Re: [PATCH 1/3] scsi_dh_rdac: switch to scsi_execute_req_flags()

["Ewan D. Milne" <emilne@redhat.com>]

On Wed, 2016-11-02 at 22:27 +0100, Hannes Reinecke wrote:
> On 11/02/2016 04:44 PM, Ewan D. Milne wrote:
> > In this and other places the patch changes the code from submitting the
> > INQUIRY/EVPD command for the page it wants, to calling scsi_get_vpd_page().
> > scsi_get_vpd_page() will return -EINVAL if the device did not report in
> > VPD page 0 that the requested page is in the list of supported pages.
> > Did you actually verify that the RDAC returns all of these VPD pages in
> > its VPD page 0 list?
> >
> > I mean, I know it's supposed to, but these are old devices.
> >
> Errm.
> 
> Old? Don't tell that to the E-Series folk; you'll never again get 
> something sponsored :-)
> 
> No, seriously: RDAC mode is continued to be supported even on the latest 
> models, and all firmware revisions I've got support VPD page 0x0.
> And incidentally, this is the very same method we're using for basically 
> all tools accessing VPD page 0x83, be it in the kernel or something like 
> sg3_utils.
> _Not_ asking for page 0x0 lead to crashes on several older devices.

You're right, I was curious, so I resurrected our old RDAC, and it does
in fact report the necessary supported VPD pages:

# sg_vpd -H /dev/sg4
Supported VPD pages VPD page:
 00     20 00 00 12 00 80 83 85  86 87 b0 b1 c0 c1 c2 c3     ...............
 10     c4 c8 c9 ca d0 e0                                   ......

My concern was that older devices might not do this, I think there have
been some arrays that had hidden commands/pages.

-Ewan