[PATCH v3] liveupdate: add LUO_SESSION_MAGIC magic inode type

[Luca Boccassi]

On Fri, 17 Apr 2026 at 21:53, Pasha Tatashin <pasha.tatashin at soleen.com> wrote:
>
> On 04-17 21:40, luca.boccassi at gmail.com wrote:
> > From: Luca Boccassi <luca.boccassi at gmail.com>
> >
> > In userspace when managing LUO sessions we want to be able to identify
> > a FD as a LUO session, in order to be able to do the special handling
> > that they require in order to function as intended on kexec.
> >
> > Currently this requires scraping procfs and doing string matching on
> > the prefix of the dname, which is not an ideal interface.
> >
> > Add a singleton inode type with a magic value, so that we can
> > programmatically identify a fd as a LUO session via fstat().
> >
> > Signed-off-by: Luca Boccassi <luca.boccassi at gmail.com>
> > ---
> > This was requested by Lennart and Christian when discussing integration
> > with systemd for LUO management.
> >
> > v2: apply one fix from bot review about cleanup on error path:
> >     https://sashiko.dev/#/patchset/20260415184536.1155220-1-luca.boccassi%40gmail.com
> >     the other comments are invalid: luo is not a kmod, and the write hooks are not set up
> > v3: add test case to liveupdate selftest
>
> This should be split into two patches, also please CC:
> linux-kernel at vger.kernel.org

...

> Reverse-christmast-tree order please.

Done with v4, thanks