Re: grace period

[Bruce Fields <bfields@fieldses.org>]

On Fri, Jul 01, 2016 at 01:46:42PM -0700, Marc Eshel wrote:
> 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

Huh, that's not what I see.  Are you positive that's the lock on the
backend filesystem and not the client-side lock (in case you're doing a
loopback mount?)

--b.

> 
> 
> 
> 
> 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.
> > 
> > 
> > 
> > 
> 
> 
> 
>