Re: [PATCH] scsi: sd: Implement blacklist option for WRITE SAME w/ UNMAP

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

On Wed, 2017-09-27 at 21:35 -0400, Martin K. Petersen wrote:
> SBC-4 states:
> 
>   "A MAXIMUM UNMAP LBA COUNT field set to a non-zero value indicates the
>    maximum number of LBAs that may be unmapped by an UNMAP command"
> 
>   "A MAXIMUM WRITE SAME LENGTH field set to a non-zero value indicates
>    the maximum number of contiguous logical blocks that the device server
>    allows to be unmapped or written in a single WRITE SAME command."
> 
> Despite the spec being clear on the topic, some devices incorrectly
> expect WRITE SAME commands with the UNMAP bit set to be limited to the
> value reported in MAXIMUM UNMAP LBA COUNT in the Block Limits VPD.
> 
> Implement a blacklist option that can be used to accommodate devices
> with this behavior.
> 
> Reported-by: Bill Kuzeja <William.Kuzeja@stratus.com>
> Reported-by: Ewan D. Milne <emilne@redhat.com>
> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
> ---
>  drivers/scsi/scsi_scan.c    |  3 +++
>  drivers/scsi/sd.c           | 16 ++++++++++++----
>  include/scsi/scsi_device.h  |  1 +
>  include/scsi/scsi_devinfo.h |  1 +
>  4 files changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
> index e7818afeda2b..15590a063ad9 100644
> --- a/drivers/scsi/scsi_scan.c
> +++ b/drivers/scsi/scsi_scan.c
> @@ -956,6 +956,9 @@ static int scsi_add_lun(struct scsi_device *sdev, unsigned char *inq_result,
>  	if (*bflags & BLIST_NO_DIF)
>  		sdev->no_dif = 1;
>  
> +	if (*bflags & BLIST_UNMAP_LIMIT_WS)
> +		sdev->unmap_limit_for_ws = 1;
> +
>  	sdev->eh_timeout = SCSI_DEFAULT_EH_TIMEOUT;
>  
>  	if (*bflags & BLIST_TRY_VPD_PAGES)
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index b18ba3235900..347be7580181 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -715,13 +715,21 @@ static void sd_config_discard(struct scsi_disk *sdkp, unsigned int mode)
>  		break;
>  
>  	case SD_LBP_WS16:
> -		max_blocks = min_not_zero(sdkp->max_ws_blocks,
> -					  (u32)SD_MAX_WS16_BLOCKS);
> +		if (sdkp->device->unmap_limit_for_ws)
> +			max_blocks = sdkp->max_unmap_blocks;
> +		else
> +			max_blocks = sdkp->max_ws_blocks;
> +
> +		max_blocks = min_not_zero(max_blocks, (u32)SD_MAX_WS16_BLOCKS);
>  		break;
>  
>  	case SD_LBP_WS10:
> -		max_blocks = min_not_zero(sdkp->max_ws_blocks,
> -					  (u32)SD_MAX_WS10_BLOCKS);
> +		if (sdkp->device->unmap_limit_for_ws)
> +			max_blocks = sdkp->max_unmap_blocks;
> +		else
> +			max_blocks = sdkp->max_ws_blocks;
> +
> +		max_blocks = min_not_zero(max_blocks, (u32)SD_MAX_WS10_BLOCKS);
>  		break;
>  
>  	case SD_LBP_ZERO:
> diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
> index 82e93ee94708..67c5a9f223f7 100644
> --- a/include/scsi/scsi_device.h
> +++ b/include/scsi/scsi_device.h
> @@ -192,6 +192,7 @@ struct scsi_device {
>  	unsigned no_dif:1;	/* T10 PI (DIF) should be disabled */
>  	unsigned broken_fua:1;		/* Don't set FUA bit */
>  	unsigned lun_in_cdb:1;		/* Store LUN bits in CDB[1] */
> +	unsigned unmap_limit_for_ws:1;	/* Use the UNMAP limit for WRITE SAME */
>  
>  	atomic_t disk_events_disable_depth; /* disable depth for disk events */
>  
> diff --git a/include/scsi/scsi_devinfo.h b/include/scsi/scsi_devinfo.h
> index 9592570e092a..36b03013d629 100644
> --- a/include/scsi/scsi_devinfo.h
> +++ b/include/scsi/scsi_devinfo.h
> @@ -29,5 +29,6 @@
>  #define BLIST_TRY_VPD_PAGES	0x10000000 /* Attempt to read VPD pages */
>  #define BLIST_NO_RSOC		0x20000000 /* don't try to issue RSOC */
>  #define BLIST_MAX_1024		0x40000000 /* maximum 1024 sector cdb length */
> +#define BLIST_UNMAP_LIMIT_WS	0x80000000 /* Use UNMAP limit for WRITE SAME */
>  
>  #endif

Thanks.

Reviewed-by: Ewan D. Milne <emilne@redhat.com>