linux-kernel - Re: [PATCH -v6 2/2] Updating ctime and mtime for memory-mapped files

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Date:	Fri, 18 Jan 2008 19:51:43 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	riel@...hat.com
CC:	miklos@...redi.hu, torvalds@...ux-foundation.org,
	peterz@...radead.org, miklos@...redi.hu, salikhmetov@...il.com,
	linux-mm@...ck.org, jakob@...hought.net,
	linux-kernel@...r.kernel.org, valdis.kletnieks@...edu, ksm@...dk,
	staubach@...hat.com, jesper.juhl@...il.com,
	akpm@...ux-foundation.org, protasnb@...il.com,
	r.e.wolff@...wizard.nl, hidave.darkstar@...il.com,
	hch@...radead.org
Subject: Re: [PATCH -v6 2/2] Updating ctime and mtime for memory-mapped
 files

> > > 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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