Bug in 21.02.0-rc3 for Friendlyarm R2S: sysupgrade keeps complete overlay data active after upgrade (squashfs)

[mdiehm]

UPDATE: I should have first looked at bugs.openwrt.org - this has been reported for a while but not fixed so far.

https://bugs.openwrt.org/index.php?do=details&task_id=3798&string=overlay&type[0]=&sev[0]=&pri[0]=&due[0]=&reported[0]=&cat[0]=&status[0]=open&percent[0]=&opened=&dev=&closed=&duedatefrom=&duedateto=&changedfrom=&changedto=&openedfrom=&openedto=&closedfrom=&closedto=

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Overlay data is kept after sysupgrades and thus breaks upgrades.

Test:

1. Install fresh image
2. boot
3. touch /root/foo /etc/bar
4. sysupgrade -n -v openwrt-21.02.0-rc3-rockchip-armv8-friendlyarm_nanopi-r2s-squashfs-sysupgrade.img.gz

after boot the files /root/foo and /etc/bar are still there potentially hiding what sits in /rom/etc/bar if it existed. If I manually add a jff2reset to the sysupgrade scripts, the upgrade behaves like it should. Any ideas why this is happening?

Tested and validated on: Friendlyarm R2S with 21.02.0-rc3 and snaptshot image:
https://downloads.openwrt.org/releases/21.02.0-rc3/targets/rockchip/armv8/openwrt-21.02.0-rc3-rockchip-armv8-friendlyarm_nanopi-r2s-squashfs-sysupgrade.img.gz

[mdiehm]

https://bugs.openwrt.org/index.php?do=details&task_id=3798&string=overlay&type[0]=&sev[0]=&pri[0]=&due[0]=&reported[0]=&cat[0]=&status[0]=open&percent[0]=&opened=&dev=&closed=&duedatefrom=&duedateto=&changedfrom=&changedto=&openedfrom=&openedto=&closedfrom=&closedto=