Re: [PATCH 1/2] SUNRPC: Ensure that call_connect times out correctly

[Steve Dickson <SteveD@redhat.com>]

On 03/18/2014 02:45 PM, Trond Myklebust wrote:
> On Tue, 2014-03-18 at 13:24 -0400, Steve Dickson wrote:
>>
>> On 03/18/2014 11:58 AM, Trond Myklebust wrote:
>>>
>>> On Mar 18, 2014, at 11:47, Steve Dickson <SteveD@redhat.com> wrote:
>>>
>>>> Hey,
>>>>
>>>> On 03/17/2014 02:40 PM, Trond Myklebust wrote:
>>>>> When the server is unavailable due to a networking error, etc, we want
>>>>> the RPC client to respect the timeout delays when attempting to reconnect.
>>>>>
>>>>> Fixes: 561ec1603171 (SUNRPC: call_connect_status should recheck bind..)
>>>>> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
>>>>> ---
>>>>> net/sunrpc/clnt.c | 8 +++-----
>>>>> 1 file changed, 3 insertions(+), 5 deletions(-)
>>>>>
>>>>> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
>>>>> index 0edada973434..f22d3a115fda 100644
>>>>> --- a/net/sunrpc/clnt.c
>>>>> +++ b/net/sunrpc/clnt.c
>>>>> @@ -1798,10 +1798,6 @@ call_connect_status(struct rpc_task *task)
>>>>> 	trace_rpc_connect_status(task, status);
>>>>> 	task->tk_status = 0;
>>>>> 	switch (status) {
>>>>> -		/* if soft mounted, test if we've timed out */
>>>>> -	case -ETIMEDOUT:
>>>>> -		task->tk_action = call_timeout;
>>>>> -		return;
>>>>> 	case -ECONNREFUSED:
>>>>> 	case -ECONNRESET:
>>>>> 	case -ECONNABORTED:
>>>>> @@ -1812,7 +1808,9 @@ call_connect_status(struct rpc_task *task)
>>>>> 		if (RPC_IS_SOFTCONN(task))
>>>>> 			break;
>>>>> 	case -EAGAIN:
>>>>> -		task->tk_action = call_bind;
>>>>> +	case -ETIMEDOUT:
>>>>> +		/* Check if we've timed out before looping back to call_bind */
>>>>> +		task->tk_action = call_timeout;
>>>>> 		return;
>>>>> 	case 0:
>>>>> 		clnt->cl_stats->netreconn++;
>>>>>
>>>> How is this support to work if the trunking code still ignores timeouts? 
>>>>
>>>> [ 2076.045176] NFS: nfs4_discover_server_trunking after status -110, retrying
>>>
>>> The above patch fixes the regression that Neil tracked down in Linux 3.12, and that 
>>> affects the generic RPC handling of soft timeouts.
>>>
>>> The trunking code's handling of ETIMEDOUT has been there since Linux 3.7 
>>> and hasn’t changed, so I really don’t see how it can have worked at one time before 3.12.
>> Maybe it been broken that long.... :-) 
>>
>> But here is the obvious loop that stop that hangs a mount forever:
>>
>>  #8 [ffff88007a22b7e8] rpc_call_sync at ffffffffa0220210 [sunrpc]
>>  #9 [ffff88007a22b840] nfs4_proc_setclientid at ffffffffa0505c49 [nfsv4]
>> #10 [ffff88007a22b988] nfs40_discover_server_trunking at ffffffffa0514489 [nfsv4]
>> #11 [ffff88007a22b9d0] nfs4_discover_server_trunking at ffffffffa0516f2d [nfsv4]
>> #12 [ffff88007a22ba28] nfs4_init_client at ffffffffa051e9a4 [nfsv4]
>> #13 [ffff88007a22bb20] nfs_get_client at ffffffffa04bd6ba [nfs]
>> #14 [ffff88007a22bb80] nfs4_set_client at ffffffffa051dfb0 [nfsv4]
>> #15 [ffff88007a22bc00] nfs4_create_server at ffffffffa051f4ce [nfsv4]
>> #16 [ffff88007a22bc88] nfs4_remote_mount at ffffffffa051790e [nfsv4]
>> #17 [ffff88007a22bcb0] mount_fs at ffffffff811b3dd9
>>
>> The SETCLIENT times out 
>>    NFS call  setclientid auth=UNIX, 'Linux NFSv4.0 10.19.60.77/10.19.60.33 tcp'
>>    NFS reply setclientid: -110
>>
>> The nfs4_discover_server_trunking() retries 
>>    NFS: nfs4_discover_server_trunking after status -110, retrying
>>
>> The happens when there server is down and so the connections 
>> fail with ECONNREFUSED:
>>    RPC:     2 call_connect_status (status -111)
>>
>> The mount system call never times out in which it did in the past. 
> 
> Why should a mount system call time out other than perhaps in the case
> of a soft mount?
> 
So the mount can go in background. As you know the -o bg is used in
the /etc/fstab so the boot does not get hung up with downed servers. 
That's how it always worked... 

steved.