From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Drebes Subject: [PATCH 2/2] Update documentation Date: Tue, 4 Dec 2007 13:02:32 +0100 Message-ID: <200712041302.33202.lists-receive@programmierforen.de> References: <200712041259.52118.lists-receive@programmierforen.de> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: linux-fsdevel@vger.kernel.org, Karel Zak , Andrew Morton , Christoph Hellwig , Phillip Lougher To: Linus Torvalds Return-path: Received: from server001.webpack.hosteurope.de ([80.237.130.9]:44801 "EHLO server001.webpack.hosteurope.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753202AbXLDMCu (ORCPT ); Tue, 4 Dec 2007 07:02:50 -0500 In-Reply-To: <200712041259.52118.lists-receive@programmierforen.de> Content-Disposition: inline Sender: linux-fsdevel-owner@vger.kernel.org List-ID: The following patch updates the cramfs documentation according to the changes in PATCH 1/2. The changes were tested on the following types of machines: An i386 compatible box (little endian) UltraSparc IIi (big endian) Signed-off-by: Andi Drebes --- README | 19 +++++-------------- 1 file changed, 5 insertions(+), 14 deletions(-) diff --git a/fs/cramfs/README b/fs/cramfs/README index 445d1c2..91efe77 100644 --- a/fs/cramfs/README +++ b/fs/cramfs/README @@ -6,8 +6,11 @@ a bit looser, e.g. it doesn't care if the items are swapped around (though it does care that directory entries (inodes) in a given directory are contiguous, as this is used by readdir). -All data is currently in host-endian format; neither mkcramfs nor the -kernel ever do swabbing. (See section `Block Size' below.) +All data is now in little endian format. Before, it was in host endian +format. In order to make filesystem images more shareable between machines +with a different byte order, cramfs' specification ("this README file") +was updated. There will be no support for big endian filesystems in the +future. : @@ -108,18 +111,6 @@ kernels, not even necessarily kernels of the same architecture if PAGE_CACHE_SIZE is subject to change between kernel versions (currently possible with arm and ia64). -The remaining options try to make cramfs more sharable. - -One part of that is addressing endianness. The two options here are -`always use little-endian' (like ext2fs) or `writer chooses -endianness; kernel adapts at runtime'. Little-endian wins because of -code simplicity and little CPU overhead even on big-endian machines. - -The cost of swabbing is changing the code to use the le32_to_cpu -etc. macros as used by ext2fs. We don't need to swab the compressed -data, only the superblock, inodes and block pointers. - - The other part of making cramfs more sharable is choosing a block size. The options are: