Re: [BISECTED] Linux 3.12.7 introduces page map handling regression

[Rik van Riel]

On 01/22/2014 01:24 PM, Linus Torvalds wrote:
> On Wed, Jan 22, 2014 at 10:07 AM, Rik van Riel <riel@xxxxxxxxxx> wrote:
> > The difference between a numa pte and a protnone pte is
> > the VMA permissions.
>
> If that is indeed the only difference, then we should damn well get
> rid of that f*cking stupid _PAGE_NUMA name entirely.
>
> It's misleading crap. Really. Just do a quick grep for that bit, and
> you see just *how* confused people are about it:
>
>     #define _PAGE_NUMA _PAGE_PROTNONE
>     ...
>          if ((pte_flags(a) & (_PAGE_PROTNONE | _PAGE_NUMA)) &
>
> think about it. Just *THINK* about how broken that code is. The whole
> thing is a disaster. _PAGE_NUMA must die. It's shit.

The reason things are this way is that we were
not sure whether we can indeed use _PAGE_PROTNONE
for NUMA balancing on all architectures.

If we are sure that _PAGE_PROTNONE can be used
everywhere, I agree we should get rid of the whole
_PAGE_NUMA naming, and replace that ambiguous
code with some comments and documentation instead.

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