KillMode=none replacement suggestions

[Mariusz Tkaczyk <mariusz.tkaczyk@xxxxxxxxxxxxxxx>]

Hi,
I'm coming here from linux-raid community. Coly proposed to remove
"Killmode=none" from our mdmon@.service[1]. Community accepted the change
because it is reasonable, the option will removed in the future. Now when the
change is incorporated with distributions we are observing hang tasks during
shutdown when the raid resource is mounted and systemd tries to umount it on
umount.target. Please take a look into this thread for details[2].

With "KillMode=none" process preserves systemd service stop, thus allows us to
proceed with shutdown. Removing it (and setting default) causes that process is
killed to early. I tried to fix that on multiple ways but I failed, see[3].

Ideally, we would like to have same behavior as with "Killmode=none" but
solution where service will be stopped after umount.target should be also
acceptable. Do you have any suggestions?

TIA,
Mariusz

[1]https://git.kernel.org/pub/scm/utils/mdadm/mdadm.git/commit/?id=52c67fcdd6dadc4138ecad73e65599551804d445
[2]https://lore.kernel.org/linux-raid/20220728110140.0000305a@xxxxxxxxxxxxxxx/
[3]https://lore.kernel.org/linux-raid/20220802174305.00000336@xxxxxxxxxxxxxxx/