Re: [PATCH] scsi: storvsc: Workaround for virtual DVD SCSI version

[Greg KH <greg@kroah.com>]

On Wed, May 03, 2017 at 03:56:32PM -0700, Stephen Hemminger wrote:
> From: Stephen Hemminger <stephen@networkplumber.org>
> 
> commit f1c635b439a5c01776fe3a25b1e2dc546ea82e6f upstream
> 
> 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
> 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 which works correctly.
> 
> Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
> Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
> ---
>  drivers/scsi/storvsc_drv.c | 27 +++++++++++++++++----------
>  1 file changed, 17 insertions(+), 10 deletions(-)

I've queued this up, but it's interesting how you deleted the changelog
comments here saying this was only needed for 4.11 and no older kernels
:)

thanks,

greg k-h