Re: [PATCH] dracut: dmsquash-live: overlay module can be built-in the kernel

Crystal clear, thanks! I will submit a V2 patch using curly brackets

On Wed, May 04, 2022 at 12:03:26PM +0200, German Maglione wrote:
>On Tue, Apr 26, 2022 at 10:40 AM Federico Vaga <[email protected]> wrote:
>>
>> On Fri, Apr 22, 2022 at 01:04:45PM +0200, German Maglione wrote:
>> >On Wed, Apr 20, 2022 at 9:17 AM Federico Vaga <[email protected]> wrote:
>> >>
>> >> The dmsquash-live module assumes that `overlay` is always a module.
>> >> Therefore, when `overlay` is built-in the kernel, this module will fail
>> >> to detect the presence of such a feature.
>> >>
>> >> This patch adds a fallback mechanism to check also `/proc/filesystem`.
>> >> This is also what happens with the dracut NSF module when loading the
>> >> kernel module `rpc_pipefs`.
>> >>
>> >> Signed-off-by: Federico Vaga <[email protected]>
>> >> ---
>> >>  modules.d/90dmsquash-live/dmsquash-live-root.sh | 2 +-
>> >>  1 file changed, 1 insertion(+), 1 deletion(-)
>> >>
>> >> diff --git a/modules.d/90dmsquash-live/dmsquash-live-root.sh b/modules.d/90dmsquash-live/dmsquash-live-root.sh
>> >> index fd8a858a..b4a44e92 100755
>> >> --- a/modules.d/90dmsquash-live/dmsquash-live-root.sh
>> >> +++ b/modules.d/90dmsquash-live/dmsquash-live-root.sh
>> >> @@ -170,7 +170,7 @@ do_live_overlay() {
>> >>          fi
>> >>      fi
>> >>      if [ -n "$overlayfs" ]; then
>> >> -        if ! modprobe overlay; then
>> >> +        if ! (modprobe overlay || strstr "$(cat /proc/filesystems)" overlay); then
>> >
>> >if ! { modprobe overlay || strstr "$(cat /proc/filesystems)" overlay; }; then
>> >
>> >I recently made the same mistake of using a subshell.
>>
>> For my understanding:
>>
>> Why do you think it's a mistake to use a subshell?
>>
>> Are you thinking about execution performance, or some locale variable
>> that do not get exported to the subshell?
>
>Well, maybe "mistake" was not the best word to use in this case,
>the subshell here it's simply unnecessary
>
>> Then, why curly brackets and not double square brackets?
>
>do you mean like:
>if ! [[ modprobe overlay; ]]; then
>this is a mistake, you cannot wrap commands in [[ ]] (or []), try this:
>
>[[ false ]] && echo "you should not see this"
>
>> I see the latter is far more used among modules; even if it is
>> enforcing a dependency on bash (or whatever supports `[[`)
>
>That the hooks be posix compliant (as you said [[ can be considered as
>a bashism)
>is explicitly required In the dracut docs, although it is true that
>there are some hooks
>that use [[, but mostly setup scripts.
>
>>
>> Thanks in advance for the clarifications :)
>>
>> >>              if [ "$overlayfs" = required ]; then
>> >>                  die "OverlayFS is required but not available."
>> >>                  exit 1
>> >> --
>> >> 2.27.0
>> >>
>> >
>> >
>> >--
>> >German
>> >
>>
>
>
>-- 
>German
>