Re: SCSI regression in 4.11

[James Bottomley <jejb@linux.vnet.ibm.com>]

On Tue, 2017-02-28 at 08:32 -0700, Jens Axboe wrote:
> On 02/28/2017 07:08 AM, Christoph Hellwig wrote:
> > On Mon, Feb 27, 2017 at 05:19:31PM -0800, Stephen Hemminger wrote:
> > > Fixes: ee5242360424 ("scsi: zero per-cmd driver data before each
> > > I/O")
> > > 
> > > but that is already in linux-next.
> > > 
> > > Noticed another place where memset(of the data was being done not
> > > the extra bits.
> > > Tried this, but didn't fix it either...
> > 
> > Are you using blk-mq or the legacy request code?
> 
> Stephen doesn't have MQ set in the config he posted, I'm assuming he 
> didn't boot with scsi_mod.use_blk_mq=true. In a previous email, I 
> asked if turning on MQ makes a difference.

OK, since we're not making much progress, Stephen, could you insert
some debugging into the storvsc driver?  The trace clearly shows we're
getting zeros back in the buffer when we should have data from the
initial scan.  Firstly, does the vmbus think it's transferring any data
for the INQUIRY and READ_CAPACITY commands (looks like
storvsc_command_completion() data_transfer_length)?  If it does,
there's probably an issue initialising the sg list.  If it doesn't,
we're probably sending bogus commands.

James