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Sun, 25 Oct 2020 14:45:59 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a25:d8d2:0:0:0:0:0 with HTTP; Sun, 25 Oct 2020 14:45:58 -0700 (PDT) In-Reply-To: <20201025213509.GA1671@brick> References: <202010251409.09PE91aS001781@repo.freebsd.org> <202010251417.09PEH6tE003403@slippy.cwsent.com> <20201025213509.GA1671@brick> From: Oliver Pinter Date: Sun, 25 Oct 2020 22:45:58 +0100 Message-ID: Subject: Re: svn commit: r367038 - head/sbin/mount_nullfs To: Cy Schubert , Oliver Pinter , "src-committers@freebsd.org" , "svn-src-all@freebsd.org" , "svn-src-head@freebsd.org" X-Rspamd-Queue-Id: 4CKBNm0xzCz4ZFR X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org; dkim=pass header.d=gmail.com header.s=20161025 header.b=b2tnNqcf; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (mx1.freebsd.org: domain of oliverpntr@gmail.com designates 2607:f8b0:4864:20::b31 as permitted sender) smtp.mailfrom=oliverpntr@gmail.com X-Spamd-Result: default: False [-2.97 / 15.00]; TO_DN_EQ_ADDR_SOME(0.00)[]; TO_DN_SOME(0.00)[]; R_SPF_ALLOW(-0.20)[+ip6:2607:f8b0:4000::/36:c]; FREEMAIL_FROM(0.00)[gmail.com]; RCPT_COUNT_FIVE(0.00)[5]; DKIM_TRACE(0.00)[gmail.com:+]; DMARC_POLICY_ALLOW(-0.50)[gmail.com,none]; FREEMAIL_TO(0.00)[cschubert.com,gmail.com,freebsd.org]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+,1:+,2:~]; FREEMAIL_ENVFROM(0.00)[gmail.com]; ASN(0.00)[asn:15169, ipnet:2607:f8b0::/32, country:US]; TAGGED_FROM(0.00)[]; DWL_DNSWL_NONE(0.00)[gmail.com:dkim]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-1.02)[-1.022]; R_DKIM_ALLOW(-0.20)[gmail.com:s=20161025]; FROM_HAS_DN(0.00)[]; NEURAL_SPAM_SHORT(0.05)[0.048]; NEURAL_HAM_LONG(-1.00)[-0.999]; TAGGED_RCPT(0.00)[]; MIME_GOOD(-0.10)[multipart/alternative,text/plain]; TO_MATCH_ENVRCPT_SOME(0.00)[]; RCVD_IN_DNSWL_NONE(0.00)[2607:f8b0:4864:20::b31:from]; RCVD_COUNT_TWO(0.00)[2]; RCVD_TLS_ALL(0.00)[]; MAILMAN_DEST(0.00)[svn-src-all,svn-src-head] Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.33 X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 25 Oct 2020 21:46:00 -0000 On Sunday, October 25, 2020, Edward Tomasz Napierala wrote: > On 1025T0717, Cy Schubert wrote: > > In message 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!