Re: Bug: Discontigmem virt_to_page() [Alpha,ARM,Mips64?]

Daniel Phillips
2002-04-28T22:10:09Z

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