Re: kernel not recovering from statd port change

[Trond Myklebust <trond.myklebust@primarydata.com>]

On Thu, Aug 21, 2014 at 5:34 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
> While testing server restart somebody noticed that knfsd can't recover
> from statd restarting with a new port.
>
> From only a very quick skim of the code it looked like creating the nsm
> client with RPC_CLNT_CREATE_AUTOBIND should cause us to call rpcbind
> again on connection failures, but that doesn't seem to be working.
>
> Any ideas?  I'll keep looking....
>
> --b.
>
> commit 2c9fb5570fe2
> Author: J. Bruce Fields <bfields@redhat.com>
> Date:   Wed Aug 20 17:21:32 2014 -0400
>
>     lockd: allow rebinding to statd
>
>     During normal operation statd isn't restarted, but it may be if, for
>     example, the server is shut down and restarted to simulate a shutdown or
>     perform some kind of failover.  In that case the kernel may need to
>     query rpcbind again to get statd's new port number.
>
>     Symptoms were locking failures after a manual server restart (without
>     rebooting the machine), and loopback network traces showing the new
>     kernel nfsd attempting to contact statd at its old port number.
>
>     This was probably introduced by cb7323fffa85, which first allowed
>     reusing the statd rpc client, but it looks like a reference count may
>     typically have prevented any symptoms until e498daa81295 "LOCKD: Clear
>     ln->nsm_clnt only when ln->nsm_users is zero".
>
>     Fixes: cb7323fffa85 "lockd: create and use per-net NSM RPC clients on MON/UNMON requests"
>     Signed-off-by: J. Bruce Fields <bfields@redhat.com>
>
> diff --git a/fs/lockd/mon.c b/fs/lockd/mon.c
> index 1812f026960c..3bce1d318435 100644
> --- a/fs/lockd/mon.c
> +++ b/fs/lockd/mon.c
> @@ -80,7 +80,8 @@ static struct rpc_clnt *nsm_create(struct net *net)
>                 .program                = &nsm_program,
>                 .version                = NSM_VERSION,
>                 .authflavor             = RPC_AUTH_NULL,
> -               .flags                  = RPC_CLNT_CREATE_NOPING,
> +               .flags                  = RPC_CLNT_CREATE_NOPING|

RPC_CLNT_CREATE_HARDRTRY |

> +                                         RPC_CLNT_CREATE_AUTOBIND,
>         };
>
>         return rpc_create(&args);


-- 
Trond Myklebust

Linux NFS client maintainer, PrimaryData

trond.myklebust@primarydata.com