linux-kernel - Re: [PATCH v6 04/20] liveupdate: luo

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Message-ID: <CA+CK2bC1HviYczgs8=sh8Rt6rxgPgWuda4DGYpg+oLfHn5b2ow@mail.gmail.com>
Date: Mon, 17 Nov 2025 23:28:28 -0500
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: Mike Rapoport <rppt@...nel.org>
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Subject: Re: [PATCH v6 04/20] liveupdate: luo_session: add sessions support

On Mon, Nov 17, 2025 at 4:11 PM Mike Rapoport <rppt@...nel.org> wrote:
>
> On Mon, Nov 17, 2025 at 10:09:28AM -0500, Pasha Tatashin wrote:
> >
> > > > +     }
> > > > +
> > > > +     for (int i = 0; i < sh->header_ser->count; i++) {
> > > > +             struct luo_session *session;
> > > > +
> > > > +             session = luo_session_alloc(sh->ser[i].name);
> > > > +             if (IS_ERR(session)) {
> > > > +                     pr_warn("Failed to allocate session [%s] during deserialization %pe\n",
> > > > +                             sh->ser[i].name, session);
> > > > +                     return PTR_ERR(session);
> > > > +             }
> > >
> > > The allocated sessions still need to be freed if an insert fails ;-)
> >
> > No. We have failed to deserialize, so anyways the machine will need to
> > be rebooted by the user in order to release the preserved resources.
> >
> > This is something that Jason Gunthrope also mentioned regarding IOMMU:
> > if something is not correct (i.e., if a session cannot finish for some
> > reason), don't add complicated "undo" code that cleans up all
> > resources. Instead, treat them as a memory leak and allow a reboot to
> > perform the cleanup.
> >
> > While in this particular patch the clean-up looks simple, later in the
> > series we are adding file deserialization to each session to this
> > function. So, the clean-up will look like this: we would have to free
> > the resources for each session we deserialized, and also free the
> > resources for files that were deserialized for those sessions, only to
> > still boot into a "maintenance" mode where bunch of resources are not
> > accessible from which the machine would have to be rebooted to get
> > back to a normal state. This code will never be tested, and never be
> > used, so let's use reboot to solve this problem, where devices are
> > going to be properly reset, and memory is going to be properly freed.
>
> A part of this explanation should be a comment in the code.

Done.

>
> --
> Sincerely yours,
> Mike.