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Date: Sun, 18 Jun 2006 12:11:43 +0200
From: Nick Piggin <npiggin@suse.de>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@osdl.org>,
       Christoph Lameter <clameter@engr.sgi.com>, Jens Axboe <axboe@suse.de>,
       Linux Memory Management List <linux-mm@kvack.org>
Subject: Re: [patch] rfc: fix splice mapping race?
Message-ID: <20060618101143.GE14452@wotan.suse.de>
References: <20060618094157.GD14452@wotan.suse.de> <1150624965.28517.55.camel@lappy>
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On Sun, Jun 18, 2006 at 12:02:45PM +0200, Peter Zijlstra wrote:
> > In page migration, detect the missing mapping early and bail out if
> > that is the case: the page is not going to get un-truncated, so
> > retrying is just a waste of time.
> > 
> > Signed-off-by: Nick Piggin <npiggin@suse.de>
> 
> Looks sane, except the change in migrate (comment there). I like the
> remove_mapping() pre-conditions.

Thanks.

> > --- linux-2.6.orig/mm/migrate.c
> > +++ linux-2.6/mm/migrate.c
> > @@ -136,9 +136,13 @@ static int swap_page(struct page *page)
> >  {
> >  	struct address_space *mapping = page_mapping(page);
> >  
> > -	if (page_mapped(page) && mapping)
> > +	if (!mapping)
> > +		return -EINVAL; /* page truncated. signal permanent failure */
> 
> Here, I think you need to unlock the page too.

Bah, yes thanks... I'll post an updated patch after others have
had time to comment.

Nick