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From:   Olga Kornievskaia <olga.kornievskaia@gmail.com>
Date:   Sun, 28 Jun 2020 14:03:59 -0400
Message-ID: <CAN-5tyHuZwA-mrwUu1U+85-=mAFFtPZZJLAXyKyTaq7vqGwAfw@mail.gmail.com>
Subject: Re: [PATCH 1/1] SUNRPC dont update timeout value on connection reset
To:     Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna.schumaker@netapp.com>
Cc:     linux-nfs <linux-nfs@vger.kernel.org>
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Trond/Anna,

Any comments on this patch?

On Tue, Jun 23, 2020 at 11:22 AM Olga Kornievskaia
<olga.kornievskaia@gmail.com> wrote:
>
> Current behaviour: every time a v3 operation is re-sent to the server
> we update (double) the timeout. There is no distinction between whether
> or not the previous timer had expired before the re-sent happened.
>
> Here's the scenario:
> 1. Client sends a v3 operation
> 2. Server RST-s the connection (prior to the timeout) (eg., connection
> is immediately reset)
> 3. Client re-sends a v3 operation but the timeout is now 120sec.
>
> As a result, an application sees 2mins pause before a retry in case
> server again does not reply. Where as if a connection reset didn't
> change the timeout value, the client would have re-tried (the 3rd
> time) after 60secs.
>
> Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
>
> --- I have a question with regards to should we also not update the
> number of retries when connection is RST-ed? This would allow the
> client to still weather a 6mins (60+120+180) of unresponsive server.
> After this patch the client can handle only 3mins (60+120) of
> unresponsive server after the initial RST ---
> ---
>  net/sunrpc/clnt.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
> index a91d1cd..65517cf 100644
> --- a/net/sunrpc/clnt.c
> +++ b/net/sunrpc/clnt.c
> @@ -2405,7 +2405,8 @@ void rpc_force_rebind(struct rpc_clnt *clnt)
>                 goto out_exit;
>         }
>         task->tk_action = call_encode;
> -       rpc_check_timeout(task);
> +       if (status != -ECONNRESET && status != -ECONNABORTED)
> +               rpc_check_timeout(task);
>         return;
>  out_exit:
>         rpc_call_rpcerror(task, status);
> --
> 1.8.3.1
>