Re: rapid clustered nfs server failover and hung clients -- how best to close the sockets?

From: "J. Bruce Fields" <bfields@fieldses.org>
To: Jeff Layton <jlayton@redhat.com>
Cc: linux-nfs@vger.kernel.org, lhh@redhat.com, nfsv4@linux-nfs.org,
	nhorman@redhat.com
Subject: Re: rapid clustered nfs server failover and hung clients -- how best to close the sockets?
Date: Mon, 9 Jun 2008 11:51:36 -0400	[thread overview]
Message-ID: <20080609155136.GC25230@fieldses.org> (raw)
In-Reply-To: <20080609103137.2474aabd@tleilax.poochiereds.net>

On Mon, Jun 09, 2008 at 10:31:37AM -0400, Jeff Layton wrote:
> I can think of 3 ways to fix this:
> 
> 1) Add something like the recently added "unlock_ip" interface that
> was added for NLM. Maybe a "close_ip" that allows us to close all
> nfsd sockets connected to a given local IP address. So clustering
> software could do something like:
> 
>     # echo 10.20.30.40 > /proc/fs/nfsd/close_ip
> 
> ...and make sure that all of the sockets are closed.
> 
> 2) just use the same "unlock_ip" interface and just have it also
> close sockets in addition to dropping locks.
> 
> 3) have an nfsd close all non-listening connections when it gets a
> certain signal (maybe SIGUSR1 or something). Connections on a
> sockets that aren't failing over should just get a RST and would
> reopen their connections.
> 
> ...my preference would probably be approach #1.

What do you see as the advantage of #1 over #2?  Are there cases where
someone would want to drop locks but not also close connections (or
vice-versa)?

--b.
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