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

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Date:	Wed, 21 Mar 2007 16:07:43 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	William Lee Irwin III <wli@...omorphy.com>
CC:	Adam Litke <agl@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	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.

William Lee Irwin III wrote:
> Adam Litke wrote:
> 
>>> 	struct vm_operations_struct * vm_ops;
>>>+	const struct pagetable_operations_struct * pagetable_ops;
> 
> 
> On Wed, Mar 21, 2007 at 03:18:30PM +1100, Nick Piggin wrote:
> 
>>Can you remind me why this isn't in vm_ops?
>>Also, it is going to be hugepage-only, isn't it? So should the naming be
>>changed to reflect that? And #ifdef it...
> 
> 
> ISTR potential ppc64 users coming out of the woodwork for something I
> didn't recognize the name of, but I may be confusing that with your
> patch. I can implement additional users (and useful ones at that)
> needing this in particular if desired.

Yes I would be interested in seeing useful additional users of this
that cannot use our regular virtual memory, before making it a general
thing.

I just don't want to see proliferation of these things, if possible.

> Adam Litke wrote:
> 
>>>+struct pagetable_operations_struct {
>>>+	int (*fault)(struct mm_struct *mm,
> 
> 
> On Wed, Mar 21, 2007 at 03:18:30PM +1100, Nick Piggin wrote:
> 
>>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.
> 
> 
> Two fault handling methods callbacks raise an eyebrow over here at least.
> I was vaguely hoping for unification of the fault handling callbacks.

I don't know if it would be so clean to do that as they are at different levels.
Adam's fault is before the VM translation (and bypasses it), and mine is after.

-- 
SUSE Labs, Novell Inc.
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