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Re: Problems booting Linux 2.6.18.1 on MIPS34K core

To: Trevor Hamm <Trevor_Hamm@pmc-sierra.com>
Subject: Re: Problems booting Linux 2.6.18.1 on MIPS34K core
From: Ralf Baechle <ralf@linux-mips.org>
Date: Wed, 22 Nov 2006 21:58:04 +0000
Cc: "'Atsushi Nemoto'" <anemo@mba.ocn.ne.jp>, linux-mips@linux-mips.org
In-reply-to: <E8C8A5231DDE104C816ADF532E0639120194F4EB@bby1exm07.pmc_nt.nt.pmc-sierra.bc.ca>
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On Wed, Nov 22, 2006 at 12:31:10PM -0800, Trevor Hamm wrote:

> The source of the problem seems to be with squashfs.  When I compare booting 
> a kernel using squashfs to one using cramfs (which always seems to boot 
> successfully on power-up), both are reading the troublesome page from 
> /lib/ld-uClibc.so, and both are calling flush_dcache_page() on this page.  
> But in the case of cramfs, flush_dcache_page() causes an immediate cache 
> flush of that page (mapping_mapped(mapping) in __flush_dcache_page() is 
> returning non-zero), while squashfs just marks the page as dirty and defers 
> the cache flush (mapping_mapped(mapping) is returning zero).  I have no idea 
> what causes this difference in behaviour, but right now it appears to be a 
> bug in squashfs rather than the linux-mips kernel.

There are a few other potencial and real bugs me and Atsushi have found
in squashfs.  Guess there is a reason why it's not yet in the kernel ...
I'm still waiting for feedback from the squashfs author.

  Ralf

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