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Date: Wed, 22 Oct 2014 12:49:30 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Dominik Dingel <dingel@linux.vnet.ibm.com>
Cc: linux-mm@kvack.org, Mel Gorman <mgorman@suse.de>,
        Michal Hocko <mhocko@suse.cz>, Paolo Bonzini <pbonzini@redhat.com>,
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        Martin Schwidefsky <schwidefsky@de.ibm.com>,
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        Sasha Levin <sasha.levin@oracle.com>
Subject: Re: [PATCH 2/4] mm: introduce mm_forbids_zeropage function
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On Wed, 22 Oct 2014 21:45:52 +0200 Dominik Dingel <dingel@linux.vnet.ibm.com> wrote:

> > > +#ifndef mm_forbids_zeropage
> > > +#define mm_forbids_zeropage(X)  (0)
> > > +#endif
> > 
> > Can we document this please?  What it does, why it does it.  We should
> > also specify precisely which arch header file is responsible for
> > defining mm_forbids_zeropage.
> > 
> 
> I will add a comment like:
> 
> /*
>  * To prevent common memory management code establishing
>  * a zero page mapping on a read fault.
>  * This function should be implemented within <asm/pgtable.h>.

s/function should be implemented/macro should be defined/

>  * s390 does this to prevent multiplexing of hardware bits
>  * related to the physical page in case of virtualization.
>  */
> 
> Okay?

Looks great, thanks.