Re: [PATCH] scsi: break from queue depth adjusting loops when device found

[Hannes Reinecke <hare@suse.de>]

On 07/03/2014 07:11 PM, Christoph Hellwig wrote:
> On Thu, Jul 03, 2014 at 10:05:57AM -0500, Stephen M. Cameron wrote:
>> From: Stephen M. Cameron <scameron@beardog.cce.hp.com>
>>
>> Don't loop through all the devices even after
>> finding the one we're looking for
>
> The comments in the code seem to indicate that we want to modify
> the queue depth for all LUNs on a given target.
>
> Ccing Mike and Vasu as they wrote this code.
>
Indeed, that was the idea.
This piece of code tries to keep track of the remote port queue 
depth, which isn't represented at all.
Thing is, each remote target has a target queue depth which can hold 
only so many outstanding SCSI requests. If that is full it'll return 
BUSY for _all_ LUNs served from that port.
And the very _next_ command after the one which filled the target 
queue will get the BUSY status.
So we need to decrease the queue depth on _all_ LUNs here to avoid 
starvation of individual devices.

Hence I guess this is not the correct fix.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
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