Re: [PATCH] mm/slab: fix folio_test_{anon,ksm}() false positive on slabs

[Harry Yoo <harry.yoo@oracle.com>]

On Mon, Jun 09, 2025 at 09:06:04AM -0700, Christoph Lameter (Ampere) wrote:
> On Mon, 9 Jun 2025, Harry Yoo wrote:
> 
> >   [ field ]		[ offset ] [ size ]
> >   page->mapping		24         8
> >   page->lru		8	   16
> >
> >   slab->next		16	   8
> >   slab->slabs		24	   4
> >
> > Reorder ->slabs and ->next, so that the layout will be:
> >
> >   slab->slabs		16	   4
> >   slab->next		24	   8
> >
> > After reordering, slab->slabs shares its offset with page->lru.prev,
> > which is not a problem. slab->next now shares the offset with
> > page->mapping, but that's fine, as a slab is double-word aligned.
> 
> Add comments to document the trickery that is going on here? Otherwise we
> may stumble across this issue again later.

Will add, thanks!

-- 
Cheers,
Harry / Hyeonggon