linux-kernel - Re: [PATCH] mm: avoid dirtying shared mappings on mlock

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Message-Id: <200710122223.02061.nickpiggin@yahoo.com.au>
Date:	Fri, 12 Oct 2007 22:23:01 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Suleiman Souhlal <ssouhlal@...ebsd.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Suleiman Souhlal <suleiman@...gle.com>,
	linux-mm <linux-mm@...ck.org>, hugh <hugh@...itas.com>
Subject: Re: [PATCH] mm: avoid dirtying shared mappings on mlock

On Friday 12 October 2007 20:50, Peter Zijlstra wrote:
> On Fri, 2007-10-12 at 04:14 +1000, Nick Piggin wrote:
> > On Friday 12 October 2007 20:37, Peter Zijlstra wrote:

> > > The pages will still be read-only due to dirty tracking, so the first
> > > write will still do page_mkwrite().
> >
> > Which can SIGBUS, no?
>
> Sure, but that is no different than any other mmap'ed write. I'm not
> seeing how an mlocked region is special here.

Well it is a change in behaviour (admittedly, so was the change
to SIGBUS mmaped writes in the first place). It's a matter of
semantics I guess. Is the current behaviour actually a _problem_
for anyone? If not, then do we need to change it?

I'm not saying it does matter, just that it might matter ;)
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