Date: Wed, 24 Jul 2013 22:52:56 +0400
From: Cyrill Gorcunov <gorcunov@gmail.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: James Bottomley <James.Bottomley@hansenpartnership.com>,
        Linux MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>,
        Pavel Emelyanov <xemul@parallels.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Matt Mackall <mpm@selenic.com>,
        Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>,
        Marcelo Tosatti <mtosatti@redhat.com>,
        KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>
Subject: Re: [PATCH] mm: Save soft-dirty bits on swapped pages
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On Wed, Jul 24, 2013 at 11:21:46AM -0700, Andy Lutomirski wrote:
> >
> > I fear for tracking soft-dirty-bit for swapped entries we sinply have
> > no other place than pte (still i'm quite open for ideas, maybe there
> > are a better way which I've missed).
> 
> I know approximately nothing about how swap and anon_vma work.
> 
> For files, sticking it in struct page seems potentially nicer,
> although finding a free bit might be tough.  (FWIW, I have plans to
> free up a page flag on x86 some time moderately soon as part of a
> completely unrelated project.)  I think this stuff really belongs to
> the address_space more than it belongs to the pte.

Well, some part of information already lays in pte (such as 'file' bit,
swap entries) so it looks natural i think to work on this level. but
letme think if use page struct for that be more convenient...

> 
> How do you handle the write syscall?

I fear I somehow miss your point here, could please alaborate a bit?
There is no additional code I know of being write() specific, just
a code for #PF exceptions.
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