linux-kernel - Re: 2.6.24-rc5-mm1: problems with cat /proc/kpageflags

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Date:	Thu, 20 Dec 2007 16:17:26 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	m.kozlowski@...land.pl
Cc:	mpm@...enic.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org
Subject: Re: 2.6.24-rc5-mm1: problems with cat /proc/kpageflags

From: Mariusz Kozlowski <m.kozlowski@...land.pl>
Date: Thu, 20 Dec 2007 20:47:55 +0100

> [  145.128915] TSTATE: 0000004411009603 TPC: 00000000005119ac TNPC: 00000000005119b0 Y: 00000000    Not tainted
> [  145.128940] TPC: <kpagecount_read+0x94/0xe0>

My suspicion at this point is that with certain RAM layouts, simply
iterating over PFN's is simply not working out.

pfn_to_page() seems to be doing no range checking, and with sparsemem
vmemmap, which sparc64 always uses, this can be problematic.

It just blindly goes "vmemmap + pfn" which is asking for trouble, in
particular when the physical RAM layout really is sparse.

Maybe it's enough to add a pfn_valid() check here?  If pfn_valid()
means there is a vmemmap translation setup for that page struct too,
it would work.
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