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Date:   Tue, 30 Mar 2021 13:50:23 +0200
From:   Oleksandr Natalenko <oleksandr@natalenko.name>
To:     Piotr Gorski <lucjan.lucjanov@gmail.com>
Cc:     linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org,
        Masahiro Yamada <masahiroy@kernel.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Kees Cook <keescook@chromium.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Valentin Schneider <valentin.schneider@arm.com>,
        "Jan Alexander Steffens (heftig)" <jan.steffens@gmail.com>,
        Nick Terrell <terrelln@fb.com>,
        David Howells <dhowells@redhat.com>,
        Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH] init: add support for zstd compressed modules
Message-ID: <20210330115023.qt742qsdekwiroey@spock.localdomain>
References: <20210330113235.2767216-1-lucjan.lucjanov@gmail.com>
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On Tue, Mar 30, 2021 at 01:32:35PM +0200, Piotr Gorski wrote:
> kmod 28 supports modules compressed in zstd format so let's add this possibility to kernel.
> 
> Signed-off-by: Piotr Gorski <lucjan.lucjanov@gmail.com>
> ---
>  Makefile     | 7 +++++--
>  init/Kconfig | 9 ++++++---
>  2 files changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 5160ff8903c1..82f4f4cc2955 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1156,8 +1156,8 @@ endif # INSTALL_MOD_STRIP
>  export mod_strip_cmd
>  
>  # CONFIG_MODULE_COMPRESS, if defined, will cause module to be compressed
> -# after they are installed in agreement with CONFIG_MODULE_COMPRESS_GZIP
> -# or CONFIG_MODULE_COMPRESS_XZ.
> +# after they are installed in agreement with CONFIG_MODULE_COMPRESS_GZIP,
> +# CONFIG_MODULE_COMPRESS_XZ, or CONFIG_MODULE_COMPRESS_ZSTD.
>  
>  mod_compress_cmd = true
>  ifdef CONFIG_MODULE_COMPRESS
> @@ -1167,6 +1167,9 @@ ifdef CONFIG_MODULE_COMPRESS
>    ifdef CONFIG_MODULE_COMPRESS_XZ
>      mod_compress_cmd = $(XZ) --lzma2=dict=2MiB -f
>    endif # CONFIG_MODULE_COMPRESS_XZ
> +  ifdef CONFIG_MODULE_COMPRESS_ZSTD
> +    mod_compress_cmd = $(ZSTD) -T0 --rm -f -q
> +  endif # CONFIG_MODULE_COMPRESS_ZSTD
>  endif # CONFIG_MODULE_COMPRESS
>  export mod_compress_cmd
>  
> diff --git a/init/Kconfig b/init/Kconfig
> index 8c2cfd88f6ef..86a452bc2747 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -2250,8 +2250,8 @@ config MODULE_COMPRESS
>  	bool "Compress modules on installation"
>  	help
>  
> -	  Compresses kernel modules when 'make modules_install' is run; gzip or
> -	  xz depending on "Compression algorithm" below.
> +	  Compresses kernel modules when 'make modules_install' is run; gzip,
> +	  xz, or zstd depending on "Compression algorithm" below.
>  
>  	  module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
>  
> @@ -2273,7 +2273,7 @@ choice
>  	  This determines which sort of compression will be used during
>  	  'make modules_install'.
>  
> -	  GZIP (default) and XZ are supported.
> +	  GZIP (default), XZ, and ZSTD are supported.
>  
>  config MODULE_COMPRESS_GZIP
>  	bool "GZIP"
> @@ -2281,6 +2281,9 @@ config MODULE_COMPRESS_GZIP
>  config MODULE_COMPRESS_XZ
>  	bool "XZ"
>  
> +config MODULE_COMPRESS_ZSTD
> +	bool "ZSTD"
> +
>  endchoice
>  
>  config MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS
> -- 
> 2.31.0.97.g1424303384
> 

Great!

Reviewed-by: Oleksandr Natalenko <oleksandr@natalenko.name>

This works perfectly fine in Arch Linux if accompanied by the
following mkinitcpio amendment: [1].

I'm also Cc'ing other people from get_maintainers output just
to make this submission more visible.

Thanks.

[1] https://github.com/archlinux/mkinitcpio/pull/43

-- 
  Oleksandr Natalenko (post-factum)