Re: [PATCH] expand-on-first-boot: Fix early exit in helper script

[Henning Schild <henning.schild@siemens.com>]

Am Fri, 10 Jun 2022 10:13:54 +0300
schrieb Uladzimir Bely <ubely@ilbers.de>:

> In the email from Friday, 10 June 2022 08:14:19 +03 user Jan Kiszka
> wrote:
> > On 10.06.22 05:19, Uladzimir Bely wrote:  
> > > Changes in 342a751e introduced a regression when error from 'find'
> > > makes helper script early exit (with -1 error code) just after an
> > > attempt to assign ROOT_DEV_SLAVE variable. So, the last partition
> > > remained not resized.
> > > 
> > > Passing 'find' output to 'head -1' masks possible error from
> > > 'find' without breaking the logic and continues the script
> > > execution.
> > > 
> > > Signed-off-by: Uladzimir Bely <ubely@ilbers.de>
> > > ---
> > > 
> > >  .../expand-on-first-boot/files/expand-last-partition.sh
> > > | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git
> > > a/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.s
> > > h
> > > b/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.s
> > > h index f3e29a1c..934a014f 100755
> > > ---
> > > a/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.s
> > > h +++
> > > b/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.s
> > > h @@ -11,7 +11,7 @@ set -e
> > > 
> > >  ROOT_DEV="$(findmnt / -o source -n)"
> > >  ROOT_DEV_NAME=${ROOT_DEV##*/}
> > > 
> > > -ROOT_DEV_SLAVE=$(find /sys/block/"${ROOT_DEV_NAME}"/slaves
> > > -mindepth 1 -print -quit 2>/dev/null) +ROOT_DEV_SLAVE=$(find
> > > /sys/block/"${ROOT_DEV_NAME}"/slaves -mindepth 1 -print -quit
> > > 2>/dev/null | head -1)> 
> > >  if [ -n "${ROOT_DEV_SLAVE}" ]; then
> > >  
> > >  	ROOT_DEV=/dev/${ROOT_DEV_SLAVE##*/}
> > >  
> > >  fi  
> > 
> > "-quit" is supposed to obsolete "head -1". Feel free to prove me
> > wrong, but that was the reason for dropping it.
> > 
> > Jan  
> 
> Yes, "-quit" makes 'find' to exit after first match. But if nothing
> found, the return code of 'find' is "-1" and due to script's "set -e"
> it just exits.
> 
> An example that demonstrates the behaviour (on raspberry):
> 
> root@isar:~# cat /boot/test.sh  
> #!/bin/sh 
> 
> set -e 
> 
> echo "1: start" 
> ROOT_DEV="$(findmnt / -o source -n)" 
> echo "2: ROOT_DEV=${ROOT_DEV}" 
> ROOT_DEV_NAME=${ROOT_DEV##*/} 
> echo "3: ROOT_DEV_NAME=${ROOT_DEV_NAME}" 
> ROOT_DEV_SLAVE=$(find /sys/block/"${ROOT_DEV_NAME}"/slaves -mindepth
> 1 -print -quit 
> 2>/dev/null)   
> echo "4: ROOT_DEV_SLAVE=${ROOT_DEV_SLAVE}" 
> root@isar:~# sh /boot/test.sh  
> 1: start 
> 2: ROOT_DEV=/dev/mmcblk0p2 
> 3: ROOT_DEV_NAME=mmcblk0p2 
> root@isar:~# echo $? 
> 1 
> root@isar:~# ls /sys/block/ | grep mmc 
> mmcblk0 
> root@isar:~# 
> So, the easiest way to mask error returned by 'find' is to use
> something like 'head -1' or 'tee / dev/null'. In this case script
> just continues with empty ROOT_DEV_SLAVE.

i think something other than head would be better to catch the case
where find does not find anything.

i.e.

rc=0
find || rc=$?
if [ $rc -eq 0 -a -n "${ROOT_DEV_SLAVE}" ]; then

or simply use a "find || true"

Henning