[PATCH] ARM: Fix virtual kernel memory printing for sparsemem

[Russell King - ARM Linux]

On Tue, May 04, 2010 at 06:13:28PM +0200, Marek Vasut wrote:
> Dne Čt 25. března 2010 17:01:26 Catalin Marinas napsal(a):
> > On Thu, 2010-03-25 at 15:30 +0000, Russell King - ARM Linux wrote:
> > > On Thu, Mar 25, 2010 at 03:24:29PM +0000, Catalin Marinas wrote:
> > > > On Thu, 2010-03-25 at 15:10 +0000, Russell King - ARM Linux wrote:
> > > > > While this looks fine, I'd like to see a lot of Tested-by's against
> > > > > this before it's merged - we've had similar code in show_mem()
> > > > > which has proven to be quite problematical to get right for all the
> > > > > various different combinations we have.
> > > > > 
> > > > > However, we also have the same method in show_mem() which we know
> > > > > works fine, so I'd also like to see the problem with using it in
> > > > > mem_init() fully analysed - rather than a "possibly because".
> > > > 
> > > > I can remove the "possibly" part :). The page_count() is given a page
> > > > with some random flags and it thinks it's a compound page. It than
> > > > tries to access page->first which isn't set, hence the error.
> > > > 
> > > > The original code assumes that for a given node the map is contiguous
> > > > and it calculates the page as (map + pfn). This is only true for
> > > > flatmem. With sparsemem the page calculation is a bit more complicated
> > > > but handled by pfn_to_page().
> > > 
> > > And show_mem() ?  It seems to suffer from the same problem.
> > 
> > And that's a patch which fixes both (but as you said, it would be good
> > if more people test it on various platforms).
> > 
> > 
> > ARM: Fix kernel memory printing for sparsemem
> > 
> > From: Catalin Marinas <catalin.marinas at arm.com>
> > 
> > The show_mem() and mem_init() function are assuming that the page map is
> > contiguous and calculates the start and end page of a bank using (map +
> > pfn). This fails with SPARSEMEM where pfn_to_page() must be used.
> > 
> > Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
> > Cc: Will Deacon <Will.Deacon at arm.com>
> > Cc: Andreas Fenkart <andreas.fenkart at streamunlimited.com>
> 
> Works perfectly on my machine. I have a PXA270 based device where I have to use 
> sparsemem. Thanks, you can add my:
> 
> Tested-by: Marek Vasut <marek.vasut at gmail.com>
> 
> Russell, the patch looks fine, please apply, the stuff is really broken.

It's great to see patches getting tested by others ;)

Catalin - mind submitting this with Marek's tested-by please?