Re: [PATCH v2 31/33] mm/sl*b: Differentiate struct slab fields by sl*b implementations

[Matthew Wilcox <willy@xxxxxxxxxxxxx>]

On Fri, Dec 10, 2021 at 07:26:11PM +0100, Vlastimil Babka wrote:
> > Because SLUB and SLAB sets slab->slab_cache = NULL (to set page->mapping = NULL),
> 
> Hm, now that you mention it, maybe it would be better to do a
> "folio->mapping = NULL" instead as we now have a more clearer view where we
> operate on struct slab, and where we transition between that and a plain
> folio. This is IMHO part of preparing the folio for freeing, not a struct
> slab cleanup as struct slab doesn't need this cleanup.

Yes, I did that as part of "mm/slub: Convert slab freeing to struct slab"
in my original series:

-       __ClearPageSlabPfmemalloc(page);
+       __slab_clear_pfmemalloc(slab);
        __ClearPageSlab(page);
-       /* In union with page->mapping where page allocator expects NULL */
-       page->slab_cache = NULL;
+       page->mapping = NULL;