Re: [PATCH] delay transition requeues for 2 seconds - alua

[Rob Evers <revers@redhat.com>]

On 01/12/2012 04:43 AM, Hannes Reinecke wrote:
> On 01/03/2012 08:20 PM, Rob Evers wrote:
>> From: Rob Evers<revers@redhat.com>
>>
>> When alua targets are transitioning, the scsi midlayer retry mechanism
>> continuously retries the scsi commands that are returning with not ready
>> transitioning status.  The target is not capable of handling the
>> commands for time on the order of several seconds during these transistions.
>>
>> This patch delays the device queue for 2 seconds, which is in the same
>> order of aas transition time.
>>
>> Also, handle all other cases where ADD_TO_MLQUEUE_DELAY could be returned
>> instead of ADD_TO_MLQUEUE as if ADD_TO_MLQUEUE were being returned.
>>
>> Problem found by array partner testing
>>
>> change MLQUEUE_DEV_DLY_RTY to MLQUEUE_DELAYED_RETRY
>>
> I have been working on a different solution, whic
>> Signed-off-by: Rob Evers<revers@redhat.com>
>> ---
>>   drivers/scsi/device_handler/scsi_dh_alua.c |    7 ++++---
>>   drivers/scsi/scsi.c                        |    3 +++
>>   drivers/scsi/scsi_error.c                  |    1 +
>>   drivers/scsi/scsi_lib.c                    |    9 ++++++++-
>>   include/scsi/scsi.h                        |   12 +++++++-----
>>   5 files changed, 23 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
>> index 4ef0212..33b8df7 100644
>> --- a/drivers/scsi/device_handler/scsi_dh_alua.c
>> +++ b/drivers/scsi/device_handler/scsi_dh_alua.c
>> @@ -233,7 +233,7 @@ static void stpg_endio(struct request *req, int error)
>>   			goto done;
>>   		}
>>   		err = alua_check_sense(h->sdev,&sense_hdr);
>> -		if (err == ADD_TO_MLQUEUE) {
>> +		if (err == ADD_TO_MLQUEUE || err == ADD_TO_MLQUEUE_DELAY) {
>>   			err = SCSI_DH_RETRY;
>>   			goto done;
>>   		}
>> @@ -443,7 +443,7 @@ static int alua_check_sense(struct scsi_device *sdev,
>>   			/*
>>   			 * LUN Not Accessible - ALUA state transition
>>   			 */
>> -			return ADD_TO_MLQUEUE;
>> +			return ADD_TO_MLQUEUE_DELAY;
>>   		if (sense_hdr->asc == 0x04&&  sense_hdr->ascq == 0x0b)
>>   			/*
>>   			 * LUN Not Accessible -- Target port in standby state
>> @@ -521,7 +521,8 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
>>   			return SCSI_DH_IO;
>>
>>   		err = alua_check_sense(sdev,&sense_hdr);
>> -		if (err == ADD_TO_MLQUEUE&&  time_before(jiffies, expiry))
>> +		if ((err == ADD_TO_MLQUEUE || err == ADD_TO_MLQUEUE_DELAY)&&
>> +		    time_before(jiffies, expiry))
>>   			goto retry;
>>   		sdev_printk(KERN_INFO, sdev,
>>   			    "%s: rtpg sense code %02x/%02x/%02x\n",
> Actually, this doesn't help if the RTPG command returns with the
> mentioned error; then you'll just continue flooding the array with
> RTPG commands. You'll need to delay the RTPG commands, too.

I thought that the rtpg command would get requeued into the
device queue that is being delayed anyway.

Isn't that true?

Rob