linux-kernel - Re: [PATCH v8 2/3] mm/mempolicy: Prepare weighted interleave sysfs for memory hotplug

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Message-ID: <68003826cb17d_1302d294e@dwillia2-xfh.jf.intel.com.notmuch>
Date: Wed, 16 Apr 2025 16:07:18 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: Rakie Kim <rakie.kim@...com>, <akpm@...ux-foundation.org>
CC: <gourry@...rry.net>, <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
	<linux-cxl@...r.kernel.org>, <joshua.hahnjy@...il.com>,
	<dan.j.williams@...el.com>, <ying.huang@...ux.alibaba.com>,
	<david@...hat.com>, <Jonathan.Cameron@...wei.com>, <osalvador@...e.de>,
	<kernel_team@...ynix.com>, <honggyu.kim@...com>, <yunjeong.mun@...com>,
	<rakie.kim@...com>
Subject: Re: [PATCH v8 2/3] mm/mempolicy: Prepare weighted interleave sysfs
 for memory hotplug

Rakie Kim wrote:
> Previously, the weighted interleave sysfs structure was statically
> managed during initialization. This prevented new nodes from being
> recognized when memory hotplug events occurred, limiting the ability
> to update or extend sysfs entries dynamically at runtime.
> 
> To address this, this patch refactors the sysfs infrastructure and
> encapsulates it within a new structure, `sysfs_wi_group`, which holds
> both the kobject and an array of node attribute pointers.
> 
> By allocating this group structure globally, the per-node sysfs
> attributes can be managed beyond initialization time, enabling
> external modules to insert or remove node entries in response to
> events such as memory hotplug or node online/offline transitions.
> 
> Instead of allocating all per-node sysfs attributes at once, the
> initialization path now uses the existing sysfs_wi_node_add() and
> sysfs_wi_node_delete() helpers. This refactoring makes it possible
> to modularly manage per-node sysfs entries and ensures the
> infrastructure is ready for runtime extension.
> 
> Signed-off-by: Rakie Kim <rakie.kim@...com>
> Reviewed-by: Gregory Price <gourry@...rry.net>
> Reviewed-by: Joshua Hahn <joshua.hahnjy@...il.com>
> ---
>  mm/mempolicy.c | 60 ++++++++++++++++++++++++--------------------------
>  1 file changed, 29 insertions(+), 31 deletions(-)
> 
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index dcf03c389b51..998635127e9d 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -3419,6 +3419,13 @@ struct iw_node_attr {
>  	int nid;
>  };
>  
> +struct sysfs_wi_group {
> +	struct kobject wi_kobj;
> +	struct iw_node_attr *nattrs[];
> +};
> +
> +static struct sysfs_wi_group *wi_group;
> +
>  static ssize_t node_show(struct kobject *kobj, struct kobj_attribute *attr,
>  			 char *buf)
>  {
> @@ -3461,24 +3468,23 @@ static ssize_t node_store(struct kobject *kobj, struct kobj_attribute *attr,
>  	return count;
>  }
>  
> -static struct iw_node_attr **node_attrs;
> -
> -static void sysfs_wi_node_delete(struct iw_node_attr *node_attr,
> -				 struct kobject *parent)
> +static void sysfs_wi_node_delete(int nid)
>  {
> -	if (!node_attr)
> +	if (!wi_group->nattrs[nid])
>  		return;
> -	sysfs_remove_file(parent, &node_attr->kobj_attr.attr);
> -	kfree(node_attr->kobj_attr.attr.name);
> -	kfree(node_attr);
> +
> +	sysfs_remove_file(&wi_group->wi_kobj,
> +			  &wi_group->nattrs[nid]->kobj_attr.attr);
> +	kfree(wi_group->nattrs[nid]->kobj_attr.attr.name);
> +	kfree(wi_group->nattrs[nid]);
>  }
>  
> -static void sysfs_wi_node_delete_all(struct kobject *wi_kobj)
> +static void sysfs_wi_node_delete_all(void)
>  {
>  	int nid;
>  
>  	for (nid = 0; nid < nr_node_ids; nid++)
> -		sysfs_wi_node_delete(node_attrs[nid], wi_kobj);
> +		sysfs_wi_node_delete(nid);
>  }
>  
>  static void iw_table_free(void)
> @@ -3501,8 +3507,7 @@ static void iw_table_free(void)
>  static void wi_kobj_release(struct kobject *wi_kobj)
>  {
>  	iw_table_free();
> -	kfree(node_attrs);
> -	kfree(wi_kobj);
> +	kfree(wi_group);

Ah, look just one more iw_table_free() deletion to be able to switch to
kobject_create_and_add() flow.

For what this patch is though you can add:

Reviewed-by: Dan Williams <dan.j.williams@...el.com>