[PATCH v1 1/7] liveupdate: Add LIVEUPDATE_SESSION_FREEZE ioctl to freeze sessions early

[sashiko-bot at kernel.org]

> Currently, LUO sessions are frozen automatically only inside the
> reboot(LINUX_REBOOT_CMD_KEXEC) pathway, where luo_session_serialize()
> iterates through all outgoing sessions under global write locks and
> freezes them serially during shutdown. Allowing userspace to decide when
> to freeze a session once it is done with it (and to freeze multiple
> sessions in parallel, since luo_session_freeze() only acquires the
> per-session mutex) avoids postponing this work to kexec shutdown and
> reduces blackout time.
> 
> Introduce LIVEUPDATE_SESSION_FREEZE on session file descriptors to freeze
> a session early. The ioctl runs .freeze() across all preserved files in the
> session and serializes their metadata. Once frozen, no additional files can
> be added to the session, and subsequent freeze calls return -EBUSY. Freeze
> is only valid on outgoing sessions and returns -EINVAL on incoming ones.
> 
> During kexec, sessions that were already frozen early are skipped, while
> sessions that did not invoke this ioctl auto-freeze as before. If an
> early-frozen session is released before kexec, its files are rolled back
> via .unfreeze() before being unpreserved.
> 
> Signed-off-by: Pasha Tatashin <pasha.tatashin at soleen.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20261015093816.2438942-1-pasha.tatashin@soleen.com?part=1