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From: Kautuk Consul <consul.kautuk@gmail.com>
Subject: Re: [PATCH] ARM: sparsemem: Enable =?utf-8?b?Q09ORklHX0hPTEVTX0lOX1pPTkU=?= config option for SparseMem and =?utf-8?b?SEFTX0hPTEVTX01FTU9SWU1PREVM?= for linux-3.0.
Date: Wed, 24 Aug 2011 12:31:51 +0000 (UTC)
Message-ID: <loom.20110824T142225-279@post.gmane.org>
References: <CAFPAmTQByL0YJT8Lvar1Oe+3Q1EREvqPA_GP=hHApJDz5dSOzQ@mail.gmail.com> <20110803110555.GD19099@suse.de> <CAFPAmTR79S3AVXrAFL5bMkhs2droL8THUCCPY23Ar5x_oftheQ@mail.gmail.com> <20110803132839.GG19099@suse.de> <CAFPAmTS2JEVk3tWhJN034dUmaxLujswmmsqGABGYEV=N3v0Ehw@mail.gmail.com> <20110804100928.GN19099@suse.de> <CAFPAmTQir8HnP2=WwPGSaWFu=hBS9=xT88f+XFFx5Hdf6zvGTA@mail.gmail.com> <20110805084742.GU19099@suse.de> <CAFPAmTS8-qQ4ZzBeJeKuG2jvyyfkwnqbtSjPX2TLddDPtSmF7g@mail.gmail.com>
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Hi Mel,


Kautuk Consul <consul.kautuk <at> gmail.com> writes:

> 
> Ok, I analyzed the code and it seems that this alignment problem has
> been solved by the changes made
> to the free_unused_memmap() code in arch/arm/mm/init.c.
> 
> I backported those changes to free_unused_memmap_node() in
> linux-2.6.35.9 and I don't see any more
> crashes. This solves my problem.
> 
> Thanks for all the help.


As per the email below, you might remember that I found a temporary 
solution by back-porting the free_unused_memmap_node() function in the 
arch/arm code.

The original issue was a crash in the move_freepages() function. 
The crash was happening because the pageblock pages was partially 
within one memory bank.

Can we solve this issue by modifying the check in move_freepages_block()
in the following manner: 
if (end_pfn >= zone->zone_start_pfn + zone->spanned_pages || 
    !PageBuddy(end_page))
    return 0;

This should take care of the crash situation as we will return 0 if
the end_page is lying outside a valid memory bank.

Do you agree with this change ?


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