Re: [PATCH 1/2] NFSv4.1: Handle NFS4ERR_BADSESSION/NFS4ERR_DEADSESSION replies to OP_SEQUENCE

[Olga Kornievskaia <aglo@umich.edu>]

On Sun, Dec 4, 2016 at 7:40 PM, Trond Myklebust
<trond.myklebust@primarydata.com> wrote:
> In the case where SEQUENCE receives a NFS4ERR_BADSESSION or
> NFS4ERR_DEADSESSION error, we just want to report the session as needing
> recovery, and then we want to retry the operation.
>
> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
> ---
>  fs/nfs/nfs4proc.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index f992281c9b29..4fd0e2b7b08e 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -816,6 +816,10 @@ static int nfs41_sequence_process(struct rpc_task *task,
>         case -NFS4ERR_SEQ_FALSE_RETRY:
>                 ++slot->seq_nr;
>                 goto retry_nowait;
> +       case -NFS4ERR_DEADSESSION:
> +       case -NFS4ERR_BADSESSION:
> +               nfs4_schedule_session_recovery(session, res->sr_status);
> +               goto retry_nowait;
>         default:
>                 /* Just update the slot sequence no. */
>                 slot->seq_done = 1;
> --
> 2.9.3

Hi Trond,

Can you explain the implications of retrying the operation without
waiting for recovery to complete?

This patch introduces regression in intra COPY failing if the server
rebooted during that operation. What happens is that COPY is re-sent
with the same stateid from the old open instead of the open that was
done from the recovery (leading to BAD_STATEID error and failure).

I wonder if it's because COPY is written to just use nfs4_call_sync()
instead of defining rpc_callback_ops to handle rpc_prepare() where a
new stateid could be gotten? I have re-written the COPY to do that and
I no longer see that problem.

If my suspicion is correct, it would help for the future to know that
any operations that use stateid must have rpc callback ops
defined/used so that they avoid this problem. Perhaps as a comment in
the code or maybe some other way?

Thanks.