linux-kernel - Re: [PATCH 1/7] Introduce the pagetable_operations and associated helper macros.

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Date:	Wed, 21 Mar 2007 10:17:40 -0500
From:	Adam Litke <agl@...ibm.com>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	William Lee Irwin III <wli@...omorphy.com>,
	Christoph Hellwig <hch@...radead.org>,
	Ken Chen <kenchen@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/7] Introduce the pagetable_operations and associated
	helper macros.

On Wed, 2007-03-21 at 15:18 +1100, Nick Piggin wrote:
> Adam Litke wrote:
> > Signed-off-by: Adam Litke <agl@...ibm.com>
> > ---
> > 
> >  include/linux/mm.h |   25 +++++++++++++++++++++++++
> >  1 files changed, 25 insertions(+), 0 deletions(-)
> > 
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index 60e0e4a..7089323 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -98,6 +98,7 @@ struct vm_area_struct {
> >  
> >  	/* Function pointers to deal with this struct. */
> >  	struct vm_operations_struct * vm_ops;
> > +	const struct pagetable_operations_struct * pagetable_ops;
> >  
> >  	/* Information about our backing store: */
> >  	unsigned long vm_pgoff;		/* Offset (within vm_file) in PAGE_SIZE
> 
> Can you remind me why this isn't in vm_ops?

We didn't want to bloat the size of the vm_ops struct for all of its
users.

> Also, it is going to be hugepage-only, isn't it? So should the naming be
> changed to reflect that? And #ifdef it...

They are doing some interesting things on Cell that could take advantage
of this.

> > @@ -218,6 +219,30 @@ struct vm_operations_struct {
> >  };
> >  
> >  struct mmu_gather;
> > +
> > +struct pagetable_operations_struct {
> > +	int (*fault)(struct mm_struct *mm,
> > +		struct vm_area_struct *vma,
> > +		unsigned long address, int write_access);
> 
> I got dibs on fault ;)
> 
> My callback is a sanitised one that basically abstracts the details of the
> virtual memory mapping away, so it is usable by drivers and filesystems.
> 
> You actually want to bypass the normal fault handling because it doesn't
> know how to deal with your virtual memory mapping. Hmm, the best suggestion
> I can come up with is handle_mm_fault... unless you can think of a better
> name for me to use.

How about I use handle_pte_fault?

-- 
Adam Litke - (agl at us.ibm.com)
IBM Linux Technology Center

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