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Subject: Re: [PATCH 2/2] NFS: Limit the number of retries
To:     Trond Myklebust <trondmy@hammerspace.com>,
        "anna.schumaker@netapp.com" <anna.schumaker@netapp.com>
Cc:     "chenwenle@huawei.com" <chenwenle@huawei.com>,
        "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "nixiaoming@huawei.com" <nixiaoming@huawei.com>
References: <20201102162438.14034-1-chenwenle@huawei.com>
 <20201102162438.14034-3-chenwenle@huawei.com>
 <8db50c039cb8b8325bb428c60ff005b899654fb4.camel@hammerspace.com>
From:   Wenle Chen <solomonchenclever@gmail.com>
Message-ID: <ebee08ee-ecbe-c47c-1f7c-799f86b3879c@gmail.com>
Date:   Wed, 4 Nov 2020 19:33:48 +0800
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Trond Myklebust 於 2020/11/3 上午1:45 寫道:
> On Tue, 2020-11-03 at 00:24 +0800, Wenle Chen wrote:
>>    We can't wait forever, even if the state
>> is always delayed.
>>
>> Signed-off-by: Wenle Chen <chenwenle@huawei.com>
>> ---
>>   fs/nfs/nfs4proc.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
>> index f6b5dc792b33..bb2316bf13f6 100644
>> --- a/fs/nfs/nfs4proc.c
>> +++ b/fs/nfs/nfs4proc.c
>> @@ -7390,15 +7390,17 @@ int nfs4_lock_delegation_recall(struct
>> file_lock *fl, struct nfs4_state *state,
>>   {
>>          struct nfs_server *server = NFS_SERVER(state->inode);
>>          int err;
>> +       int retry = 3;
>>   
>>          err = nfs4_set_lock_state(state, fl);
>>          if (err != 0)
>>                  return err;
>>          do {
>>                  err = _nfs4_do_setlk(state, F_SETLK, fl,
>> NFS_LOCK_NEW);
>> -               if (err != -NFS4ERR_DELAY)
>> +               if (err != -NFS4ERR_DELAY || retry == 0)
>>                          break;
>>                  ssleep(1);
>> +               --retry;
>>          } while (1);
>>          return nfs4_handle_delegation_recall_error(server, state,
>> stateid, fl, err);
>>   }
> 
> This patch will just cause the locks to be silently lost, no?
> 
This loop was introduced in commit 3d7a9520f0c3e to simplify the delay 
retry loop. Before this, the function nfs4_lock_delegation_recall would 
return a -EAGAIN to do a whole retry loop.

When we retried three times and waited three seconds, it was still in 
delay. I think we can get a whole loop and check the other points if it 
was changed or not. It is just a proposal.