To: riel@redhat.com
CC: miklos@szeredi.hu, torvalds@linux-foundation.org, peterz@infradead.org,
       miklos@szeredi.hu, salikhmetov@gmail.com, linux-mm@kvack.org,
       jakob@unthought.net, linux-kernel@vger.kernel.org,
       valdis.kletnieks@vt.edu, ksm@42.dk, staubach@redhat.com,
       jesper.juhl@gmail.com, akpm@linux-foundation.org, protasnb@gmail.com,
       r.e.wolff@bitwizard.nl, hidave.darkstar@gmail.com, hch@infradead.org
In-reply-to: <20080118132850.044537e5@bree.surriel.com> (message from Rik van
	Riel on Fri, 18 Jan 2008 13:28:50 -0500)
Subject: Re: [PATCH -v6 2/2] Updating ctime and mtime for memory-mapped
 files
References: <12006091182260-git-send-email-salikhmetov@gmail.com>
	<12006091211208-git-send-email-salikhmetov@gmail.com>
	<E1JFnsg-0008UU-LU@pomaz-ex.szeredi.hu>
	<1200651337.5920.9.camel@twins>
	<1200651958.5920.12.camel@twins>
	<alpine.LFD.1.00.0801180949040.2957@woody.linux-foundation.org>
	<E1JFvgx-0000zz-2C@pomaz-ex.szeredi.hu> <20080118132850.044537e5@bree.surriel.com>
Message-Id: <E1JFwJb-00018k-I1@pomaz-ex.szeredi.hu>
From: Miklos Szeredi <miklos@szeredi.hu>
Date: Fri, 18 Jan 2008 19:51:43 +0100
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1037
Lines: 29

> > > And even in that four-liner, I suspect that the *last* two lines are 
> > > actually incorrect: there's no point in updating the file time when the 
> > > page *becomes* dirty,
> > 
> > Actually all four lines do that.  The first two for a write access on
> > a present, read-only pte, the other two for a write on a non-present
> > pte.
> > 
> > > we should update the file time when it is marked 
> > > clean, and "msync(MS_SYNC)" should update it as part of *that*.
> > 
> > That would need a new page flag (PG_mmap_dirty?).  Do we have one
> > available?
> 
> I thought the page writing stuff looked at (and cleared) the pte
> dirty bit, too?

Yeah, it does.  Hmm...

What happens on munmap?  The times _could_ get updated from there as
well, but it's getting complicated.

Miklos

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