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Date:      Sun, 25 Oct 2020 22:45:58 +0100
From:      Oliver Pinter <oliver.pntr@gmail.com>
To:        Cy Schubert <Cy.Schubert@cschubert.com>, Oliver Pinter <oliver.pntr@gmail.com>,  "src-committers@freebsd.org" <src-committers@freebsd.org>,  "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>,  "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>
Subject:   Re: svn commit: r367038 - head/sbin/mount_nullfs
Message-ID:  <CAPjTQNG-FWA4ycviJjL7jeFBKv-CMS8HQpdvxwGazZ8jU=vnzg@mail.gmail.com>
In-Reply-To: <20201025213509.GA1671@brick>
References:  <202010251409.09PE91aS001781@repo.freebsd.org> <CAPjTQNEq2ukvkNoF6bsymTai52XV1tbu3TxW4rrN4n5hASMFqQ@mail.gmail.com> <202010251417.09PEH6tE003403@slippy.cwsent.com> <20201025213509.GA1671@brick>

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On Sunday, October 25, 2020, Edward Tomasz Napierala <trasz@freebsd.org>
wrote:

> On 1025T0717, Cy Schubert wrote:
> > In message <CAPjTQNEq2ukvkNoF6bsymTai52XV1tbu3TxW4rrN4n5hASMFqQ@mail.
> gmail.c
> > om>
> > , Oliver Pinter writes:
> > > On Sunday, October 25, 2020, Edward Tomasz Napierala <
> trasz@freebsd.org>
> > > wrote:
> > >
> > > > Author: trasz
> > > > Date: Sun Oct 25 14:09:00 2020
> > > > New Revision: 367038
> > > > URL: https://svnweb.freebsd.org/changeset/base/367038
> > > >
> > > > Log:
> > > >   Remove the check that prevents creating "loops" from
> mount_nullfs(8).
> > > >
> > > >
> > > The simple question is: why?
> >
> > I was about to ask that myself.
> >
> > The why is usually more important than the how.
>
> Two reasons.
>
> First, from what I can tell this is an artificial limitation which serves
> no purpose.  I thought it was to prevent some kind of deadlock between
> vnodes, so I asked kib@, and he mentioned removing that very limitation
> from the kernel code; thus, it looks to me like a historical leftover.
>
> Second, I've stumbled upon this when trying to nullfs-mount '/' on
> '/compat/ubuntu/bsd/', which would be useful for autochroot functionality,
> when (or if) it becomes a thing.


Thank you!



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