Re: [PATCHv3] scsi: disable automatic target scan

[Hannes Reinecke <hare@suse.de>]

On 03/30/2016 09:41 PM, Benjamin Block wrote:
> Hello Hannes,
> 
> I am a bit late here, but as this got pulled and Steffen didn't have
> time to give it a review, I did today.
> 
> On 08:39 Thu 17 Mar     , Hannes Reinecke wrote:
>> On larger installations it is useful to disable automatic LUN
>> scanning, and only add the required LUNs via udev rules.
>> This can speed up bootup dramatically.
>>
>> This patch introduces a new scan module parameter value 'manual',
>> which works like 'none', but can be overriden by setting the 'rescan'
>> value from scsi_scan_target to 'SCSI_SCAN_MANUAL'.
>> And it updates all relevant callers to set the 'rescan' value
>> to 'SCSI_SCAN_MANUAL' if invoked via the 'scan' option in sysfs.
>>
>> Signed-off-by: Hannes Reinecke <hare@suse.de>
>> ---
> 
> [:snip:]
> 
>>
>> diff --git a/drivers/s390/scsi/zfcp_unit.c b/drivers/s390/scsi/zfcp_unit.c
>> index 157d3d2..08bba7c 100644
>> --- a/drivers/s390/scsi/zfcp_unit.c
>> +++ b/drivers/s390/scsi/zfcp_unit.c
>> @@ -26,7 +26,8 @@ void zfcp_unit_scsi_scan(struct zfcp_unit *unit)
>>  	lun = scsilun_to_int((struct scsi_lun *) &unit->fcp_lun);
>>
>>  	if (rport && rport->port_state == FC_PORTSTATE_ONLINE)
>> -		scsi_scan_target(&rport->dev, 0, rport->scsi_target_id, lun, 1);
>> +		scsi_scan_target(&rport->dev, 0, rport->scsi_target_id, lun,
>> +				 SCSI_SCAN_RESCAN);
> 
> I'd rather use the new SCSI_SCAN_MANUAL here. We don't want this to be
> "blocked" by an attribute set in a different (new) code-path and
> config-location.
> 
> This path is used by both, zfcp-recovery and -userinterfaces (sysfs) and
> in both cases we call it with the intend that the scan is really done -
> hence the SCSI_SCAN_MANUAL to force a scan. I'd find it very weird if
> suddenly our users would have to additionally use yet an other config to
> get the old interfaces working properly.
> 
Okay, no problem with that.
zfcp has its own scanning rules (cf allow_lun_scan module parameter), so
setting it to 'MANUAL' will just restore the original behaviour.

Will you be sending a patch for it?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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