linux-kernel - Re: [resend PATCH v2 2/2] fuse: ensure that submounts lookup their parent

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Message-ID: <CAJfpegukL5bj6U0Kvvw_uTW1jstoD2DTLM7kByx2HAhOP02HEg@mail.gmail.com>
Date:   Wed, 11 Oct 2023 09:07:33 +0200
From:   Miklos Szeredi <miklos@...redi.hu>
To:     Krister Johansen <kjlx@...pleofstupid.com>
Cc:     linux-fsdevel@...r.kernel.org,
        Miklos Szeredi <mszeredi@...hat.com>,
        linux-kernel@...r.kernel.org,
        German Maglione <gmaglione@...hat.com>,
        Greg Kurz <groug@...d.org>, Max Reitz <mreitz@...hat.com>,
        Bernd Schubert <bernd.schubert@...tmail.fm>
Subject: Re: [resend PATCH v2 2/2] fuse: ensure that submounts lookup their parent

On Wed, 11 Oct 2023 at 03:26, Krister Johansen <kjlx@...pleofstupid.com> wrote:

> I am curious what you have in mind in order to move this towards a
> proper fix?  I shied away from the approach of stealing a nlookup from
> mp_fi beacuse it wasn't clear that I could always count on the nlookup
> in the parent staying positive.  E.g. I was afraid I was either going to
> not have enough nlookups to move to submounts, or trigger a forget from
> an exiting container that leads to an EBADF from the initial mount
> namespace.

One idea is to transfer the nlookup to a separately refcounted object
that is referenced from mp_fi as well as all the submounts.

Thanks,
Miklos