netdev - Re: [PATCH] sunrpc: fix peername failed on closed listener

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Date:	Wed, 06 Jan 2010 17:07:32 +0800
From:	Xiaotian Feng <dfeng@...hat.com>
To:	"J. Bruce Fields" <bfields@...ldses.org>
CC:	linux-nfs@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Neil Brown <neilb@...e.de>,
	Trond Myklebust <Trond.Myklebust@...app.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] sunrpc: fix peername failed on closed listener

On 01/06/2010 07:01 AM, J. Bruce Fields wrote:
> On Thu, Dec 31, 2009 at 10:52:36AM +0800, Xiaotian Feng wrote:
>> There're some warnings of "nfsd: peername failed (err 107)!"
>> socket error -107 means Transport endpoint is not connected.
>> This warning message was outputed by svc_tcp_accept() [net/sunrpc/svcsock.c],
>> when kernel_getpeername returns -107. This means socket might be CLOSED.
>>
>> And svc_tcp_accept was called by svc_recv() [net/sunrpc/svc_xprt.c]
>>
>>          if (test_bit(XPT_LISTENER,&xprt->xpt_flags)) {
>>          <snip>
>>                  newxpt = xprt->xpt_ops->xpo_accept(xprt);
>>          <snip>
>>
>> So this might happen when xprt->xpt_flags has both XPT_LISTENER and XPT_CLOSE.
>>
>> Let's take a look at commit b0401d72, this commit has moved the close
>> processing after do recvfrom method, but this commit also introduces this
>> warnings, if the xpt_flags has both XPT_LISTENER and XPT_CLOSED, we should
>> close it, not accpet then close.
>
> The logic here seems unnecessarily complicated now, but as a minimal
> fix, this seems fine.
>
> Is the *only* justification for this to silence this warning, or is
> there some more serious problem I'm missing?

If a xprt->xpt_flags has XPT_CLOSE & XPT_LISTENER, kernel will accept it 
first,
and svc_xprt_received(xptr) no mater xpo_accept is suceed or failed, 
then svc_delete_xprt(xprt).

I'm not sure what will happened between the svc_xprt_received and 
svc_delete_xprt, there isn't any
lock to protect it.

>
> --b.
>
>>
>> Signed-off-by: Xiaotian Feng<dfeng@...hat.com>
>> Cc: J. Bruce Fields<bfields@...ldses.org>
>> Cc: Neil Brown<neilb@...e.de>
>> Cc: Trond Myklebust<Trond.Myklebust@...app.com>
>> Cc: David S. Miller<davem@...emloft.net>
>> ---
>> diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
>> index 1c924ee..187f0f4 100644
>> --- a/net/sunrpc/svc_xprt.c
>> +++ b/net/sunrpc/svc_xprt.c
>> @@ -699,7 +699,8 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
>>   	spin_unlock_bh(&pool->sp_lock);
>>
>>   	len = 0;
>> -	if (test_bit(XPT_LISTENER,&xprt->xpt_flags)) {
>> +	if (test_bit(XPT_LISTENER,&xprt->xpt_flags)&&
>> +	    !test_bit(XPT_CLOSE,&xprt->xpt_flags)) {
>>   		struct svc_xprt *newxpt;
>>   		newxpt = xprt->xpt_ops->xpo_accept(xprt);
>>   		if (newxpt) {
>

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