Re: [PATCH v5 02/22] liveupdate: luo_core: integrate with KHO

Hi Mike,

Thank you for review, my comments below:

quoted

This is why this call is placed first in reboot(), before any
irreversible reboot notifiers or shutdown callbacks are performed. If
an allocation problem occurs in KHO, the error is simply reported back
to userspace, and the live update update is safely aborted.

This is fine. But what I don't like is that we can't use kho without
liveupdate. We are making debugfs optional, we have a way to call

Yes you can: you can disable liveupdate (i.e. not supply liveupdate=1
via kernel parameter) and use KHO the old way: drive it from the
userspace. However, if liveupdate is enabled, liveupdate becomes the
driver of KHO as unfortunately KHO has these weird states at the
moment.

kho_finalize() on the reboot path and it does not seem an issue to do it
even without liveupdate. But then we force kho_finalize() into
liveupdate_reboot() allowing weird configurations where kho is there but
it's unusable.

What do you mean KHO is there but unusable, we should not have such a state...

What I'd like to see is that we can finalize KHO on kexec reboot path even
when liveupdate is not compiled and until then the patch that makes KHO
debugfs optional should not go further IMO.

Another thing I didn't check in this series yet is how finalization driven
from debugfs interacts with liveupdate internal handling?

I think what we can do is the following:
- Remove "Kconfig: make debugfs optional" from this series, and
instead make that change as part of stateless KHO work.
- This will ensure that when liveupdate=0 always KHO finalize is fully
support the old way.
- When liveupdate=1 always disable KHO debugfs "finalize" API, and
allow liveupdate to drive it automatically. It would add another
liveupdate_enable() check to KHO, and is going to be removed as part
of stateless KHO work.

Pasha