linux-kernel - Re: [PATCH v2 5/8] hisi_sas: add v2 hw slot complete internal abort support

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Date:   Wed, 24 Aug 2016 15:07:35 +0100
From:   John Garry <john.garry@...wei.com>
To:     Hannes Reinecke <hare@...e.de>, <jejb@...ux.vnet.ibm.com>,
        <martin.petersen@...cle.com>
CC:     <linuxarm@...wei.com>, <zhangfei.gao@...aro.org>,
        <xuwei5@...ilicon.com>, <john.garry2@...l.dcu.ie>,
        <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 5/8] hisi_sas: add v2 hw slot complete internal abort
 support

On 24/08/2016 13:59, Hannes Reinecke wrote:
> On 08/24/2016 01:05 PM, John Garry wrote:
>> Add code in slot_complete_v2_hw() to deal with the
>> slots which have completed due to internal abort.
>>
>> The status codes have the following meaning:
>> - STAT_IO_ABORTED: the IO has been aborted due to
>> internal abort, whether by device or individual
>> abort command
>> - STAT_IO_COMPLETE: internal abort command has
>> completed successfully for device or individual
>> abort command
>> - STAT_IO_NO_DEVICE: internal abort command has
>> completed for device but cannot find any IO
>> - STAT_IO_NOT_VALID: internal abort command has
>> completed for single command but could not
>> find the command
>>
>> Signed-off-by: John Garry <john.garry@...wei.com>
>> ---
>>  drivers/scsi/hisi_sas/hisi_sas_v2_hw.c | 31 +++++++++++++++++++++++++++++++
>>  1 file changed, 31 insertions(+)
>>
>> diff --git a/drivers/scsi/hisi_sas/hisi_sas_v2_hw.c b/drivers/scsi/hisi_sas/hisi_sas_v2_hw.c
>> index fec1675..bf9b693 100644
>> --- a/drivers/scsi/hisi_sas/hisi_sas_v2_hw.c
>> +++ b/drivers/scsi/hisi_sas/hisi_sas_v2_hw.c
>> @@ -227,6 +227,13 @@
>>  #define CMPLT_HDR_RSPNS_XFRD_MSK	(0x1 << CMPLT_HDR_RSPNS_XFRD_OFF)
>>  #define CMPLT_HDR_ERX_OFF		12
>>  #define CMPLT_HDR_ERX_MSK		(0x1 << CMPLT_HDR_ERX_OFF)
>> +#define CMPLT_HDR_ABORT_STAT_OFF	13
>> +#define CMPLT_HDR_ABORT_STAT_MSK	(0x7 << CMPLT_HDR_ABORT_STAT_OFF)
>> +/* abort_stat */
>> +#define STAT_IO_NOT_VALID		0x1
>> +#define STAT_IO_NO_DEVICE		0x2
>> +#define STAT_IO_COMPLETE		0x3
>> +#define STAT_IO_ABORTED			0x4
>>  /* dw1 */
>>  #define CMPLT_HDR_IPTT_OFF		0
>>  #define CMPLT_HDR_IPTT_MSK		(0xffff << CMPLT_HDR_IPTT_OFF)
>> @@ -1569,6 +1576,30 @@ slot_complete_v2_hw(struct hisi_hba *hisi_hba, struct hisi_sas_slot *slot,
>>  		goto out;
>>  	}
>>
>> +	/* Use SAS+TMF status codes */
>> +	switch ((complete_hdr->dw0 & CMPLT_HDR_ABORT_STAT_MSK)
>> +			>> CMPLT_HDR_ABORT_STAT_OFF) {
>> +	case STAT_IO_ABORTED:
>> +		/* this io has been aborted by abort command */
>> +		ts->stat = SAS_ABORTED_TASK;
>> +		goto out;
>> +	case STAT_IO_COMPLETE:
>> +		/* internal abort command complete */
>> +		ts->stat = TMF_RESP_FUNC_COMPLETE;
>> +		goto out;
>> +	case STAT_IO_NO_DEVICE:
>> +		ts->stat = TMF_RESP_FUNC_COMPLETE;
>> +		goto out;
>> +	case STAT_IO_NOT_VALID:
>> +		/* abort single io, controller don't find
>> +		 * the io need to abort
>> +		 */
>> +		ts->stat = TMF_RESP_FUNC_FAILED;
>> +		goto out;
> Hmm. This will cause the SCSI EH to kick in.
> And then, according to the description abort has succeeded, it's just
> that for some reason the associated command couldn't be found.
> So couldn't this be due to a race condition, and the command has in fact
> been aborted correctly (and the code is just too slow acknowledging it)?
>

Hi Hannes,

I'm not sure I fully get your question.

The internal abort would happen from the SCSI error handling. An example 
would be when the disk was not safely removed and some IO is still in 
flight. In this case the IO will timeout, SCSI EH starts, and we try to 
abort the command in LLDD, by TMF (which would fail) and internal abort.

For internal abort, if the abort command succeeds then 2 things happen:
- abort task completes with status STAT_IO_COMPLETE
- task which was aborted completes with status STAT_IO_ABORTED

If the command does not abort successfully then:
- abort task completes with status STAT_IO_NOT_VALID
- task which we wanted to be aborted does not complete and is probably 
still in the slave device

I hope that this makes it clear.

Thanks,
John

> Cheers,
>
> Hannes
>