Date: Sat, 20 Mar 2004 12:50:53 -0800
From: William Lee Irwin III <wli@holomorphy.com>
To: Andrew Morton <akpm@osdl.org>
Cc: Andrea Arcangeli <andrea@suse.de>, linux-kernel@vger.kernel.org,
       torvalds@osdl.org
Subject: Re: can device drivers return non-ram via vm_ops->nopage?
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	Andrew Morton <akpm@osdl.org>, Andrea Arcangeli <andrea@suse.de>,
	linux-kernel@vger.kernel.org, torvalds@osdl.org
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On Sat, Mar 20, 2004 at 12:13:45PM -0800, Andrew Morton wrote:
> I agree that ->nopage implementations should not be doing what that driver
> is doing.  ->nopage is defined to return a page*: it's crazy to be
> returning someting from there which isn't covered by mem_map[].
> I just don't think it's important enough to be able to cope with
> non-mem_map[] "memory" in do_no_page(), so I agree that requiring ->mmap()
> to synchronously instantiate the pte's and retaining the debug check in
> do_no_page() is a good idea.

There are other reasons for doing it, e.g. unusual TLB attributes
and/or unusual pagetable structures backing the virtual region. I don't
see anyone standing up and screaming for more functionality than cache
coherency and/or disablement now, so as far as I'm concerned,
remap_area_pages() (or rmk's stuff) kills the issue.


-- wli
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