[PATCH] storvsc: workaround for virtual DVD SCSI version

[Hannes Reinecke]

On 03/07/2017 06:15 PM, Stephen Hemminger wrote:
> Hyper-V host emulation of SCSI for virtual DVD device reports SCSI
> version 0 (UNKNOWN) but is still capable of supporting REPORTLUN. 
> 
> Without this patch, a GEN2 Linux guest on Hyper-V will not boot 4.11
> successfully with virtual DVD ROM device. What happens is that the
> SCSI scan process falls back to doing sequential probing by INQUIRY.
> But the storvsc driver has a previous workaround that masks/blocks all
> errors reports from INQUIRY (or MODE_SENSE) commands.  This workaround
> causes the scan to then populate a full set of bogus LUN's on the
> target and then sends kernel spinning off into a death spiral doing
> block reads on the non-existent LUNs.
> 
> By setting the correct blacklist flags, the target with the
> DVD device is scanned with REPORTLUN and that works correctly.
> 
> Patch needs to go in current 4.11, it is safe but not necessary
> in older kernels.
> 
> Signed-off-by: Stephen Hemminger <sthemmin at microsoft.com>
> ---
>  drivers/scsi/storvsc_drv.c | 27 +++++++++++++++++----------
>  1 file changed, 17 insertions(+), 10 deletions(-)
> 
> PS: The error handling does need to be fixed (have patches pending)
> but that is interrelated with hotplug and can wait.
> 
Reviewed-by: Hannes Reinecke <hare at suse.com>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
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