Re: [PATCH 5/6] mm/hugetlb: fix sysfs group leak in hugetlb_unregister_node()

["Yin, Fengwei" <fengwei.yin@intel.com>]

On 8/16/2022 9:05 PM, Miaohe Lin wrote:
> The sysfs group per_node_hstate_attr_group and hstate_demote_attr_group
> when h->demote_order != 0 are created in hugetlb_register_node(). But
> these sysfs groups are not removed when unregister the node, thus sysfs
> group is leaked. Using sysfs_remove_group() to fix this issue.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Fengwei Yin <fengwei.yin@intel.com>

Regards
Yin, Fengwei

> ---
>  mm/hugetlb.c | 25 ++++++++++++++++++-------
>  1 file changed, 18 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index b69d7808f457..e1356ad57087 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3850,12 +3850,18 @@ static int hugetlb_sysfs_add_hstate(struct hstate *h, struct kobject *parent,
>  	}
>  
>  	if (h->demote_order) {
> -		if (sysfs_create_group(hstate_kobjs[hi],
> -					&hstate_demote_attr_group))
> +		retval = sysfs_create_group(hstate_kobjs[hi],
> +					    &hstate_demote_attr_group);
> +		if (retval) {
>  			pr_warn("HugeTLB unable to create demote interfaces for %s\n", h->name);
> +			sysfs_remove_group(hstate_kobjs[hi], hstate_attr_group);
> +			kobject_put(hstate_kobjs[hi]);
> +			hstate_kobjs[hi] = NULL;
> +			return retval;
> +		}
>  	}
>  
> -	return retval;
> +	return 0;
>  }
>  
>  static void __init hugetlb_sysfs_init(void)
> @@ -3941,10 +3947,15 @@ static void hugetlb_unregister_node(struct node *node)
>  
>  	for_each_hstate(h) {
>  		int idx = hstate_index(h);
> -		if (nhs->hstate_kobjs[idx]) {
> -			kobject_put(nhs->hstate_kobjs[idx]);
> -			nhs->hstate_kobjs[idx] = NULL;
> -		}
> +		struct kobject *hstate_kobj = nhs->hstate_kobjs[idx];
> +
> +		if (!hstate_kobj)
> +			continue;
> +		if (h->demote_order)
> +			sysfs_remove_group(hstate_kobj, &hstate_demote_attr_group);
> +		sysfs_remove_group(hstate_kobj, &per_node_hstate_attr_group);
> +		kobject_put(hstate_kobj);
> +		nhs->hstate_kobjs[idx] = NULL;
>  	}
>  
>  	kobject_put(nhs->hugepages_kobj);