linux-kernel - Re: vm_ops.page_mkwrite() fails with vmalloc on 2.6.23

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Message-Id: <1193749958.27652.77.camel@twins>
Date:	Tue, 30 Oct 2007 14:12:38 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	Stefani Seibold <stefani@...bold.net>,
	Jaya Kumar <jayakumar.lkml@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, David Howells <dhowells@...hat.com>,
	linux-mm@...ck.org
Subject: Re: vm_ops.page_mkwrite() fails with vmalloc on 2.6.23

On Tue, 2007-10-30 at 12:39 +0000, Hugh Dickins wrote:
> On Tue, 30 Oct 2007, Stefani Seibold wrote:
> > 
> > the question is how can i get all pte's from a vmalloc'ed memory. Due to
> > the zeroed mapping pointer i dont see how to do this?
> 
> The mapping pointer is zeroed because you've done nothing to set it.
> Below is how I answered you a week ago.  But this is new territory
> (extending page_mkclean to work on more than just pagecache pages),
> I'm still unsure what would be the safest way to do it.

Quite, I think manual usage of page_mkclean_one() on the vma gotten from
mmap() along with properly setting page->index is the simplest solution
to make work.

Making page_mkclean(struct page *) work for remap_pfn/vmalloc_range()
style mmaps would require extending rmap to work with those, which
includes setting page->mapping to point to a anon_vma like object.

But that sounds like a lot of work, and I'm not sure its worth the
overhead, because so far all users of remap_pfn/vmalloc_range() have
survived without.

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