Date: Sun, 25 Oct 2020 21:35:09 +0000 From: Edward Tomasz Napierala <trasz@freebsd.org> To: Cy Schubert <Cy.Schubert@cschubert.com> Cc: 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: <20201025213509.GA1671@brick> In-Reply-To: <202010251417.09PEH6tE003403@slippy.cwsent.com> References: <202010251409.09PE91aS001781@repo.freebsd.org> <CAPjTQNEq2ukvkNoF6bsymTai52XV1tbu3TxW4rrN4n5hASMFqQ@mail.gmail.com> <202010251417.09PEH6tE003403@slippy.cwsent.com>
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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.
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