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Date:   Mon, 27 Mar 2023 09:05:09 -0700
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Subject: Re: Fwd: [PATCH] SUNRPC: remove the maximum number of retries in
 call_bind_status
Content-Language: en-US
To:     Chuck Lever III <chuck.lever@oracle.com>,
        Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna@kernel.org>
Cc:     Helen Chao <helen.chao@oracle.com>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
References: <ed870a33-0809-3cfd-2d5a-b97409568b97@oracle.com>
 <ACE2DBA2-0F3D-47EF-9167-9D45F5BE57E5@oracle.com>
From:   dai.ngo@oracle.com
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Hi,

Just a friendly reminder for the status of this patch.

Thanks,

-Dai

On 3/16/23 6:38 AM, Chuck Lever III wrote:
> We need to hear from the NFS client maintainers about
> the below question and the patch.
>
>
>> Begin forwarded message:
>>
>> From: dai.ngo@oracle.com
>> Subject: Re: [PATCH] SUNRPC: remove the maximum number of retries in call_bind_status
>> Date: March 14, 2023 at 12:19:30 PM EDT
>> To: Chuck Lever III <chuck.lever@oracle.com>
>> Cc: Linux NFS Mailing List <linux-nfs@vger.kernel.org>, Helen Chao <helen.chao@oracle.com>
>>
>>
>> On 3/8/23 11:03 AM, dai.ngo@oracle.com wrote:
>>> On 3/8/23 10:50 AM, Chuck Lever III wrote:
>>>>> On Mar 8, 2023, at 1:45 PM, Dai Ngo <dai.ngo@oracle.com> wrote:
>>>>>
>>>>> Currently call_bind_status places a hard limit of 3 to the number of
>>>>> retries on EACCES error. This limit was done to accommodate the behavior
>>>>> of a buggy server that keeps returning garbage when the NLM daemon is
>>>>> killed on the NFS server. However this change causes problem for other
>>>>> servers that take a little longer than 9 seconds for the port mapper to
>>>>> become ready when the NFS server is restarted.
>>>>>
>>>>> This patch removes this hard coded limit and let the RPC handles
>>>>> the retry according to whether the export is soft or hard mounted.
>>>>>
>>>>> To avoid the hang with buggy server, the client can use soft mount for
>>>>> the export.
>>>>>
>>>>> Fixes: 0b760113a3a1 ("NLM: Don't hang forever on NLM unlock requests")
>>>>> Reported-by: Helen Chao <helen.chao@oracle.com>
>>>>> Tested-by: Helen Chao <helen.chao@oracle.com>
>>>>> Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
>>>> Helen is the royal queen of ^C  ;-)
>>>>
>>>> Did you try ^C on a mount while it waits for a rebind?
>>> She uses a test script that restarts the NFS server while NLM lock test
>>> is running. The failure is random, sometimes it fails and sometimes it
>>> passes depending on when the LOCK/UNLOCK requests come in so I think
>>> it's hard to time it to do the ^C, but I will ask.
>> We did the test with ^C and here is what we found.
>>
>> For synchronous RPC task the signal was delivered to the RPC task and
>> the task exit with -ERESTARTSYS from __rpc_execute as expected.
>>
>> For asynchronous RPC task the process that invokes the RPC task to send
>> the request detected the signal in rpc_wait_for_completion_task and exits
>> with -ERESTARTSYS. However the async RPC was allowed to continue to run
>> to completion. So if the async RPC task was retrying an operation and
>> the NFS server was down, it will retry forever if this is a hard mount
>> or until the NFS server comes back up.
>>
>> The question for the list is should we propagate the signal to the async
>> task via rpc_signal_task to stop its execution or just leave it alone as is.
>>
>> -Dai
>>
>>> Thanks,
>>> -Dai
>>>
>>>>
>>>>> ---
>>>>> include/linux/sunrpc/sched.h | 3 +--
>>>>> net/sunrpc/clnt.c            | 3 ---
>>>>> net/sunrpc/sched.c           | 1 -
>>>>> 3 files changed, 1 insertion(+), 6 deletions(-)
>>>>>
>>>>> diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h
>>>>> index b8ca3ecaf8d7..8ada7dc802d3 100644
>>>>> --- a/include/linux/sunrpc/sched.h
>>>>> +++ b/include/linux/sunrpc/sched.h
>>>>> @@ -90,8 +90,7 @@ struct rpc_task {
>>>>> #endif
>>>>>      unsigned char        tk_priority : 2,/* Task priority */
>>>>>                  tk_garb_retry : 2,
>>>>> -                tk_cred_retry : 2,
>>>>> -                tk_rebind_retry : 2;
>>>>> +                tk_cred_retry : 2;
>>>>> };
>>>>>
>>>>> typedef void            (*rpc_action)(struct rpc_task *);
>>>>> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
>>>>> index 0b0b9f1eed46..63b438d8564b 100644
>>>>> --- a/net/sunrpc/clnt.c
>>>>> +++ b/net/sunrpc/clnt.c
>>>>> @@ -2050,9 +2050,6 @@ call_bind_status(struct rpc_task *task)
>>>>>              status = -EOPNOTSUPP;
>>>>>              break;
>>>>>          }
>>>>> -        if (task->tk_rebind_retry == 0)
>>>>> -            break;
>>>>> -        task->tk_rebind_retry--;
>>>>>          rpc_delay(task, 3*HZ);
>>>>>          goto retry_timeout;
>>>>>      case -ENOBUFS:
>>>>> diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
>>>>> index be587a308e05..c8321de341ee 100644
>>>>> --- a/net/sunrpc/sched.c
>>>>> +++ b/net/sunrpc/sched.c
>>>>> @@ -817,7 +817,6 @@ rpc_init_task_statistics(struct rpc_task *task)
>>>>>      /* Initialize retry counters */
>>>>>      task->tk_garb_retry = 2;
>>>>>      task->tk_cred_retry = 2;
>>>>> -    task->tk_rebind_retry = 2;
>>>>>
>>>>>      /* starting timestamp */
>>>>>      task->tk_start = ktime_get();
>>>>> -- 
>>>>> 2.9.5
>>>>>
>>>> -- 
>>>> Chuck Lever
> --
> Chuck Lever
>
>