linux-kernel - Re: [PATCH] mm: Save soft-dirty bits on swapped pages

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Message-ID: <20130724171728.GH8508@moon>
Date:	Wed, 24 Jul 2013 21:17:28 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Matt Mackall <mpm@...enic.com>,
	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCH] mm: Save soft-dirty bits on swapped pages

On Wed, Jul 24, 2013 at 10:06:53AM -0700, Andy Lutomirski wrote:
> > Hi Andy, if I understand you correctly "file-backed pages" are carried
> > in pte with _PAGE_FILE bit set and the swap soft-dirty bit won't be
> > used on them but _PAGE_SOFT_DIRTY will be set on write if only I've
> > not missed something obvious (Pavel?).
> 
> If I understand this stuff correctly, the vmscan code calls
> try_to_unmap when it reclaims memory, which makes its way into
> try_to_unmap_one, which clears the pte (and loses the soft-dirty bit).

Indeed, I was so stareing into swap that forgot about files. I'll do
a separate patch for that, thanks!
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