Re: [RFC PATCH v4] kdumpctl: don't always rebuild when extra_modules is set

[Dave Young]

On 04/30/19 at 01:15pm, Kairui Song wrote:
> We don't necessarily have to always rebuild the initramfs when
> extra_modules is set, instead just detect if any module is updated
> and only rebuild initramfs if found any updated kernel module.

Hi Kairui,

About the DUP modules, probably it is RHEL only, but probably in Fedora
it also has something related, I found below thread about weak updates:
https://lists.fedoraproject.org/pipermail/devel/2006-August/088293.html

So it is worth to dig it and do some tests.
> Signed-off-by: Kairui Song
>
> kdumpctl | 38 +++++++++++++++++++++++++++++++++-----
>  1 file changed, 33 insertions(+), 5 deletions(-)
>
> diff --git a/kdumpctl b/kdumpctl
> index 3f80ba4..f2e2b76 100755
> --- a/kdumpctl
> +++ b/kdumpctl
> @@ -486,6 +486,34 @@ check_wdt_modified()
>    return 1
>  }
>
> +# Check if any extra kernel is changed
> +check_kmodules_modified()
> +{
> local _extra_modules="$(grep ^extra_modules $KDUMP_CONFIG_FILE | sed 's/^extra_modules\s*//')"
> local _modified_modules
> # Check for any updated module
> for _module in $_extra_modules; do
> _module_file="$(modinfo -k "$kdump_kver" -n "$_module" 2>/dev/null)"
> if [[ -n "$_module_file" ]]; then
> 	_time_stamp="$(stat -c "%Y" "$_module_file")"
> 	if [ "$_time_stamp" -gt "$image_time" ]; then
> 		_modified_modules+="$_module "

Here once we found a module is changed then we can just print some msg
and return 1, so that we can reduce the kdumpctl checking time.
> 	fi
> fi
> done
> if [[ -n "$_modified_modules" ]]; then
> echo "Detected change(s) of following kernel modules:"
> for _module in $_modified_modules; do
> 	echo "$_module"
> done
> return 1
> fi
> return 0
>
> +}
>
> # returns 0 if system is not modified
>  # returns 1 if system is modified
>  # returns 2 if system modification is invalid
> @@ -513,12 +541,16 @@ check_system_modified()
>    	return 1
>    fi
> check_kmodules_modified
> if [ $? -ne 0 ]; then
> return 1
> fi

There is a function check_files_modified(), another way is just return
the filenames and let check_files_modified() to check the timestamps.
But I'm not sure which way use less time, maybe do some tests and choose
a better one?
> return 0
>  }
>
> check_rebuild()
>  {
> local extra_modules
> local capture_capable_initrd="1"
> local _force_rebuild force_rebuild="0"
> local _force_no_rebuild force_no_rebuild="0"
>
> @@ -558,10 +590,6 @@ check_rebuild()
>    	return 0
>    fi
> #will rebuild every time if extra_modules are specified
> extra_modules=`grep ^extra_modules $KDUMP_CONFIG_FILE`
> [ -n "$extra_modules" ] && force_rebuild="1"
> #check to see if dependent files has been modified
>  #since last build of the image file
>  if [ -f $TARGET_INITRD ]; then
>
> -- 
> 2.20.1