Message-ID: <46553744.4000403@de.ibm.com>
Date: Thu, 24 May 2007 08:57:08 +0200
From: Carsten Otte <cotte@de.ibm.com>
Reply-To: carsteno@de.ibm.com
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To: Jared Hulbert <jaredeh@gmail.com>
CC: carsteno@de.ibm.com, Andrew Morton <akpm@linux-foundation.org>,
       richard.griffiths@windriver.com,
       Richard Griffiths <res07ml0@verizon.net>, Linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2.6.21] cramfs: add cramfs Linear XIP
References: <1179871779.24163.11.camel@localhost.localdomain> <20070522154905.1d7e8a2e.akpm@linux-foundation.org> <4653F264.1030807@de.ibm.com> <6934efce0705231021x6cc45c61kf253eae185504611@mail.gmail.com>
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Jared Hulbert wrote:
>> To me, it looks like this
>> work can be modified to use filemap_xip.
> 
> How?
First, get a struct page behind the subject file system image. A good 
idea to get there is to use vmem_map, which allows have a 
discontiguous mem_map array in virtual storage. Then add the memory 
segment's address range to it. Sparsemem also helps, if vmem_map is 
not available.

Second, implement get_xip_page for this file system. This address 
space operation needs to be provided for all files that are supposed 
to be XIP. readpage(s)/writepage(s) should not be provided for these 
files, becuase they rely on using the page cache.

Third, use file operations from mm/filemap_xip.c.

so long,
Carsten
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