Re: [PATCH v3 0/6] [SCSI] Enhanced sense and Unit Attention handling

[Ewan Milne <emilne@redhat.com>]

On Mon, 2013-07-22 at 15:31 +0000, James Bottomley wrote:
> Ping on this, please.
> 
> I have another possible consumer of this infrastructure, when it's
> ready, which is the SCSI RAID drivers.  We've been getting complaints
> that there's no event we get from them when a RAID system goes from
> online -> degraded which should be the sysadmin's cue to go in and
> replace the disk (well, this isn't quite true, a lot come with
> proprietary monitoring daemons which do this, but they're pretty unique
> per controller).
> 
> I was thinking we might resurrect the orphaned raid_class.c to do this
> and give a universally displayable but rudimentary view of the topology
> and health of the device and add an easy hook for RAID events.
> 
> James
> 

I'm testing a v4 version of these patches, which address your earlier
comments.  I'm still working on the code to suppress the duplicate
REPORTED LUNS DATA HAS CHANGED unit attentions from multiple LUNs.
As I mentioned in my earlier mail, doing this with the expected_cc_ua
mechanism is imperfect, because SCSI-3 devices will stop reporting it
when one of the LUNs on the target *receives* a REPORT LUNs command, and
it is difficult to know when this happens.  I'm trying out clearing
the flag before the SCSI scan code issues a REPORT LUNs, that might be
good enough.  (It doesn't handle someone from sending this command
through the sg driver, though.)

Will post the v4 soon.

-Ewan