Re: [PATCH v2 1/1] mm/vmscan.c: Prevent allocating shrinker_info on offlined nodes

[Matthew Wilcox]

On Tue, Dec 07, 2021 at 05:40:13PM -0500, Nico Pache wrote:
> +++ b/mm/vmscan.c
> @@ -222,13 +222,16 @@ static int expand_one_shrinker_info(struct mem_cgroup *memcg,
>  	int size = map_size + defer_size;
>  
>  	for_each_node(nid) {
> +		int tmp = nid;
>  		pn = memcg->nodeinfo[nid];
>  		old = shrinker_info_protected(memcg, nid);
>  		/* Not yet online memcg */
>  		if (!old)
>  			return 0;
>  
> -		new = kvmalloc_node(sizeof(*new) + size, GFP_KERNEL, nid);
> +		if(!node_online(nid))
> +			tmp = numa_mem_id();
> +		new = kvmalloc_node(sizeof(*new) + size, GFP_KERNEL, tmp);
>  		if (!new)

Why should this be fixed here and not in, say, kvmalloc_node()?