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

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Message-ID: <87fwa25gqj.fsf@skywalker.in.ibm.com>
Date:	Mon, 11 Jun 2012 15:10:20 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Michal Hocko <mhocko@...e.cz>
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

Michal Hocko <mhocko@...e.cz> writes:

> 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).

will do

>
>> +{
>> +	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?

pages belonging to other cgroup ?

-aneesh

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