Subject: Re: [PATCH -V2 3/5] mm: Move change_prot_numa outside CONFIG_ARCH_USES_NUMA_PROT_NONE

From: Rik van Riel <[email-masked]>
Date: Thu, 05 Dec 2013 12:27:34 -0500

On 12/03/2013 10:13 PM, Benjamin Herrenschmidt wrote:
> On Mon, 2013-11-18 at 14:58 +0530, Aneesh Kumar K.V wrote:
>> From: "Aneesh Kumar K.V" <[email-masked]>
>>
>> change_prot_numa should work even if _PAGE_NUMA != _PAGE_PROTNONE.
>> On archs like ppc64 that don't use _PAGE_PROTNONE and also have
>> a separate page table outside linux pagetable, we just need to
>> make sure that when calling change_prot_numa we flush the
>> hardware page table entry so that next page access  result in a numa
>> fault.
>
> That patch doesn't look right...

At first glance, indeed...

> You are essentially making change_prot_numa() do whatever it does (which
> I don't completely understand) *for all architectures* now, whether they
> have CONFIG_ARCH_USES_NUMA_PROT_NONE or not ... So because you want that
> behaviour on powerpc book3s64, you change everybody.

However, it appears that since the code was #ifdefed
like that, the called code was made generic enough,
that change_prot_numa should actually work for
everything.

In other words:

Reviewed-by: Rik van Riel <[email-masked]>