RFC: should an incremental reload of exports for mountd be optional?

[Alan Somers]

Will a restart of the daemon cause clients to get HUPped if they try
to access an exported filesystem while mountd is restarting?
-Alan

On Mon, Jun 3, 2019 at 5:13 PM Rick Macklem <rmacklem at uoguelph.ca> wrote:
>
> Thanks everyone for your comments. I just committed the patch with
> the incremental reload of exports always enabled.
> If people run into problems, I can add some "backdoor" way to disable
> it, as suggested by asomers at .
>
> A restart of the daemon will always do a full reload to work around any
> reload failures.
>
> rick
>
> ________________________________________
> From: Alan Somers <asomers at freebsd.org>
> Sent: Monday, June 3, 2019 6:28:51 PM
> To: Peter Eriksson
> Cc: Rick Macklem; freebsd-fs at freebsd.org
> Subject: Re: RFC: should an incremental reload of exports for mountd be optional?
>
> I think that it should be always enabled.  If the only reason not to
> is a fear of bugs in the new method, then the old method can be
> selected by some back-doorish workaround, like an environment
> variable.
> -Alan
>
> On Mon, Jun 3, 2019 at 4:16 PM Peter Eriksson <pen at lysator.liu.se> wrote:
> >
> > My vote goes to:
> >
> > Enabled by default (with an option to disable it in case problems pop up).
> >
> > - Peter
> >
> >
> > > On 31 May 2019, at 23:50, Rick Macklem <rmacklem at uoguelph.ca> wrote:
> > >
> > > Hi,
> > >
> > > I have created a patch for PR#237860 that improves the time it takes to reload
> > > the exports file(s) for an NFS file server from seconds->milliseconds by only doing
> > > system calls for the changes to the exports file(s). (Assumes each reload includes
> > > changes to only a small fraction of the entries.)
> > >
> > > I made it a non-default option of "-I", but asomers@ asked why it needed to be
> > > optional.
> > >
> > > Basically, I made it optional because I felt the patch might still be buggy and not
> > > handle some case of an exports file change that I missed.
> > >
> > > However, I can see the argument of making it non-optional (or optional but enabled
> > > by default) so that sysadmins don't need to add "-I" to avoid long periods where the
> > > nfsd threads are suspended.
> > > If it is broken, the deamon would need to be restarted to do a full reload, but that
> > > would also be the case if a sysadmin specified the "-I" option.
> > >
> > > So, the question is... "do you think this should be an option or just always enabled?".
> > >
> > > Thanks , rick
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