On Sat 09-06-12 14:29:57, Aneesh Kumar K.V wrote:
> From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
> 
> This patch add support for cgroup removal. If we don't have parent
> cgroup, the charges are moved to root cgroup.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> ---
>  mm/hugetlb_cgroup.c |   81 +++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 79 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
> index 48efd5a..9458fe3 100644
> --- a/mm/hugetlb_cgroup.c
> +++ b/mm/hugetlb_cgroup.c
> @@ -99,10 +99,87 @@ static void hugetlb_cgroup_destroy(struct cgroup *cgroup)
>  	kfree(h_cgroup);
>  }
>  
> +
> +static int hugetlb_cgroup_move_parent(int idx, struct cgroup *cgroup,
> +				      struct page *page)

deserves a comment about the locking (needs to be called with
hugetlb_lock).

> +{
> +	int csize;
> +	struct res_counter *counter;
> +	struct res_counter *fail_res;
> +	struct hugetlb_cgroup *page_hcg;
> +	struct hugetlb_cgroup *h_cg   = hugetlb_cgroup_from_cgroup(cgroup);
> +	struct hugetlb_cgroup *parent = parent_hugetlb_cgroup(cgroup);
> +
> +	if (!get_page_unless_zero(page))
> +		goto out;
> +
> +	page_hcg = hugetlb_cgroup_from_page(page);
> +	/*
> +	 * We can have pages in active list without any cgroup
> +	 * ie, hugepage with less than 3 pages. We can safely
> +	 * ignore those pages.
> +	 */
> +	if (!page_hcg || page_hcg != h_cg)
> +		goto err_out;

How can we have page_hcg != NULL && page_hcg != h_cg?

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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