Re: [RFC][patch 0/2] mm: remove PageReserved

Nick Piggin
2005-08-11T09:09:29Z

Benjamin Herrenschmidt wrote:
> On Tue, 2005-08-09 at 20:41 +0100, Russell King wrote:
>
>>On Tue, Aug 09, 2005 at 07:38:52AM -0700, Martin J. Bligh wrote:
>>
>>>pfn_valid() doesn't tell you it's RAM or not - it tells you whether you
>>>have a backing struct page for that address. Could be an IO mapped device,
>>>a small memory hole, whatever.
>>
>>The only things which have a struct page is RAM. Nothing else does.
>
>
> Well, not anymore :)
>

Well thanks everyone for the discussion and input. If I have missed
answering a question, please just mail me privately to let me know.

I guess that despite some architecture implementation differences,
everyone will be happy to see PageReserved go from core code. So
I will send Andrew the patches.

After that, we have a few options to move forward with completely
getting rid of the flag from the other funny places it has cropped
up. A portable page_is_ram() sounds like the best way to go, as it
would not use up a page flag.

As far as ioremap goes - I would rather completely disallow it from
remapping physical pages and enforce that where possible (eg. with
page_is_ram()).

However, these issues (page_is_ram, swsusp, ioremap) need not be
tackled right now. I will bring them up on the lists some time after
the core mm/ is working nicely without PageReserved.

Thanks,
Nick

--
SUSE Labs, Novell Inc.

Send instant messages to your online friends http://au.messenger.yahoo.com