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To: Bruce Fields <bfields@fieldses.org>
Cc: linux-nfs@vger.kernel.org, "Tomer Perry" <TOMP@il.ibm.com>
Subject: Re: grace period
From: "Marc Eshel" <eshel@us.ibm.com>
Date: Fri, 1 Jul 2016 13:46:42 -0700
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This is my v3 test that show the lock still there after echo 0 > 
/proc/fs/nfsd/threads

[root@sonascl21 ~]# cat /etc/redhat-release 
Red Hat Enterprise Linux Server release 7.2 (Maipo)

[root@sonascl21 ~]# uname -a
Linux sonascl21.sonasad.almaden.ibm.com 3.10.0-327.el7.x86_64 #1 SMP Thu 
Oct 29 17:29:29 EDT 2015 x86_64 x86_64 x86_64 GNU/Linux

[root@sonascl21 ~]# cat /proc/locks | grep 999
3: POSIX  ADVISORY  WRITE 2349 00:2a:489486 0 999

[root@sonascl21 ~]# echo 0 > /proc/fs/nfsd/threads
[root@sonascl21 ~]# cat /proc/fs/nfsd/threads
0

[root@sonascl21 ~]# cat /proc/locks | grep 999
3: POSIX  ADVISORY  WRITE 2349 00:2a:489486 0 999


From:   Bruce Fields <bfields@fieldses.org>
To:     Marc Eshel/Almaden/IBM@IBMUS
Cc:     linux-nfs@vger.kernel.org
Date:   07/01/2016 01:07 PM
Subject:        Re: grace period


On Fri, Jul 01, 2016 at 10:31:55AM -0700, Marc Eshel wrote:
> It used to be that sending KILL signal to lockd would free locks and 
start 
> Grace period, and when setting nfsd threads to zero, nfsd_last_thread() 
> calls nfsd_shutdown that called lockd_down that I believe was causing 
both 
> freeing of locks and starting grace period or maybe it was setting it 
back 
> to a value > 0 that started the grace period.

OK, apologies, I didn't know (or forgot) that.

> Any way starting with the kernels that are in RHEL7.1 and up echo 0 > 
> /proc/fs/nfsd/threads doesn't do it anymore, I assume going to common 
> grace period for NLM and NFSv4 changed things.
> The question is how to do IP fail-over, so when a node fails and the IP 
is 
> moving to another node, we need to go into grace period on all the nodes 

> in the cluster so the locks of the failed node are not given to anyone 
> other than the client that is reclaiming his locks. Restarting NFS 
server 
> is to distractive.

What's the difference?  Just that clients don't have to reestablish tcp
connections?

--b.

> For NFSv3 KILL signal to lockd still works but for 
> NFSv4 have no way to do it for v4.
> Marc. 
> 
> 
> 
> From:   Bruce Fields <bfields@fieldses.org>
> To:     Marc Eshel/Almaden/IBM@IBMUS
> Cc:     linux-nfs@vger.kernel.org
> Date:   07/01/2016 09:09 AM
> Subject:        Re: grace period
> 
> 
> 
> On Thu, Jun 30, 2016 at 02:46:19PM -0700, Marc Eshel wrote:
> > I see that setting the number of nfsd threads to 0 (echo 0 > 
> > /proc/fs/nfsd/threads) is not releasing the locks and putting the 
server 
> 
> > in grace mode.
> 
> Writing 0 to /proc/fs/nfsd/threads shuts down knfsd.  So it should
> certainly drop locks.  If that's not happening, there's a bug, but we'd
> need to know more details (version numbers, etc.) to help.
> 
> That alone has never been enough to start a grace period--you'd have to
> start knfsd again to do that.
> 
> > What is the best way to go into grace period, in new version of the
> > kernel, without restarting the nfs server?
> 
> Restarting the nfs server is the only way.  That's true on older kernels
> true, as far as I know.  (OK, you can apparently make lockd do something
> like this with a signal, I don't know if that's used much, and I doubt
> it works outside an NFSv3-only environment.)
> 
> So if you want locks dropped and a new grace period, then you should run
> "systemctl restart nfs-server", or your distro's equivalent.
> 
> But you're probably doing something more complicated than that.  I'm not
> sure I understand the question....
> 
> --b.
> 
> 
> 
>