Re: ioremap_nocache problem?

[Roman Zippel <roman@augan.com>]

Hi,

Timur Tabi wrote:

> I mark the page as reserved when I ioremap() it.  However, if I leave it marked
> reserved, then iounmap() will not unmap it.  If I mark it "unreserved" (i.e.
> reset the reserved bit), then iounmap will unmap it, but it will decrement the
> page counter to -1 and the whole system will crash soon thereafter.
> 
> I've been asking about this problem for months, but no one has bothered to help
> me out.

The order is important:

	get_free_page();
	set_bit(PG_reserved, &page->flags);
	ioremap();
	...
	iounmap();
	clear_bit(PG_reserved, &page->flags);
	free_page();

Alternatively something like this should also be possible:

	get_free_page();
	ioremap();
	...
	iounmap();

nopage() {
	...
	atomic_inc(&page->count);
	return page;
}

But I never tried this version, so I can't guarantee anything. :)

bye, Roman
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