Re: BUG: SCSI INQUIRY thru SCSI_IOCTL_SEND_COMMAND returns no errno for disconnected device

[Jens Axboe <axboe@suse.de>]

On Fri, Oct 08 2004, Lan Tran wrote:
> Thanks Patrick for the tip! After trying out SG_IO, it works, as long
> as we use Mike C's patch.
> 
> Lan
> 
> On Fri, 1 Oct 2004 09:31:31 -0700, Patrick Mansfield <patmans@us.ibm.com> wrote:
> > On Thu, Sep 30, 2004 at 12:43:47PM -0700, Lan Tran wrote:
> > > We have a SAN system set up, where our host is connected to IBM ESS
> > > storage and SVC storage. When we disconnect ALL FC cables between the
> > > host and storage devices, and then send a SCSI INQUIRY using the
> > > SCSI_IOCTL_SEND_COMMAND ioctl to the
> > > sd devices, the ioctl does not return with a failure code. Instead, it
> > > returns with a zero-length buffer.
> > >
> > > Is there a reason why we would get a zeroed-length buffer instead of
> > > an error return code?
> > 
> > SCSI_IOCTL_SEND_COMMAND is deprecated, you should be using SG_IO instead.
> > 
> > There was a bug with SG_IO, it does not correctly set all of the status
> > bytes, a patch has been submitted a few times, Mike C's patch
> > fixed problems compared to ones I posted earlier, this patch:
> > 
> >         http://marc.theaimsgroup.com/?l=linux-scsi&m=108617935710955&w=2
> > 
> > It looks like SCSI_IOCTL_SEND_COMMAND has a similiar issue, in that it
> > only checks the low byte of the results, so for example a DID_NO_CONNECT
> > returned by the qlogic or emulex driver would be ignored.
> > 
> > See drivers/block/scsi_ioctl.c near the end of sg_scsi_ioctl, this:
> > 
> >         err = rq->errors & 0xff;        /* only 8 bit SCSI status */
> > 
> > Compare that to code in drivers/scsi/scsi_ioctl.c near the end of
> > scsi_ioctl_send_command, where the entire result is checked, not just the
> > SCSI byte.

I'll make sure to get that patch finally in. It made it to the bsg tree,
and never further. Thanks for the reminder.

-- 
Jens Axboe