Re: [RFC PATCH V3 7/7] mm/slab: place slabobj_ext metadata in unused space within s->size

[Andrey Ryabinin]

On 10/27/25 1:28 PM, Harry Yoo wrote:

>  			slab->obj_exts |= MEMCG_DATA_OBJEXTS;
>  		slab_set_stride(slab, sizeof(struct slabobj_ext));
> +	} else if (obj_exts_in_object(s)) {
> +		unsigned int offset = obj_exts_offset_in_object(s);
> +
> +		slab->obj_exts = (unsigned long)slab_address(slab);
> +		slab->obj_exts += s->red_left_pad;
> +		slab->obj_exts += obj_exts_offset_in_object(s);
> +		if (IS_ENABLED(CONFIG_MEMCG))
> +			slab->obj_exts |= MEMCG_DATA_OBJEXTS;
> +		slab_set_stride(slab, s->size);
> +
> +		for_each_object(addr, s, slab_address(slab), slab->objects) {
> +			kasan_unpoison_range(addr + offset,
> +					     sizeof(struct slabobj_ext));

Is this leftover from previous version? Otherwise I don't get why we unpoison this.

> +			memset(addr + offset, 0, sizeof(struct slabobj_ext));
> +		}
>  	}
>  	metadata_access_disable();
>  }