[Ocfs2-devel] [PATCH] ocfs2: retry once dlm_dispatch_assert_master failed with ENOMEM

[Joseph Qi]

Thanks for your advice.
I thought about returning DLM_LOCK_RES_OWNER_UNKNOWN, but it would
result in confusion at message sender.
I'll take your idea of retrying 3 times and then resend this patch.

On 2014/4/4 9:26, Wengang wrote:
> O2net is using a single threaded work queue to process network requests.
> Blocking in a handler would block whole network processing.
> As you see, the memory allocation is with GFP_NOFS, if the first try
> failed, the following retries may still fail. Thus it could block a
> while which is not good.
> 
> How about to limit the retries, say, 3 or 5 times. If it still failed to
> get memory, return an error to peer and peer decides to retry or give up.
> 
> thanks,
> wengang
> 
> 于 2014年04月03日 20:45, Joseph Qi 写道:
>> Once dlm_dispatch_assert_master failed in dlm_master_requery_handler,
>> the only reason is ENOMEM. So just retry it instead of BUG().
>>
>> Signed-off-by: Joseph Qi <joseph.qi at huawei.com>
>> ---
>>   fs/ocfs2/dlm/dlmrecovery.c | 11 ++++++++---
>>   1 file changed, 8 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/ocfs2/dlm/dlmrecovery.c b/fs/ocfs2/dlm/dlmrecovery.c
>> index 7035af0..f772d64 100644
>> --- a/fs/ocfs2/dlm/dlmrecovery.c
>> +++ b/fs/ocfs2/dlm/dlmrecovery.c
>> @@ -1685,6 +1685,7 @@ int dlm_master_requery_handler(struct o2net_msg
>> *msg, u32 len, void *data,
>>         hash = dlm_lockid_hash(req->name, req->namelen);
>>   +retry:
>>       spin_lock(&dlm->spinlock);
>>       res = __dlm_lookup_lockres(dlm, req->name, req->namelen, hash);
>>       if (res) {
>> @@ -1693,10 +1694,14 @@ int dlm_master_requery_handler(struct
>> o2net_msg *msg, u32 len, void *data,
>>           if (master == dlm->node_num) {
>>               int ret = dlm_dispatch_assert_master(dlm, res,
>>                                    0, 0, flags);
>> +            /* ENOMEM returns, just retry */
>>               if (ret < 0) {
>> -                mlog_errno(-ENOMEM);
>> -                /* retry!? */
>> -                BUG();
>> +                spin_unlock(&res->spinlock);
>> +                dlm_lockres_put(res);
>> +                spin_unlock(&dlm->spinlock);
>> +                mlog_errno(ret);
>> +                msleep(50);
>> +                goto retry;
>>               }
>>           } else /* put.. incase we are not the master */
>>               dlm_lockres_put(res);
> 
> 
>