Re: [PATCH -V9 12/15] hugetlb/cgroup: Add support for cgroup removal

[Michal Hocko <mhocko@suse.cz>]

On Wed 13-06-12 15:57:31, Aneesh Kumar K.V wrote:
> From: "Aneesh Kumar K.V" <aneesh.kumar@linux.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@linux.vnet.ibm.com>

Reviewed-by: Michal Hocko <mhocko@suse.cz>

> ---
>  mm/hugetlb_cgroup.c |   70 +++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 68 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
> index 0f2f6ac..a3a68a4 100644
> --- a/mm/hugetlb_cgroup.c
> +++ b/mm/hugetlb_cgroup.c
> @@ -107,10 +107,76 @@ static void hugetlb_cgroup_destroy(struct cgroup *cgroup)
>  	kfree(h_cgroup);
>  }
>  
> +
> +/*
> + * Should be called with hugetlb_lock held.
> + * Since we are holding hugetlb_lock, pages cannot get moved from
> + * active list or uncharged from the cgroup, So no need to get
> + * page reference and test for page active here. This function
> + * cannot fail.
> + */
> +static void hugetlb_cgroup_move_parent(int idx, struct cgroup *cgroup,
> +				       struct page *page)
> +{
> +	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);
> +
> +	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 out;
> +
> +	csize = PAGE_SIZE << compound_order(page);
> +	if (!parent) {
> +		parent = root_h_cgroup;
> +		/* root has no limit */
> +		res_counter_charge_nofail(&parent->hugepage[idx],
> +					  csize, &fail_res);
> +	}
> +	counter = &h_cg->hugepage[idx];
> +	res_counter_uncharge_until(counter, counter->parent, csize);
> +
> +	set_hugetlb_cgroup(page, parent);
> +out:
> +	return;
> +}
> +
> +/*
> + * Force the hugetlb cgroup to empty the hugetlb resources by moving them to
> + * the parent cgroup.
> + */
>  static int hugetlb_cgroup_pre_destroy(struct cgroup *cgroup)
>  {
> -	/* We will add the cgroup removal support in later patches */
> -	   return -EBUSY;
> +	struct hstate *h;
> +	struct page *page;
> +	int ret = 0, idx = 0;
> +
> +	do {
> +		if (cgroup_task_count(cgroup) ||
> +		    !list_empty(&cgroup->children)) {
> +			ret = -EBUSY;
> +			goto out;
> +		}
> +		for_each_hstate(h) {
> +			spin_lock(&hugetlb_lock);
> +			list_for_each_entry(page, &h->hugepage_activelist, lru)
> +				hugetlb_cgroup_move_parent(idx, cgroup, page);
> +
> +			spin_unlock(&hugetlb_lock);
> +			idx++;
> +		}
> +		cond_resched();
> +	} while (hugetlb_cgroup_have_usage(cgroup));
> +out:
> +	return ret;
>  }
>  
>  int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
> -- 
> 1.7.10
> 

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