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Date: Wed, 7 Mar 2007 01:07:56 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: mingo@elte.hu, npiggin@suse.de, linux-mm@kvack.org,
       linux-kernel@vger.kernel.org, benh@kernel.crashing.org,
       Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [patch 4/6] mm: merge populate and nopage into fault (fixes
 nonlinear)
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On Wed, 07 Mar 2007 09:51:57 +0100 Miklos Szeredi <miklos@szeredi.hu> wrote:

> > > Dirty page accounting doesn't work either on
> > > non-linear mappings
> > 
> > It doesn't?  Confused - these things don't have anything to do with each
> > other do they?
> 
> Look in page_mkclean().  Where does it handle non-linear mappings?
> 

OK, I'd forgotten about that.  It won't break dirty memory accounting,
but it'll potentially break dirty memory balancing.

If we have the wrong page (due to nonlinear), page_check_address() will
fail and we'll leave the pte dirty.  That puts us back to the pre-2.6.17
algorithms and I guess it'll break the msync guarantees.

Peter, I thought we went through the nonlinear problem ages ago and decided
it was OK?