Re: [PATCH v3] Seperate dracut and dracut-squash compressor for zstd

[Coiby Xu]

Hi Tao,

On Fri, Sep 23, 2022 at 07:36:18PM +0800, Tao Liu wrote:
> Previously kexec-tools will pass "--compress zstd" to
> dracut. It
> will make dracut to decide whether: a) call mksquashfs to make a
> zstd format squash-root.img, b) call cmd zstd to make a initramfs.
>
> Since dracut(>= 057) has decoupled the compressor for dracut and
> dracut-squash, So in this patch, we will pass the compressor seperately.
>
> Note:
>
> The is_squash_available && !dracut_has_option --squash-compressor
> && !is_zsdt_command_available case is left unprocessed on purpose.
>
> Actually, the situation when we want to call zstd compression is:
> 1) If squash function OK, we want dracut to invoke mksquashfs to make
> a zstd format squash-root.img within initramfs.
> 2) If squash function is not OK, and cmd zstd presents, we want dracut
> to invoke cmd zstd to make a zstd format initramfs.
>
> is_zstd_command_available check can handle case 2 completely.
>
> However, for the is_squash_available check, it cannot handle case 1
> completely. It only checks if the kernel supports squashfs, it doesn't
> check whether the squash module has been added by dracut when making
> initramfs. In fact, in kexec-tools we are unable to do the check,
> there are multiple ways to forbit dracut to load a module, such as
> "dracut -o module" and "omit_dracutmodules in dracut.conf".
>
> When squash dracut module is omitted, is_squash_available check will
> still pass, so "--compress zstd" will be appended to dracut cmdline,
> and it will call cmd zstd to do the compression. However cmd zstd may
> not exist, so it fails.
>
> The previous "--compress zstd" is ambiguous, after the intro of
> "--squash-compressor", "--squash-compressor" only effect for
> mksquashfs and "--compress" only effect for specific cmd.
>
> So for the is_squash_available && !dracut_has_option
> --squash-compressor && !is_zsdt_command_available case, we just leave
> it to be handled the default way.
>
> Reviewed-by: Philipp Rudo <prudo(a)redhat.com&gt;
> Signed-off-by: Tao Liu <ltao(a)redhat.com&gt;
> ---
> v1 -> v2:
> 1) Add a checker if dracut doesn't have "--squash-compressor"
>    option.
> 2) Removed the "Recommends: zstd" in spec file. Since it is optional
>    and won't break any function if not present.
>
> v2 -> v3: updated the commit log.
> ---
>  kdump-lib.sh     | 8 +++++++-
>  kexec-tools.spec | 1 -
>  mkdumprd         | 7 +++----
>  mkfadumprd       | 4 +++-
>  4 files changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/kdump-lib.sh b/kdump-lib.sh
> index 4b88908..f93e7d6 100755
> --- a/kdump-lib.sh
> +++ b/kdump-lib.sh
> @@ -37,6 +37,12 @@ is_zstd_command_available()
>  	[[ -x "$(command -v zstd)" ]]
>  }
>
> +dracut_have_option()
> +{
> +	local _option=$1
> +	! $(dracut "$_option" 2>&1 | grep -q "unrecognized option")
> +} 
shellcheck catches an issue [1], 

In kdump-lib.sh line 45:
	! $(dracut "$_option" 2>&1 | grep -q "unrecognized option")
           ^-- SC2091 (warning): Remove surrounding $() to avoid executing output (or use
eval if intentional).

[1] https://github.com/coiby/kexec-tools/actions/runs/3148610706/jobs/5119328225
> +
>  perror_exit()
>  {
>  	derror "$@"
> @@ -458,7 +464,7 @@ is_wdt_active()
>  have_compression_in_dracut_args()
>  {
>  	[[ "$(kdump_get_conf_val dracut_args)" =~ \
> -		(^|[[:space:]])--(gzip|bzip2|lzma|xz|lzo|lz4|zstd|no-compress|compress)([[:space:]]|$)
> ]]
> +		(^|[[:space:]])--(gzip|bzip2|lzma|xz|lzo|lz4|zstd|no-compress|compress|squash-compressor)([[:space:]]|$)
> ]]
>  }
>
>  # If "dracut_args" contains "--mount" information, use it
> diff --git a/kexec-tools.spec b/kexec-tools.spec
> index ee43b13..c829bbe 100644
> --- a/kexec-tools.spec
> +++ b/kexec-tools.spec
> @@ -64,7 +64,6 @@ Requires: dracut >= 050
>  Requires: dracut-network >= 050
>  Requires: dracut-squash >= 050
>  Requires: ethtool
> -Recommends: zstd
>  Recommends: grubby
>  Recommends: hostname
>  BuildRequires: make
> diff --git a/mkdumprd b/mkdumprd
> index c0f131d..f553b45 100644
> --- a/mkdumprd
> +++ b/mkdumprd
> @@ -432,10 +432,9 @@ done <<< "$(kdump_read_conf)"
>  handle_default_dump_target
>
>  if ! have_compression_in_dracut_args; then
> -	# Here zstd is set as the default compression method. If squash module
> -	# is available for dracut, libzstd will be used by mksquashfs. If
> -	# squash module is unavailable, command zstd will be used instead.
> -	if is_squash_available || is_zstd_command_available; then
> +	if is_squash_available && dracut_have_option "--squash-compressor";
> then
> +		add_dracut_arg "--squash-compressor" "zstd"
> +	elif is_zstd_command_available; then
>  		add_dracut_arg "--compress" "zstd"
>  	fi
>  fi
> diff --git a/mkfadumprd b/mkfadumprd
> index 86dfcee..f353f15 100644
> --- a/mkfadumprd
> +++ b/mkfadumprd
> @@ -64,7 +64,9 @@ fi
>
>  # Same as setting zstd in mkdumprd
>  if ! have_compression_in_dracut_args; then
> -	if is_squash_available || is_zstd_command_available; then
> +	if is_squash_available && dracut_have_option "--squash-compressor";
> then
> +		_dracut_isolate_args+=(--squash-compressor zstd)
> +	elif is_zstd_command_available; then
>  		_dracut_isolate_args+=(--compress zstd)
>  	fi
>  fi
> -- 
> 2.33.1
>  
-- 
Best regards,
Coiby