Re: ioremap_nocache problem?

[Jeff Hartmann <jhartmann@valinux.com>]

Timur Tabi wrote:

> ** Reply to message from Roman Zippel <roman@augan.com> on Thu, 25 Jan 2001
> 17:44:51 +0100
> 
> 
> 
>> set_bit(PG_reserved, &page->flags);
>> 	ioremap();
>> 	...
>> 	iounmap();
>> 	clear_bit(PG_reserved, &page->flags);
> 
> 
> The problem with this is that between the ioremap and iounmap, the page is
> reserved.  What happens if that page belongs to some disk buffer or user
> process, and some other process tries to free it.  Won't that cause a problem?

	The page can't belong to some other process/kernel component.  You own 
the page if you allocated it.  The kernel will only muck with memory you 
allocated if its GFP_HIGHMEM, or under certain circumstances if you map 
it into a user process (There are several rules here and I won't go into 
them, look at the DRM mmap setup for a start if your interested.)  This 
is the correct ordering of the calls (I was the one who added support to 
the kernel to ioremap real ram, trust me.)

-Jeff

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