RE: [PATCH 4/8] Drivers: scsi: storvsc: Filter WRITE_SAME_16

KY Srinivasan
2014-07-14T02:37:50Z

> -----Original Message-----
> From: KY Srinivasan
> Sent: Sunday, July 13, 2014 11:50 AM
> To: 'Martin K. Petersen'
> Cc: hch@infradead.org; James Bottomley; linux-kernel@vger.kernel.org;
> devel@linuxdriverproject.org; apw@canonical.com; stable@vger.kernel.org;
> linux-scsi@vger.kernel.org; ohering@suse.com; jasowang@redhat.com
> Subject: RE: [PATCH 4/8] Drivers: scsi: storvsc: Filter WRITE_SAME_16
>
>
>
> > -----Original Message-----
> > From: Martin K. Petersen [mailto:martin.petersen@oracle.com]
> > Sent: Sunday, July 13, 2014 5:59 AM
> > To: KY Srinivasan
> > Cc: hch@infradead.org; James Bottomley; linux-kernel@vger.kernel.org;
> > devel@linuxdriverproject.org; apw@canonical.com;
> > stable@vger.kernel.org; linux-scsi@vger.kernel.org; ohering@suse.com;
> > jasowang@redhat.com
> > Subject: Re: [PATCH 4/8] Drivers: scsi: storvsc: Filter WRITE_SAME_16
> >
> > >>>>> "KY" == KY Srinivasan <kys@microsoft.com> writes:
> >
> > KY> Windows hosts do support UNMAP and set the field in the EVPD.
> > KY> However, since the host advertises SPC-2 compliance, Linux does
> > KY> not even query the VPD page.
> >
> > >> If we want to enable UNMAP in this case I'd prefer a blacklist
> > >> entry than trying UNMAP despite the device not advertising it.
> >
> > I agree with that. We could do something like the patch below.
> >
> > However, I do think it's a good idea that you guys are looking into
> > reporting SPC-3.
>
> Thanks Martin; this patch would address our present issues. I will get some
> testing done and report back.

How should we force the flag (BLIST_TRY_VPD_PAGES) to be set.

K. Y
>
> Regards,
>
> K. Y
> >
> >
> > SCSI: Add a blacklist flag which enables VPD page inquiries
> >
> > Despite supporting modern SCSI features some storage devices continue
> > to claim conformance to an older version of the SPC spec. This is done
> > for compatibility with legacy operating systems.
> >
> > Linux by default will not attempt to read VPD pages on devices that
> > claim
> > SPC-2 or older. Introduce a blacklist flag that can be used to trigger
> > VPD page inquiries on devices that are known to support them.
> >
> > Reported-by: KY Srinivasan <kys@microsoft.com>
> > Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
> >
> > diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c index
> > 4a6e4ba5a400..a5b1a224628a 100644
> > --- a/drivers/scsi/scsi_scan.c
> > +++ b/drivers/scsi/scsi_scan.c
> > @@ -949,7 +949,9 @@ static int scsi_add_lun(struct scsi_device *sdev,
> > unsigned char *inq_result,
> >
> > sdev->eh_timeout = SCSI_DEFAULT_EH_TIMEOUT;
> >
> > - if (*bflags & BLIST_SKIP_VPD_PAGES)
> > + if (*bflags & BLIST_TRY_VPD_PAGES)
> > + sdev->try_vpd_pages = 1;
> > + else if (*bflags & BLIST_SKIP_VPD_PAGES)
> > sdev->skip_vpd_pages = 1;
> >
> > transport_configure_device(&sdev->sdev_gendev);
> > diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index
> > 87566b51fcf7..31d32b9077ca 100644
> > --- a/drivers/scsi/sd.c
> > +++ b/drivers/scsi/sd.c
> > @@ -2701,6 +2701,11 @@ static void sd_read_write_same(struct scsi_disk
> > *sdkp, unsigned char *buffer)
> >
> > static int sd_try_extended_inquiry(struct scsi_device *sdp) {
> > + /* Attempt VPD inquiry if the device blacklist explicitly calls
> > + * for it.
> > + */
> > + if (sdp->try_vpd_pages)
> > + return 1;
> > /*
> > * Although VPD inquiries can go to SCSI-2 type devices,
> > * some USB ones crash on receiving them, and the pages diff --git
> > a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h index
> > 9aa38f7b303b..f579408620f0 100644
> > --- a/include/scsi/scsi_device.h
> > +++ b/include/scsi/scsi_device.h
> > @@ -155,6 +155,7 @@ struct scsi_device {
> > unsigned skip_ms_page_8:1; /* do not use MODE SENSE page 0x08
> > */
> > unsigned skip_ms_page_3f:1; /* do not use MODE SENSE page 0x3f
> > */
> > unsigned skip_vpd_pages:1; /* do not read VPD pages */
> > + unsigned try_vpd_pages:1; /* attempt to read VPD pages */
> > unsigned use_192_bytes_for_3f:1; /* ask for 192 bytes from page
> 0x3f
> > */
> > unsigned no_start_on_add:1; /* do not issue start on add */
> > unsigned allow_restart:1; /* issue START_UNIT in error handler */
> > diff --git a/include/scsi/scsi_devinfo.h b/include/scsi/scsi_devinfo.h
> > index 8670c04e199e..1fdd6fc5492b 100644
> > --- a/include/scsi/scsi_devinfo.h
> > +++ b/include/scsi/scsi_devinfo.h
> > @@ -34,4 +34,5 @@
> > #define BLIST_SKIP_VPD_PAGES 0x4000000 /* Ignore SBC-3 VPD pages
> > */
> > #define BLIST_SCSI3LUN 0x8000000 /* Scan more than 256
> > LUNs
> > for sequential scan */
> > +#define BLIST_TRY_VPD_PAGES 0x10000000 /* Attempt to read VPD
> > pages */
> > #endif