Re: [PATCH] nfsd4: handle failure to find backchannel

[Kinglong Mee <kinglongmee@gmail.com>]

On 7/17/2014 23:13, J. Bruce Fields wrote:
> On Thu, Jul 17, 2014 at 09:24:13PM +0800, Kinglong Mee wrote:
>> On 7/17/2014 06:05, J. Bruce Fields wrote:
>>> On Sat, Jul 12, 2014 at 10:02:17PM +0800, Kinglong Mee wrote:
>>>> On 7/12/2014 05:16, J. Bruce Fields wrote:
>>>>> The local variable "ses" will be left NULL here in the case we fail to
>>>>> find a connection.  Spotted by a coverity scan.
>>>>>     
>>>>> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
>>>>>
>>>>> diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
>>>>> index 2c73cae9899d..fe22cd5c42d3 100644
>>>>> --- a/fs/nfsd/nfs4callback.c
>>>>> +++ b/fs/nfsd/nfs4callback.c
>>>>> @@ -1001,14 +1001,18 @@ static void nfsd4_process_cb_update(struct nfsd4_callback *cb)
>>>>>  	}
>>>>>  	spin_unlock(&clp->cl_lock);
>>>>>  
>>>>> +	if (!c)
>>>>> +		goto out_no_connection;
>>>>
>>>> Setting err to -EINVAL maybe better.
>>>> Otherwise, nfsd4_mark_cb_down will be called with err == 0.
>>>>
>>>>>  	err = setup_callback_client(clp, &conn, ses);
>>>>
>>>> setup_callback_client also return -EINVAL when ses == NULL with conn.cb_xprt == NULL.
>>>
>>> Thanks, yes, after looking over this carefully I don't believe we can
>>> call setup_callback_client with ses NULL but conn->cb_xprt non-NULL, so
>>> this is just a false positive from coverity.
>>
>> ses and conn->cb_xprt will be set in the same condition before
>> calling setup_callback_client,
>>
>>  996         c = __nfsd4_find_backchannel(clp);
>>  997         if (c) {
>>  998                 svc_xprt_get(c->cn_xprt);
>>  999                 conn.cb_xprt = c->cn_xprt;
>> 1000                 ses = c->cn_session;
>> 1001         }
>> 1002         spin_unlock(&clp->cl_lock);
>> 1003
>> 1004         err = setup_callback_client(clp, &conn, ses);
>>
>> ses and conn->cb_xprt will be NULL or non-NULL in the same time,
>> so that, call setup_calback_client with ses NULL but conn->cb_xprt non-NULL will not appear.
> 
> Agreed but you also need to check what happens in the case where c is
> NULL.
> 
> This is much more confusing than necessary.  But I'm inclined to hold
> off on any cleanup here while jlayton's patches are still pending.

Got it.
I also have some cleanup, will send after jlayton's patches merged.

thanks,
Kinglong Mee

> 
> --b.
> 
>>
>> thanks,
>> Kinglong Mee
>>
>>>>> -	if (err) {
>>>>> -		nfsd4_mark_cb_down(clp, err);
>>>>> -		return;
>>>>> -	}
>>>>> +	if (err)
>>>>> +		goto out_no_connection;
>>>>>  	/* Yay, the callback channel's back! Restart any callbacks: */
>>>>>  	list_for_each_entry(cb, &clp->cl_callbacks, cb_per_client)
>>>>>  		run_nfsd4_cb(cb);
>>>>> +	return;
>>>>> +out_no_connection:
>>>>> +	nfsd4_mark_cb_down(clp, err);
>>>>> +	return;
>>>>>  }
>>>>>  
>>>>>  static void nfsd4_do_callback_rpc(struct work_struct *w)
>>>>> --
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>>>
>