Date: Thu, 10 Aug 2017 09:51:26 -0600 From: Ian Lepore <ian@freebsd.org> To: Olavi Kumpulainen <olavi.m.kumpulainen@gmail.com>, freebsd-arm@freebsd.org Subject: Re: Question on mountd Message-ID: <1502380286.50720.97.camel@freebsd.org> In-Reply-To: <BB74132E-9F63-4DDB-9853-A8DAE3C28B64@gmail.com> References: <BB74132E-9F63-4DDB-9853-A8DAE3C28B64@gmail.com>
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On Thu, 2017-08-10 at 16:56 +0200, Olavi Kumpulainen wrote: > Hi guys, > > I notice that mount SIGHUP¢s mountd every time mount succeeds. The > SIGHUP causes mountd to remount all exported directories.If this > happens while a NFS-client is accessing a share, an access error may > occur. > For this purpose, there is an option to mount, -S, which locks nfsd > while the remount is executing. > > Can anyone of you share why mount needs to SIGHUP mountd in the first > place? It would make sense if mountd is restarted whenever > /etc/exports is modified, but always seems like overkill. > Based on looking through the mountd code a bit... When a new filesystem is mounted, it may be mounted on one of the mount points listed in /etc/exports. If there was no fs mounted there previously, then mountd might have failed to set the in-kernel export attributes the last time it processed the exports file, so it has to do the processing again after the mount to update the in-kernel export data. It would be really complex for mountd to try to figure out the minimal set of "what changed" after a mount succeeds, so it just completely reprocesses the exports file, first removing all export data from the kernel, then re- applying it all. So, all in all, I think the right fix for this is to add "mountd_flags="-r -S" to your rc.conf file (-r is a default from /etc/defaults/rc.conf). -- Ian
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