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

[KY Srinivasan]

> -----Original Message-----
> From: Martin K. Petersen [mailto:martin.petersen@xxxxxxxxxx]
> Sent: Sunday, July 13, 2014 5:59 AM
> To: KY Srinivasan
> Cc: hch@xxxxxxxxxxxxx; James Bottomley; linux-kernel@xxxxxxxxxxxxxxx;
> devel@xxxxxxxxxxxxxxxxxxxxxx; apw@xxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx;
> linux-scsi@xxxxxxxxxxxxxxx; ohering@xxxxxxxx; jasowang@xxxxxxxxxx
> Subject: Re: [PATCH 4/8] Drivers: scsi: storvsc: Filter WRITE_SAME_16
> 
> >>>>> "KY" == KY Srinivasan <kys@xxxxxxxxxxxxx> 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 not
> KY> 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.

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@xxxxxxxxxxxxx>
> Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
> 
> 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
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