On 2010-09-23 23:46, Nicholas A. Bellinger wrote:
> On Sat, 2010-09-18 at 12:58 -0700, Nicholas A. Bellinger wrote:
>> On Fri, 2010-09-17 at 21:45 -0500, Mike Christie wrote:
>>> On 09/17/2010 02:03 PM, Joe Eykholt wrote:
>>>>
>>>> How about instead of adding use_serial_number, let's just have the
>>>> drivers that want a serial number call scsi_cmd_get_serial()
>>>
>>> I think this sounds better.
>>>
>>
>> In that case I will go ahead and add explict scsi_cmd_get_serial() calls
>> to the LLDs that use struct scsi_cmnd->serial_number in anything beyond
>> an obvious and simple informational purpose.
>>
>>> You could also convert drivers to the host tagging if you needed a
>>> unique id for each command sent to a host.
>>
>> Hmmm, what does this entail again..?
>>
>>>
>>>> and stop calling it from scsi_dispatch_cmd()? AFAICT, it's only
>>>> used in debug messages in some drivers. I didn't find other usages
>>>> but didn't do an exhaustive search.
>>>
>>> The comments for serial_number say that it is only supposed to be used
>>> for debugging printks and most drivers use it for that.
>>
>> So I would suppose it would be OK for those drivers to continue to
>> printk serial_number to show the internal serial_number allocation is
>> now disabled by default.
>>
>>> However, it looks like mpt and dpt_i2o are using it for error handling
>>> and/or lookup type of operations. I think the mpt* uses are not needed
>>> in the abort checks.
>>>
>>
>> In that case, then adding an explict scsi_cmd_get_serial() call in mpt*
>> and dpt_i20 ->queuecommand() callers would be a good first step.
>>
>>> And eata is using it for ordering and tracking or something. It could
>>> probably be converted to the host tagging if or what you suggested if it
>>> needs the uniqueue id.
>>
>> Adding an explict scsi_cmd_get_serial() for eata for now, and we can
>> consider LLD canidates for host tag conversion as a future step.
>>
>>>
>>> zfcp looks like it copies it. It does not look like the driver needs it.
>>>
>>
>> Ok, I will look at removing it's usage in zfcp or if necessary add an
>> the explict scsi_cmd_get_serial() call.
>>
>>> scsi_error.c uses it in scsi_try_to_abort_cmd to check if a command has
>>> completed, but I think that can be done by checking if REQ_ATOM_COMPLETE
>>> is set.
>>
>> Hmmm, good catch here. Jejb and hch, does this item work for you..?
>>
>> If so then I will take another peek for any ML uses of a struct
>> scsi_cmnd->serial_number that need to be addressed, and include Joe's
>> and Mike's recommendations into a v3 series.
>>
>
> Greetings Mike and Co,
>
> I was doing some followup on these items for a v3 series and started
> with a patch following mnc's recommendations for dropping the
> scsi_error.c codes depending upon struct scsi_cmnd->serial_number:
>
> diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
> index 1de30eb..f35c127 100644
> --- a/drivers/scsi/scsi_error.c
> +++ b/drivers/scsi/scsi_error.c
> @@ -644,11 +644,7 @@ static int __scsi_try_to_abort_cmd(struct scsi_cmnd *scmd)
> */
> static int scsi_try_to_abort_cmd(struct scsi_cmnd *scmd)
> {
> - /*
> - * scsi_done was called just after the command timed out and before
> - * we had a chance to process it. (db)
> - */
> - if (scmd->serial_number == 0)
> + if (test_bit(REQ_ATOM_COMPLETE, &scmd->request->atomic_flags))
> return SUCCESS;
> return __scsi_try_to_abort_cmd(scmd);
> }
>
> and while building I noticed that the simple single enum
> REQ_ATOM_COMPLETE=0 is
> currently located in block/blk.h and along with blk_mark_rq_complete()
> and blk_clear_rq_complete() for setting this bit within struct
> request->atomic_flags.
>
> jens, hch, tejun, and co, do you guys have a preference how this
> should be handled so that scsi_try_to_abort_cmd() can use proper
> atomic struct request bits here and we can get rid of this (racy..?)
> method of using struct scsi_cmnd->serial_number for anything wrt to
> per struct scsi_cmnd context timeout handling.
Just add a
static inline int blk_test_rq_complete(struct request *rq)
{
return test_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags);
}
in block/blk.h
I need this too for some lockless completion patches I am playing with.
--
Jens Axboe
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