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Date: Wed, 27 May 2015 10:33:43 -0400
From: Jerome Glisse <j.glisse@gmail.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, Linus Torvalds <torvalds@linux-foundation.org>,
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        =?iso-8859-1?B?Suly9G1l?= Glisse <jglisse@redhat.com>
Subject: Re: [PATCH 03/36] mmu_notifier: pass page pointer to
 mmu_notifier_invalidate_page()
Message-ID: <20150527143342.GB1948@gmail.com>
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On Wed, May 27, 2015 at 10:47:44AM +0530, Aneesh Kumar K.V wrote:
> j.glisse@gmail.com writes:
> 
> > From: Jérôme Glisse <jglisse@redhat.com>
> >
> > Listener of mm event might not have easy way to get the struct page
> > behind and address invalidated with mmu_notifier_invalidate_page()
> > function as this happens after the cpu page table have been clear/
> > updated. This happens for instance if the listener is storing a dma
> > mapping inside its secondary page table. To avoid complex reverse
> > dma mapping lookup just pass along a pointer to the page being
> > invalidated.
> 
> .....
> 
> > diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
> > index ada3ed1..283ad26 100644
> > --- a/include/linux/mmu_notifier.h
> > +++ b/include/linux/mmu_notifier.h
> > @@ -172,6 +172,7 @@ struct mmu_notifier_ops {
> >  	void (*invalidate_page)(struct mmu_notifier *mn,
> >  				struct mm_struct *mm,
> >  				unsigned long address,
> > +				struct page *page,
> >  				enum mmu_event event);
> >  
> 
> How do we handle this w.r.t invalidate_range ? 

With range invalidation the CPU page table is still reliable when
invalidate_range_start() callback happen. So we can lookup the CPU
page table to get the page backing the address.

Cheers,
Jérôme