linux-kernel - Re: [EXTERNAL] Re: [PATCH] smb: client: fix first failure in negotiation after server reboot

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Message-ID: <a759b723-05f4-4f47-b9c6-55ea2739da72@huawei.com>
Date: Mon, 16 Jun 2025 10:15:23 +0800
From: "zhangjian (CG)" <zhangjian496@...wei.com>
To: "Shyam Prasad (Azure Files)" <Shyam.Prasad@...rosoft.com>
CC: <linux-cifs@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [EXTERNAL] Re: [PATCH] smb: client: fix first failure in
 negotiation after server reboot

In addition, If negotiation received no response, there are two possible
actions:
1. server_unresponsive may trigger reconnecting again and return true.
2. server_unresponsive may return false and client falls back to
CifsNeedNegotiate state and trigger reconnecting in SMB2_echo.

There two conditions are similar to the stage when first mounting to
cifs server.

On 2025/6/16 10:01, zhangjian (CG) wrote:
> 
> 
> 
> 
> On 2025/6/15 21:08, Shyam Prasad (Azure Files) wrote:
>> Can we have a situation where we just got the sock_recvmsg just timed out, and before we loop back to server_unresponsive, if another parallel negotiate updates lstrp?
> 
> Negotiation only comes when connection is touchable. Client will send a
> negotiation message to server. If we just got the sock_recvmsg timeout
> and loop back to server_unresponsive, it will return false. Client calls
> sock_recvmsg again and wait for negotiation response. Everything is Ok.
> 
>> That will cause us to not detect the server unresponsive situation, even if that did happen.
>> server->lstrp is meant to store the last "response" time from the server.
> 
> server->lstrp is also updated during setting up and aborting connection
> even when there is no response. These can be regarded as initial value
> for server->lstrp.
> I think server->lstrp needs an initial value before negotiation rather
> than connection.
> 
>>
>>
>> Regards,
>>
>> Shyam
>>
>>
>>
>>
>> ________________________________
>> From: Steve French <smfrench@...il.com>
>> Sent: Friday, June 13, 2025 20:53
>> To: zhangjian (CG) <zhangjian496@...wei.com>
>> Cc: Shyam Prasad (Azure Files) <Shyam.Prasad@...rosoft.com>; Paulo Alcantara <pc@...guebit.com>
>> Subject: [EXTERNAL] Re: [PATCH] smb: client: fix first failure in negotiation after server reboot
>>
>> Could you clarify the reproduction scenario? It was a little hard to read
>>
>> On Fri, Jun 13, 2025 at 5:44 AM zhangjian (CG) <zhangjian496@...wei.com> wrote:
>>>
>>> After fabc4ed200f9, server_unresponsive add a condition to check whether
>>> client need to reconnect depending on server->lstrp. When client failed
>>> to reconnect in 180s, client will abort connection and update server->lstrp
>>> for the last time. In the following scene, server->lstrp is too
>>> old, which may cause failure for the first negotiation.
>>>
>>> client                                                 | server
>>> -------------------------------------------------------+------------------
>>> mount to cifs server                                   |
>>> ls                                                     |
>>>                                                        | reboot
>>>     stuck for 180s and return EHOSTDOWN                |
>>>     abort connection and update server->lstrp          |
>>>                                                        | sleep 21s
>>>                                                        | service smb restart
>>> ls                                                     |
>>>     smb_negotiate                                      |
>>>         server_unresponsive cause reconnect [in cifsd] |
>>>         ( tcpStatus == CifsInNegotiate &&              |
>>>                     jiffies > server->lstrp + 20s )        |
>>>         cifs_sync_mid_result return EAGAIN             |
>>>     smb_negotiate return EHOSTDOWN                     |
>>> ls failed                                              |
>>>
>>> The condition (tcpStatus == CifsInNegotiate && jiffies > server->lstrp + 20s)
>>> expect client stay in CifsInNegotiate state for more than 20s. So we update
>>> server->lstrp before last switching into CifsInNegotiate state to avoid
>>> this failure.
>>>
>>> Fixes: fabc4ed200f9 ("smb: client: fix hang in wait_for_response() for
>>> negproto")
>>> Signed-off-by: zhangjian <zhangjian496@...wei.com>
>>> ---
>>>  fs/smb/client/connect.c | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
>>> index 28bc33496..f9aef60f1 100644
>>> --- a/fs/smb/client/connect.c
>>> +++ b/fs/smb/client/connect.c
>>> @@ -4193,6 +4193,7 @@ cifs_negotiate_protocol(const unsigned int xid, struct cifs_ses *ses,
>>>                 return 0;
>>>         }
>>>
>>> +       server->lstrp = jiffies;
>>>         server->tcpStatus = CifsInNegotiate;
>>>         spin_unlock(&server->srv_lock);
>>>
>>> --
>>> 2.33.0
>>
>>
>>
>> --
>> Thanks,
>>
>> Steve
>