Re: [PATCH 10/11] hpsa: fix issues with multilun devices

[Tomas Henzl <thenzl@redhat.com>]

On 18.7.2015 18:13, Don Brace wrote:
> From: shane.seymour <shane.seymour@hp.com>
> 
> A regression was introduced into the hpsa driver a while back so
> non-zero LUNs of multi-LUN devices may no longer be presented via
> a SAS based Smart Array. I have not done a bisection to discover
> the change that caused it.
> 
> The CISS firmware specification (available on sourceforge)
> defines an 8 byte lunid that describes devices that the Smart
> Array can see/present to the system. The current code in the hpsa
> driver attempts to find matches for non-zero LUNs with LUN 0 for
> a bus/target by zeroing out byte 4 of the lunid and find a match.
> 
> This method is sufficient for SCSI based Smart Arrays because
> byte 5 is always 0. For SAS based Smart arrays byte 5 of the
> lunid contains the path number for a multipath device and
> either one or two bits (the documentation does not define how
> many bits are used but it appears it may be one only) that
> indicate if the given path number in byte 5 must always be
> used to access that device. Byte 5 may not always be zero.
> 
> The following are lunids (spaces added for clarity) for a
> MSL2024 single drive library connected via a H241 Smart Array:
> 
> 00 00 00 00 01 00 00 01 (changer)
> 00 00 00 00 00 80 00 01 (tape)
> 
> In the 4th byte (counting from 0) you can see that the tape
> is LUN 0 and the changer is LUN 1. The 0x80 set in the 5th byte
> for the tape drive means the driver should force access to
> path 0 (the library in this case was connected to one path only
> anyway).
> 
> After the changes we can see the following in the dmesg output:
> 
> scsi 0:3:0:0: RAID              HP       H241             1.18 \
> PQ: 0 ANSI: 5
> scsi 0:2:0:0: Sequential-Access HP       Ultrium 6-SCSI   354W \
> PQ: 0 ANSI: 6
> scsi 0:2:0:1: Medium Changer    HP       MSL G3 Series    8.70 \
> PQ: 0 ANSI: 5
> 
> Showing that the changer is correctly identified as LUN 1 of
> bus 2 target 0. Before the change the changer device is not seen.
> 
> Suggested-by: shane.seymour <shane.seymour@hp.com>
> Reviewed-by: Kevin Barnett <kevin.barnett@pmcs.com>
> Reviewed-by: Scott Teel <scott.teel@pmcs.com>
> Signed-off-by: Don Brace <don.brace@pmcs.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>

Tomas