linux-kernel - Re: [PATCH v4 14/30] liveupdate: luo_session: Add ioctls for file preservation and state management

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Message-ID: <CA+CK2bDUDryK6xZt5u-cMv+eR8ZWC82Phu9F2fS8DMnac5ritg@mail.gmail.com>
Date: Wed, 29 Oct 2025 17:17:35 -0400
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: David Matlack <dmatlack@...gle.com>
Cc: Pratyush Yadav <pratyush@...nel.org>, jasonmiu@...gle.com, graf@...zon.com, 
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Subject: Re: [PATCH v4 14/30] liveupdate: luo_session: Add ioctls for file
 preservation and state management

On Wed, Oct 29, 2025 at 5:13 PM David Matlack <dmatlack@...gle.com> wrote:
>
> On Wed, Oct 29, 2025 at 1:13 PM Pasha Tatashin
> <pasha.tatashin@...een.com> wrote:
>
> > Simplified uAPI Proposal
> > The simplest uAPI would look like this:
> > IOCTLs on /dev/liveupdate (to create and retrieve session FDs):
> > LIVEUPDATE_IOCTL_CREATE_SESSION
> > LIVEUPDATE_IOCTL_RETRIEVE_SESSION
>
> > - If everything succeeds, the session becomes an empty "outgoing"
> > session. It can then be closed and discarded or reused for the next
> > live update by preserving new FDs into it.
>
> I think it would be useful to cleanly separate incoming and outgoing
> sessions. The only way to get an outgoing session is with
> LIVEUPDATE_IOCTL_CREATE_SESSION. Incoming sessions can be retrieved
> with LIVEUPDATE_IOCTL_RETRIEVE_SESSION.
>
> It is fine and expected for incoming and outgoing sessions to have the
> same name. But they are different sessions. This way, the kernel can
> easily keep track of incoming and outgoing sessions separately, and
> there is not need to "transition" and session from incoming to
> outgoing.

Yes, good idea, I was thinking of recycling finished and empty
sessions, but it will only add complications.

Pasha