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From: Kumar Gala <galak@kernel.crashing.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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Subject: CONFIG_DEBUG_PAGEALLOC generates WARN_ON() in ppc32 hash
Date: Fri, 27 Mar 2009 06:56:05 -0500
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Ben,

If we have CONFIG_DEBUG_PAGEALLOC enabled we end up hitting the  
WARN_ON() in set_pte_at() when we boot.  This appears because we've  
already setup pte's via mapin_ram() after which we end up calling  
kernel_map_pages().

So I'm not sure if __change_page_attr() should be doing something  
different or if the WARN_ON() should be conditional on ! 
CONFIG_DEBUG_PAGEALLOC

- k