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

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Message-ID: <20231011163220.GA1970@templeofstupid.com>
Date:   Wed, 11 Oct 2023 09:32:20 -0700
From:   Krister Johansen <kjlx@...pleofstupid.com>
To:     Miklos Szeredi <miklos@...redi.hu>
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, Oct 11, 2023 at 09:07:33AM +0200, Miklos Szeredi wrote:
> 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.

That seems possible.  Would the idea be to move all tracking of nlookup
to a separate refcounted object for the particular nodeid, or just do
this for the first lookup of a submount?

Would you like me to put together a v3 that heads this direction?

Thanks,

-K