Re: [PATCHv3 2/3] scsi: Do not rely on blk-mq for double completions

[Jens Axboe <axboe@kernel.dk>]

On 11/19/18 1:58 AM, Christoph Hellwig wrote:
>> index 5d83a162d03b..c1d5e4e36125 100644
>> --- a/drivers/scsi/scsi_lib.c
>> +++ b/drivers/scsi/scsi_lib.c
>> @@ -1635,8 +1635,11 @@ static blk_status_t scsi_mq_prep_fn(struct request *req)
>>  
>>  static void scsi_mq_done(struct scsi_cmnd *cmd)
>>  {
>> +	if (unlikely(test_and_set_bit(__SCMD_COMPLETE, &cmd->flags)))
>> +		return;
>>  	trace_scsi_dispatch_cmd_done(cmd);
>> -	blk_mq_complete_request(cmd->request);
>> +	if (unlikely(!blk_mq_complete_request(cmd->request)))
>> +		clear_bit(__SCMD_COMPLETE, &cmd->flags);
>>  }
> 
> This looks a little odd to me.  If we didn't complete the command
> someone else did.  Why would we clear the bit in this case?

It's strictly for the fake timeout, it didn't complete it, it just
ignored it. This is an artifact of the weird way that works.


-- 
Jens Axboe