Re: [RFC v2 11/16] luo: luo_sysfs: add sysfs state monitoring

[Pasha Tatashin]

On Thu, Jun 5, 2025 at 12:20 PM Pratyush Yadav <pratyush@xxxxxxxxxx> wrote:
>
> On Thu, May 15 2025, Pasha Tatashin wrote:
>
> > Introduce a sysfs interface for the Live Update Orchestrator
> > under /sys/kernel/liveupdate/. This interface provides a way for
> > userspace tools and scripts to monitor the current state of the LUO
> > state machine.
>
> I am not sure if adding and maintaining a new UAPI that does the same
> thing is worth it. Can't we just have commandline utilities that can do
> the ioctls and fetch the LUO state, and those can be called from tools
> and scripts?
>

This is based on discussion from SystemD people. It is much simpler
for units to check the current 'state' via sysfs, and act accordingly.

> >
> > The main feature is a read-only file, state, which displays the
> > current LUO state as a string ("normal", "prepared", "frozen",
> > "updated"). The interface uses sysfs_notify to allow userspace
> > listeners (e.g., via poll) to be efficiently notified of state changes.
> >
> > ABI documentation for this new sysfs interface is added in
> > Documentation/ABI/testing/sysfs-kernel-liveupdate.
> >
> > This read-only sysfs interface complements the main ioctl interface
> > provided by /dev/liveupdate, which handles LUO control operations and
> > resource management.
> >
> > Signed-off-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
> [...]
>
> --
> Regards,
> Pratyush Yadav