linux-kernel - Re: [patch 3/6] mmu_notifier: invalidate

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Date:	Tue, 19 Feb 2008 14:30:09 +0100
From:	Andrea Arcangeli <andrea@...ranet.com>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Christoph Lameter <clameter@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Robin Holt <holt@....com>, Avi Kivity <avi@...ranet.com>,
	Izik Eidus <izike@...ranet.com>,
	kvm-devel@...ts.sourceforge.net,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	general@...ts.openfabrics.org,
	Steve Wise <swise@...ngridcomputing.com>,
	Roland Dreier <rdreier@...co.com>,
	Kanoj Sarcar <kanojsarcar@...oo.com>, steiner@....com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	daniel.blueman@...drics.com
Subject: Re: [patch 3/6] mmu_notifier: invalidate_page callbacks

On Tue, Feb 19, 2008 at 07:46:10PM +1100, Nick Piggin wrote:
> On Sunday 17 February 2008 06:22, Christoph Lameter wrote:
> > On Fri, 15 Feb 2008, Andrew Morton wrote:
> 
> > > >  		flush_cache_page(vma, address, pte_pfn(*pte));
> > > >  		entry = ptep_clear_flush(vma, address, pte);
> > > > +		mmu_notifier(invalidate_page, mm, address);
> > >
> > > I just don't see how ths can be done if the callee has another thread in
> > > the middle of establishing IO against this region of memory.
> > > ->invalidate_page() _has_ to be able to block.  Confused.
> >
> > The page lock is held and that holds off I/O?
> 
> I think the actual answer is that "it doesn't matter".

Agreed. The PG_lock itself taken when invalidate_page is called, is
used to serialized the VM against the VM, not the VM against I/O.
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