Re: [PATCH 00/18] ALUA device handler update, part 1

[Hannes Reinecke <hare@suse.de>]

On 11/20/2015 11:47 AM, Christoph Hellwig wrote:
> On Mon, Nov 09, 2015 at 04:08:05PM +0100, Hannes Reinecke wrote:
>> Hi all,
>>
>> here's the first part of my ALUA device handler update.
>> It's mainly bugfixes and minor improvements; the two important
>> things are the addition of VPD parsing functions scsi_vpd_lun_id()
>> and scsi_vpd_tpg_id().
>> This series has been split off from the original 'Asynchronous ALUA'
>> patchset, as these bits are pretty uncontroversial and have a good
>> chance of being merged reasonably soon.
> 
> I've already reviewed most patches, but the other ones looks fine as
> well:
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> 
> Let's get this into the 4.5 queue ASAP an then tackle the actually
> interesting bits next!
> 
I'm all for it.

One thing, though: I don't really agree with Barts objection that
moving to a workqueue would tie in too many resources.
Thing is, I'm not convinces that using a work queue is allocating
too many resources (we're speaking of 460 vs 240 bytes here).
Also we have to retry commands for quite some time (cite the
infamous NetApp takeover/giveback, which can take minutes).
If we were to handle that without workqueue we'd have to initiate
the retry from the end_io callback, causing a quite deep stack
recursion. Which I'm not really fond of.

But if anyone has a better idea on how to handle retries without the
need for workqueues I'm all ears :-)

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		               zSeries & Storage
hare@suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
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HRB 21284 (AG Nürnberg)
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