x86, bcm27xx: is squashfs+f2fs layout (rather than ext4) actively supported?

[Lukas Zeller]

Hello,

sorry for asking again, but I'm really stuck and seeking help/hints
about how to proceed with two issues that break sysupgrade at least
for bcm27xx (RPi) targets which use squashfs+f2fs:

- sysupgrading from a smaller to a larger /boot partition size bricks
  devices because something (f2fs?) keeps holding on the second
  partition, preventing unmounting it, preventing mounting the larger
  /boot (because it overlaps), preventing sysupgrade.tgz to be saved as
  it should. Details in [1].

- sysupgrading can occasionally fail depending on data following the
  squashfs part on disk, because there is no padding that would ensure
  mount_root cannot possibly interpret that data as start of an f2fs.
  Details in [2],[3].

As there was very little response to [1..3], I wonder if using
squashfs+f2fs on bcm27xx (and x86) might be a not really supported
option at all? At least, it seems to be a very rarely used option?

I would like to contribute fixes for these issues, and spent a lot of
time to analyze both of them, and think I pretty much could find the
exact reasons.

However I am stuck with [1] technically (no more ideas how to free the
busy partition), and while I could probably hack something for [2] on
bcm27xx, seeing that the same mechanism is used in x86's and serveral
other target's platform.sh, I'd prefer a more informed path of
actions ;-)

I don't expect others to fix this, but I really need some input from
knowledgeable OpenWrt devs to get any further with this. And if it's
only stating squashfs+f2fs is something one should NOT actually use on
these non-mtd platforms at all.

Thanks in advance
Lukas

[1] https://forum.openwrt.org/t/raspberrypi-sysupgrade-looses-overlay-when-boot-partition-gets-bigger/139138/2

[2] http://lists.openwrt.org/pipermail/openwrt-devel/2023-May/041062.html
[3] https://forum.openwrt.org/t/broken-f2fs-after-sysupgrade-on-rpi-config-not-restored/159703

--
Lukas Zeller, plan44.ch
luz at plan44.ch - https://plan44.ch