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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 13:24:48 -0700
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Sender: linux-nfs-owner@vger.kernel.org

linux-nfs-owner@vger.kernel.org wrote on 07/01/2016 01:07:42 PM:

> 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
> Sent by: linux-nfs-owner@vger.kernel.org
> 
> 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?

I am not sure what else systemctl will do but I need to control the order 
of the restart so the client will not see any errors.
I don't think that echo 0 > /proc/fs/nfsd/threads is freeing the lock, at 
least not the v3 locks, I will try again with v4.
The question is what is the most basic operation that can be done to start 
grace, will echo 8 > /proc/fs/nfsd/threads following echo 0 do it?
or is there any other primitive that will do it?
Marc.

> 
> --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.
> > 
> > 
> > 
> > 
> --
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