Re: [PATCH v2] scsi: target: core: check SR field in REPORT LUNS

Roman Bolshakov
2021-01-26T17:20:47Z

On Fri, Jan 22, 2021 at 11:42:51PM +0100, David Disseldorp wrote:
> On Wed, 20 Jan 2021 13:27:00 +0300, Dmitry Bogdanov wrote:
>
> > Now REPORT LUNS for software device servers always reports all luns
> > regardless of SELECT REPORT field.
> > Add handling of that field according to SPC-4:
> > * accept known values,
> > * reject unknown values.
>
> We currently advertise SPC-3 VERSION compliance via standard INQUIRY
> data, so I think we should either support SPC-3 SELECT REPORT values or
> bump the VERSION field (SPC-4 behaviour is already scattered throughout
> LIO).
> Out of curiosity, do you know of any initiators which use this field?
>

Hi David,

SELECT REPORT field can be used for vVOL (LU conglomerate) discovery and
for well-known lun listing.

The field is used by VMware ESXi:
https://support.purestorage.com/Solutions/VMware_Platform_Guide/User_Guides_for_VMware_Solutions/Virtual_Volumes_User_Guide/vVols_User_Guide%3A_Protocol_Endpoints

"PEs greatly extend the number of vVols that can be connected to an ESXi
cluster; each PE can have up to 16,383 vVols per host bound to it
simultaneously. Moreover, a new binding does not require a complete I/O
rescan. Instead, ESXi issues a REPORT_LUNS SCSI command with SELECT
REPORT to the PE to which the sub-lun is bound. The PE returns a list of
sub-lun IDs for the vVols bound to that host. In large clusters,
REPORT_LUNS is significantly faster than a full I/O rescan because it is
more precisely targeted."

The post also confirms that:
https://sourceforge.net/p/scst/mailman/message/33030432/

A few more targets that support SELECT REPORT field below.

Sun/Oracle tape library:
https://docs.oracle.com/en/storage/tape-storage/storagetek-sl150-modular-tape-library/slorm/report-luns-a0h.html#GUID-4140F40D-BD9A-495C-9A86-8BD7E91C985C

IBM Flash Storage:
https://www.ibm.com/support/pages/sites/default/files/support/ssg/ssgdocs.nsf/0/95d7115d7eb428e485257f80005cc3a7/%24FILE/FlashSystem_840_SCSI_Interface_Manual_1.2.pdf

With regards to bumping TCM to SPC-4, are there any objections if we
submit a separate patch for that? Or resubmit a series with the patch?

Thanks,
Roman