linux-kernel - Re: [PATCH] Compress kernel modules on installation.

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Message-ID: <20080225222137.GY8953@1wt.eu>
Date:	Mon, 25 Feb 2008 23:21:38 +0100
From:	Willy Tarreau <w@....eu>
To:	Steve Brokenshire <sbrokenshire@...tia.co.uk>
Cc:	linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org
Subject: Re: [PATCH] Compress kernel modules on installation.

On Mon, Feb 25, 2008 at 09:42:09PM +0000, Steve Brokenshire wrote:
> Hi,
> 
> (I've sent this to the linux-kbuild and linux-kernel lists as this
> patch modifies the Makefile.modinst file. I also don't subscribe to the 
> linux-kbuild and linux-kernel mailing lists so can I have any replies
> CC'ed to me please)
> 
> This patch allows kernel modules to be compressed when 'make
> modules_install' is run after being copied to
> the /lib/module/<version>/<...> directory which is useful if you have
> module-init-tools installed with --enable-zlib. This patch adds an
> option (MODULE_COMPRESS) to the kernel configuration file (specifically
> init/Kconfig) so that the kernel modules will compressed if
> MODULE_COMPRESS is set.
> 
> When MODULE_COMPRESS is set the output of 'make modules_install' will
> go as the following:
> 
> INSTALL  drivers/fs/xfs/xfs.ko
> COMPRESS drivers/fs/xfs/xfs.ko
> INSTALL  drivers/fs/fat/fat.ko
> COMPRESS drivers/fs/fat/fat.ko
> ...
> 
> I've tested my patch on kernel versions 2.6.24.2, 2.6.24-git12, 2.6.23.14 and
> 2.6.19 and they compile, install and compress into the respective
> module directories without any errors.
> 
> I've also tested this with the uvcvideo (linux-uvc) kernel module (from
> the SVN branch and with kernel versions 2.6.24.2, 2.6.24-git12, 2.6.23.14 and
> 2.6.19) as that uses Kbuild properly when installing the module and
> after installing the uvcvideo the module is then compressed.
> Unfortunately, I couldn't find any other kernel modules which used the
> Kbuild system for installing their kernel modules. :(
> 
> I've included include/config/auto.conf in Makefile.modinst so that it
> can check if MODULE_COMPRESS is set when installing the kernel modules.
> 
> Unfortunately when I ran mkinitrd (CentOS version) to create the initrd
> image to go with the kernel, I get errors saying that certain kernel
> modules don't exist despite the fact they do actually exist. When I
> pass --allow-missing to mkinitrd, it seems to go fine but when booting
> up with the system with the new initrd image I get error messages
> saying that the modules don't exist.
> 
> A workaround is to compile the modules, don't have MODULE_COMPRESS set 
> in .config, install the modules, run mkinitrd and copy it to /boot, set 
> MODULE_COMPRESS in .config and then install the modules again but
> compressed.
> 
> That's about it really. The only showstopper I feel is mkinitrd not
> working properly with the compressed kernel modules.

Have you tried keeping the module names intact (.ko, not .ko.gz) ?
It's what I was doing with modutils in 2.4 and what I'm still doing
with module-init-tools in 2.6. While I don't particularly use mkinitrd,
I think that keeping the name intact is preferable and should help.

Regards,
Willy

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