Re: [PATCH] Restart scsi_device_lookup_by_target

[Hannes Reinecke <hare@suse.de>]

Hi Matthew,

Matthew Wilcox wrote:
> On Tue, Jan 13, 2009 at 03:02:27PM +0100, Hannes Reinecke wrote:
>> Matthew Wilcox wrote:
>>> Backwards jumps are generally disapproved of.  How about:
>>>
>>> 	spin_lock_irqsave(shost->host_lock, flags);
>>> 	for (;;) {
>>> 		sdev = __scsi_device_lookup_by_target(starget, sdev, lun);
>>> 		if (!sdev || !scsi_device_get(sdev))
>>> 			break;
>>> 	}
>>> 	spin_unlock_irqrestore(shost->host_lock, flags);
> 
>> I must say I don't really like the for(;;) construct.
> 
> I'd be fine with:
> 
> 	do {
> 		sdev = __scsi_device_lookup_by_target(starget, sdev, lun);
> 	} while (sdev && scsi_device_get(sdev));
> 
> though I find that slightly less clear than the for (;;) construct.
> 
Opinons differ.
Something for the maintainer to decide. James?

>> And it's really confusing as we want to find an sdev, so breaking
>> if it's _not_ found is ... weird.
> 
> Those are the two conditions when we want to stop trying -- if there's
> no device or if the device we've found is bad.  I can definitely see an
> argument for splitting the two conditions to make that more obvious.  I
> can also see an argument for not returning an sdev in the _DEL state
> from __scsi_device_lookup_by_target in the first place.
> 
Not sure if that would work with esp_scsi.c (the other user of
__scsi_device_lookup_by_target()).
And don't have a device to try it with.

But modifying __scsi_device_lookup_by_target() would alter the behaviour,
whereas this patch does not.

Cheers,

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