Date: Tue, 7 Nov 2017 08:21:54 -0700 From: Alan Somers <asomers@freebsd.org> To: Edward Tomasz Napierala <trasz@freebsd.org> Cc: "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: r325392 - head/etc/autofs Message-ID: <CAOtMX2izYct6ToUGwNA=0wzZT7ir6HpPUOt_AkuhfvORmQ4=QQ@mail.gmail.com> In-Reply-To: <201711041438.vA4Ec0vx097305@repo.freebsd.org> References: <201711041438.vA4Ec0vx097305@repo.freebsd.org>
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On Sat, Nov 4, 2017 at 8:38 AM, Edward Tomasz Napierala <trasz@freebsd.org> wrote: > Author: trasz > Date: Sat Nov 4 14:38:00 2017 > New Revision: 325392 > URL: https://svnweb.freebsd.org/changeset/base/325392 > > Log: > Add NIS automounter map, which supports rewriting of self-hosted locations > to make them nullfs. > > PR: 221010 > Submitted by: G. Paul Ziemba > MFC after: 2 weeks This is not generally safe with NFSv4. If vfs.nfsd.issue_delegations==1, then the server will allow NFS clients to delay flushing writes back to the server. The protocol handles multiple clients that want delegations for the same file, but it doesn't handle local access. So if somebody tries to automount a locally-hosted NFSv4 volume with delegations enabled, but accidentally mounts it with nullfs instead, file corruption could result. The simplest solution would be to never use nullfs if vfs.nfsd.issue_delgations==1. -Alan
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