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

[Harry Yoo]

On Wed, Oct 29, 2025 at 07:19:29PM +0100, Andrey Ryabinin wrote:
> 
> 
> 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.

Oh god, yes! Thanks for catching. Will fix in the next version.

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

-- 
Cheers,
Harry / Hyeonggon