Re: [PATCH v4 23/32] mm/memcg: Convert slab objcgs from struct page to struct slab

[Roman Gushchin <guro-b10kYP2dOMg@public.gmane.org>]

On Tue, Jan 04, 2022 at 01:10:37AM +0100, Vlastimil Babka wrote:
> page->memcg_data is used with MEMCG_DATA_OBJCGS flag only for slab pages
> so convert all the related infrastructure to struct slab. Also use
> struct folio instead of struct page when resolving object pointers.
> 
> This is not just mechanistic changing of types and names. Now in
> mem_cgroup_from_obj() we use folio_test_slab() to decide if we interpret
> the folio as a real slab instead of a large kmalloc, instead of relying
> on MEMCG_DATA_OBJCGS bit that used to be checked in page_objcgs_check().
> Similarly in memcg_slab_free_hook() where we can encounter
> kmalloc_large() pages (here the folio slab flag check is implied by
> virt_to_slab()). As a result, page_objcgs_check() can be dropped instead
> of converted.

Btw, it seems that with some minimal changes we can drop the whole thing
with the changing of the lower bit and rely on the slab page flag.
I'll prepare a patch on top of your series.

Thanks!