Re: [PATCH 13/20] NFS: Fix recovery from NFS4ERR_CLID_INUSE

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On Thu, 2012-04-26 at 14:53 -0400, Trond Myklebust wrote:
> On Thu, 2012-04-26 at 14:43 -0400, Chuck Lever wrote:
> > On Apr 26, 2012, at 12:55 PM, Myklebust, Trond wrote:
> > 
> > > On Thu, 2012-04-26 at 12:24 -0400, Chuck Lever wrote:
> > >> On Apr 23, 2012, at 4:55 PM, Chuck Lever wrote:
> > > Then lets move the flavour out of the clientid string,
> > 
> > Removing the flavor from the nfs_client_id4 string makes sense.
> > 
> > > and just settle
> > > for handling CLID_INUSE by changing the flavour on the SETCLIENTID call.
> > 
> > This is where I get hazy.  
> > 
> > If I simply change the authentication flavor on the existing clp->cl_rpcclient, will this affect ongoing RENEW operations that also use this transport?  Do we want subsequent RENEW operations to use the new flavor?
> > 
> > Thinking hypothetically, it seems to me that CLID_INUSE is really an indication of a permanent configuration error, or a software bug, and we should not bother to recover.  But maybe that's my limited imagination.  Under what use cases do you think CLID_INUSE might occur and it might be useful to attempt recovery?
> > 
> The server caches the principal name that was used to call SETCLIENTID
> when the lease was established. Any attempt to call SETCLIENTID with a
> different principal will result in CLID_INUSE unless the lease has
> expired.
> So what I was proposing wasn't that you try to change the authentication
> flavour on an existing nfs_client. It was that when you are probing, you
> can use the CLID_INUSE reply from SETCLIENTID as a direct indication
> that the server is indeed trunked, and that you already hold a lease on
> that server, but that the authentication flavour that you are trying to
> use is wrong.

Actually, let me qualify that a bit. CLID_INUSE can also mean one other
thing: that you have previously established a lease on that server, with
a different authentication flavour, and that lease has not yet expired
(even though your client may have forgotten it due to a umount of all
filesystems from that server).

Trond Myklebust
Linux NFS client maintainer


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