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

[Rick Macklem]

Alan Somers wrote:
>Will a restart of the daemon cause clients to get HUPped if they try
>to access an exported filesystem while mountd is restarting?
>-Alan
I'm not sure what you mean by HUPped, but during a restart of mountd, extant
mounts should continue to work.

What will fail during the mountd restart is new NFSv3 mount attempts, because
they won't be able to talk to mountd via the Mount protocol. Usually the
failure will be rpcbind not having MOUNTPROG registered.
Then a retry of the mount (which will happen after something like 30sec if you
don't <ctrl>C the mount command) will succeed, assuming mountd has restarted.
Unmounts will complain the MOUNTPROG wasn't registered, but the umount
will work anyhow.

Then "showmount", which is never guaranteed to return correct info, will report it
as still mounted. Since "showmount" never knows about NFSv4 mounts and just
returns its guess at what is mounted, I don't find it useful anyhow.

 NFSv4 mounts should continue to work when mountd isn't running, since they don't use the Mount protocol. And, since they don't use the Mount protocol, "showmount"
never knows about them.

So, I restart can cause some disruption, but they are mostly just delays when doing
new NFSv3 mounts on the server.

rick

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
>
[stuff snipped]