Subject: Re: [PATCH] [Bug 16494] NFS client over TCP hangs due to packet loss

From: Andy Chittenden <[email-masked]>
Date: Tue, 03 Aug 2010 11:25:30 +0100

On 2010-08-03 10:11, Andrew Morton wrote:
> (cc linux-nfs)
>
> On Tue, 03 Aug 2010 01:21:44 -0700 (PDT) David Miller<davem-fT/PcQaiUtIeIZ0/[email-masked]>  wrote:
>
>> From: "Andy Chittenden"<[email-masked]>
>> Date: Tue, 3 Aug 2010 09:14:31 +0100
>>
>>> I don't know whether this patch is the correct fix or not but it enables the
>>> NFS client to recover.
>>>
>>> Kernel version: 2.6.34.1 and 2.6.32.
>>>
>>> Fixes<https://bugzilla.kernel.org/show_bug.cgi?id=16494>. It clears down
>>> any previous shutdown attempts so that reconnects on a socket that's been
>>> shutdown leave the socket in a usable state (otherwise tcp_sendmsg() returns
>>> -EPIPE).
>>
>> If the SunRPC code wants to close a TCP socket then use it again,
>> it should disconnect by doing a connect() with sa_family == AF_UNSPEC

There is code to do that in the SunRPC code in xs_abort_connection() but 
that's conditionally called from xs_tcp_reuse_connection():

static void xs_tcp_reuse_connection(struct rpc_xprt *xprt, struct 
sock_xprt *transport)
{
	unsigned int state = transport->inet->sk_state;

	if (state == TCP_CLOSE && transport->sock->state == SS_UNCONNECTED)
		return;
	if ((1 << state) & (TCPF_ESTABLISHED|TCPF_SYN_SENT))
		return;
	xs_abort_connection(xprt, transport);
}

That's changed since 2.6.26 where it unconditionally did the connect() 
with sa_family == AF_UNSPEC. FWIW we cannot reproduce this problem with 
2.6.26.

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