Message-ID: <465534B9.2030105@de.ibm.com>
Date: Thu, 24 May 2007 08:46:17 +0200
From: Carsten Otte <cotte@de.ibm.com>
Reply-To: carsteno@de.ibm.com
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To: richard.griffiths@windriver.com
CC: carsteno@de.ibm.com, Andrew Morton <akpm@linux-foundation.org>,
       Linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2.6.21] cramfs: add cramfs Linear XIP
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Richard Griffiths (wrs) wrote:
> One question I have is the difference in the two models. If I understand
> correctly the filemap_xip expects the ext2 to mount as XIP while the
> Linear Cramfs only enables XIP for apps that have the sticky bit set.
> Hence the Application XIP moniker.
> Does the filemap_xip expect the entire filesystem is XIP?
The file operations from filemap_xip are only effective if the struct 
file_operations vector refers to them (see ext2_xip_file_operations in 
fs/ext2/file.c as example). In oder to function proper, the 
corresponding address_space_operations vector needs to provide an 
implementation of get_xip_page (see ext2_get_xip_page in 
fs/ext2/xip.c). Both vectors are per inode, one can chose to have XIP 
for individual files in a file system.

so long,
Carsten
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