Re: [PATCH v9 09/12] mm/kasan: kasan specific map populate function

[Michal Hocko]

On Mon 09-10-17 13:51:47, Pavel Tatashin wrote:
> Hi Will,
> 
> I can go back to that approach, if Michal OK with it. But, that would
> mean that I would need to touch every single architecture that
> implements vmemmap_populate(), and also pass flags at least through
> these functions on every architectures (some have more than one
> decided by configs).:
> 
> vmemmap_populate()
> vmemmap_populate_basepages()
> vmemmap_populate_hugepages()
> vmemmap_pte_populate()
> __vmemmap_alloc_block_buf()
> alloc_block_buf()
> vmemmap_alloc_block()
> 
> IMO, while I understand that it looks strange that we must walk page
> table after creating it, it is a better approach: more enclosed as it
> effects kasan only, and more universal as it is in common code.

While I understand that gfp mask approach might look better at first
sight this is by no means a general purpose API so I would rather be
pragmatic and have a smaller code footprint than a more general
interface. Kasan is pretty much a special case and doing a one time
initialization 2 pass thing is imho acceptable. If this turns out to be
impractical in future then let's fix it up but right now I would rather
go a simpler path.
-- 
Michal Hocko
SUSE Labs