linux-kernel - Re: [PATCH 0/2] Updating ctime and mtime for memory-mapped files [try #4]

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Date:	Tue, 15 Jan 2008 21:40:47 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	a.p.zijlstra@...llo.nl
CC:	miklos@...redi.hu, salikhmetov@...il.com, linux-mm@...ck.org,
	jakob@...hought.net, linux-kernel@...r.kernel.org,
	valdis.kletnieks@...edu, riel@...hat.com, ksm@...dk,
	staubach@...hat.com, jesper.juhl@...il.com,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	protasnb@...il.com
Subject: Re: [PATCH 0/2] Updating ctime and mtime for memory-mapped files
	[try #4]

> On Tue, 2008-01-15 at 21:27 +0100, Miklos Szeredi wrote:
> > > 1. Introduction
> > > 
> > > This is the fourth version of my solution for the bug #2645:
> > > 
> > > http://bugzilla.kernel.org/show_bug.cgi?id=2645
> > > 
> > > Changes since the previous version:
> > > 
> > > 1) the case of retouching an already-dirty page pointed out
> > >   by Miklos Szeredi has been addressed;
> > 
> > I'm a bit sceptical, as we've also pointed out, that this is not
> > possible without messing with the page tables.
> > 
> > Did you try my test program on the patched kernel?
> > 
> > I've refreshed the patch, where we left this issue last time.  It
> > should basically have equivalent functionality to your patch, and is a
> > lot simpler.  There might be performance issues with it, but it's a
> > good starting point.
> 
> It has the same problem as Anton's in that it won't get triggered again
> for an already dirty mapped page.

Yes, it's not better in this respect, than Anton's patch.  And it
might be worse performance-wise, since file_update_time() is sure to
be slower, than set_bit().  According to Andrew, this may not actually
matter in practice, but that would have to be benchmarked, I guess.

Miklos
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