Re: [PATCH 3/8] mm/zsmalloc: Introduce objcgs pointer in struct zpdesc

[Shakeel Butt <shakeel.butt@linux.dev>]

On Thu, Feb 26, 2026 at 11:29:26AM -0800, Joshua Hahn wrote:
> --- a/mm/zpdesc.h
> +++ b/mm/zpdesc.h
> @@ -20,10 +20,12 @@
>   * @zspage:		Points to the zspage this zpdesc is a part of.
>   * @first_obj_offset:	First object offset in zsmalloc pool.
>   * @_refcount:		The number of references to this zpdesc.
> + * @objcgs:		Array of objcgs pointers that the stored objs
> + *			belong to. Overlayed on top of page->memcg_data, and
> + *			will always have first bit set if it is a valid pointer.
>   *
>   * This struct overlays struct page for now. Do not modify without a good
> - * understanding of the issues. In particular, do not expand into the overlap
> - * with memcg_data.
> + * understanding of the issues.
>   *
>   * Page flags used:
>   * * PG_private identifies the first component page.
> @@ -47,6 +49,9 @@ struct zpdesc {
>  	 */
>  	unsigned int first_obj_offset;
>  	atomic_t _refcount;
> +#ifdef CONFIG_MEMCG
> +	unsigned long objcgs;

Why not just strore struct obj_cgroup ** instead of unsigned long? You will not
need to do conversions when storing or accessing.