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From: Daniel Phillips <phillips@bonn-fries.net>
To: Russell King <rmk@arm.linux.org.uk>, linux-kernel@vger.kernel.org
Subject: Re: Bug: Discontigmem virt_to_page() [Alpha,ARM,Mips64?]
Date: Sun, 28 Apr 2002 00:10:20 +0200
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On Friday 26 April 2002 20:27, Russell King wrote:
> Hi,
> 
> I've been looking at some of the ARM discontigmem implementations, and
> have come across a nasty bug.  To illustrate this, I'm going to take
> part of the generic kernel, and use the Alpha implementation to
> illustrate the problem we're facing on ARM.
> 
> I'm going to argue here that virt_to_page() can, in the discontigmem
> case, produce rather a nasty bug when used with non-direct mapped
> kernel memory arguments.

It's tough to follow, even when you know the code.  While cooking my
config_nonlinear patch I noticed the line you're concerned about and
regarded it with deep suspicion.  My patch does this:

-               page = virt_to_page(__va(phys_addr));
+               page = phys_to_page(phys_addr);

And of course took care that phys_to_page does the right thing in all
cases.

<plug>
The new config_nonlinear was designed as a cleaner, more powerful
replacement for all non-numa uses of config_discontigmem.
</plug>

-- 
Daniel
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