linux-kernel - Re: [PATCH 09/18] mm: numa: Clear numa hinting information on mprotect

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Date:	Mon, 09 Dec 2013 10:57:47 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Mel Gorman <mgorman@...e.de>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Alex Thorlton <athorlton@....com>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 09/18] mm: numa: Clear numa hinting information on mprotect

On 12/09/2013 02:09 AM, Mel Gorman wrote:
> On a protection change it is no longer clear if the page should be still
> accessible.  This patch clears the NUMA hinting fault bits on a protection
> change.

I had to think about this one, because my first thought was
"wait, aren't NUMA ptes inaccessible already?".

Then I thought about doing things like adding read or write
permission in the mprotect, eg. changing from PROT_NONE to
PROT_READ ... and it became unclear what to do with the NUMA
bit in that case...

This patch clears up some confusing situations :)

> Cc: stable@...r.kernel.org
> Signed-off-by: Mel Gorman <mgorman@...e.de>

Reviewed-by: Rik van Riel <riel@...hat.com>

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