Re: [PATCH RFC 0/9] [SCSI] Enhanced sense and Unit Attention handling

[Ewan Milne <emilne@redhat.com>]

On Wed, 2013-01-23 at 17:19 -0700, Bart Van Assche wrote:
> On Fri, Jan 18, 2013 at 9:27 AM, Ewan D. Milne <emilne@redhat.com> wrote:
> > This patch set adds changes to the SCSI mid-layer, sysfs and scsi_debug
> > to provide enhanced support for Unit Attention conditions, as well as
> > detection of reported sense data overflow conditions and some changes
> > to sense data processing.  It also adds a uevent when the reported
> > capacity changes on an sd device.
> >
> > There was some discussion about this a couple of years ago on the linux-scsi
> > mailing list:  http://marc.info/?l=linux-scsi&m=129702506514742&w=2
> > Although one approach is to send all SCSI sense data to a userspace daemon
> > for processing, this patch set does not take that approach due to the
> > difficulty in reliably delivering all of the data.  An interesting UA
> > condition might not be delivered due to a flood of media errors, for example.
> >
> > The mechanism used is to flag when certain UA ASC/ASCQ codes are received
> > that report asynchronous changes to the storage device configuration.
> > An appropriate uevent is then generated for the scsi_device or scsi_target
> > object.  An aggregation mechanism is used to avoid generating uevents at
> > too high a rate, and to coalesce multiple UAs reported by LUNs on the
> > same target for a REPORTED LUNS DATA HAS CHANGED sense code.
> 
> Does this patch series add a function that allows SCSI LLDs to report
> AEN data to the SCSI core ? What if a SCSI target reports a LUN
> inventory change via AER to e.g. the iSCSI initiator and that
> initiator ignores the AEN data ? Will that result in AEN data being
> ignored and no automatic LUN rescanning ?

Well, what the patch series does is add handling in scsi_check_sense(),
so any sense processing that went through that path would be handled.
I don't think this would apply to AEN, however.  The only AEN handling
that I am aware of was in iscsi-initiator-utils, in userspace, which
did a rescan on the iscsi session when a 3F 0E code was received.

> 
> Bart.