Re: [PATCH 1/8] nfsd: don't restart v4.1+ callback when RPC_SIGNALLED is set

NeilBrown
2025-01-25T23:01:51Z

On Fri, 24 Jan 2025, Jeff Layton wrote:
> This is problematic, since the RPC might have been entirely successful.
> There is no point in restarting a v4.1+ callback just because
> RPC_SIGNALLED is true. The v4.1+ error handling has other mechanisms for
> detecting when it should retransmit the RPC.

But why might RPC_SIGNALLED() ever be true?
The flag RPC_TASK_SIGNALLED is only ever set by rpc_signal_task() which
is only called from rpc_killall_tasks() and __rpc_execute() for
non-async tasks which doesn't apply to nfsd callbacks as they are
started with rpc_call_async().

rpc_killall_tasks() is called by fs/nfs/ which isn't relevant for us,
and from rpc_shutdown_client(). In those cases we certainly don't want
the request to be retried, though the nfsd4_process_cb_update() case is
a little interesting as we do want it to be retried, but in a different
client.

So the code you are removing is either dead code because something else
will prevent the restart when a client is being shut down, or it is bad
code because it would delay rpc_shutdown_client() while the request is
retried.

I haven't dug the extra step to figure out which, but either way I think
the code should go.

NeilBrown

>
> Fixes: 7ba6cad6c88f ("nfsd: New helper nfsd4_cb_sequence_done() for processing more cb errors")
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
> fs/nfsd/nfs4callback.c | 3 ---
> 1 file changed, 3 deletions(-)
>
> diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
> index 50e468bdb8d4838b5217346dcc2bd0fec1765c1a..e12205ef16ca932ffbcc86d67b0817aec2436c89 100644
> --- a/fs/nfsd/nfs4callback.c
> +++ b/fs/nfsd/nfs4callback.c
> @@ -1403,9 +1403,6 @@ static bool nfsd4_cb_sequence_done(struct rpc_task *task, struct nfsd4_callback
> }
> trace_nfsd_cb_free_slot(task, cb);
> nfsd41_cb_release_slot(cb);
> -
> - if (RPC_SIGNALLED(task))
> - goto need_restart;
> out:
> return ret;
> retry_nowait:
>
> --
> 2.48.1
>
>