Re: [PATCH 3/6] block: add support for zone offline transition

[Damien Le Moal <Damien.LeMoal@wdc.com>]

On 2020/06/25 21:22, Javier González wrote:
> From: Javier González <javier.gonz@samsung.com>
> 
> Add support for offline transition on the zoned block device using the
> new zone management IOCTL
> 
> Signed-off-by: Javier González <javier.gonz@samsung.com>
> Signed-off-by: SelvaKumar S <selvakuma.s1@samsung.com>
> Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
> Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
> ---
>  block/blk-core.c              | 2 ++
>  block/blk-zoned.c             | 3 +++
>  drivers/nvme/host/core.c      | 3 +++
>  include/linux/blk_types.h     | 3 +++
>  include/linux/blkdev.h        | 1 -
>  include/uapi/linux/blkzoned.h | 1 +
>  6 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 03252af8c82c..589cbdacc5ec 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -140,6 +140,7 @@ static const char *const blk_op_name[] = {
>  	REQ_OP_NAME(ZONE_CLOSE),
>  	REQ_OP_NAME(ZONE_FINISH),
>  	REQ_OP_NAME(ZONE_APPEND),
> +	REQ_OP_NAME(ZONE_OFFLINE),
>  	REQ_OP_NAME(WRITE_SAME),
>  	REQ_OP_NAME(WRITE_ZEROES),
>  	REQ_OP_NAME(SCSI_IN),
> @@ -1030,6 +1031,7 @@ generic_make_request_checks(struct bio *bio)
>  	case REQ_OP_ZONE_OPEN:
>  	case REQ_OP_ZONE_CLOSE:
>  	case REQ_OP_ZONE_FINISH:
> +	case REQ_OP_ZONE_OFFLINE:
>  		if (!blk_queue_is_zoned(q))
>  			goto not_supported;
>  		break;
> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> index 29194388a1bb..704fc15813d1 100644
> --- a/block/blk-zoned.c
> +++ b/block/blk-zoned.c
> @@ -416,6 +416,9 @@ int blkdev_zone_mgmt_ioctl(struct block_device *bdev, fmode_t mode,
>  	case BLK_ZONE_MGMT_RESET:
>  		op = REQ_OP_ZONE_RESET;
>  		break;
> +	case BLK_ZONE_MGMT_OFFLINE:
> +		op = REQ_OP_ZONE_OFFLINE;
> +		break;
>  	default:
>  		return -ENOTTY;
>  	}
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index f1215523792b..5b95c81d2a2d 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -776,6 +776,9 @@ blk_status_t nvme_setup_cmd(struct nvme_ns *ns, struct request *req,
>  	case REQ_OP_ZONE_FINISH:
>  		ret = nvme_setup_zone_mgmt_send(ns, req, cmd, NVME_ZONE_FINISH);
>  		break;
> +	case REQ_OP_ZONE_OFFLINE:
> +		ret = nvme_setup_zone_mgmt_send(ns, req, cmd, NVME_ZONE_OFFLINE);
> +		break;
>  	case REQ_OP_WRITE_ZEROES:
>  		ret = nvme_setup_write_zeroes(ns, req, cmd);
>  		break;
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index 16b57fb2b99c..b3921263c3dd 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -316,6 +316,8 @@ enum req_opf {
>  	REQ_OP_ZONE_FINISH	= 12,
>  	/* write data at the current zone write pointer */
>  	REQ_OP_ZONE_APPEND	= 13,
> +	/* Transition a zone to offline */
> +	REQ_OP_ZONE_OFFLINE	= 14,
>  
>  	/* SCSI passthrough using struct scsi_request */
>  	REQ_OP_SCSI_IN		= 32,
> @@ -456,6 +458,7 @@ static inline bool op_is_zone_mgmt(enum req_opf op)
>  	case REQ_OP_ZONE_OPEN:
>  	case REQ_OP_ZONE_CLOSE:
>  	case REQ_OP_ZONE_FINISH:
> +	case REQ_OP_ZONE_OFFLINE:
>  		return true;
>  	default:
>  		return false;
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index bd8521f94dc4..8308d8a3720b 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -372,7 +372,6 @@ extern int blkdev_zone_ops_ioctl(struct block_device *bdev, fmode_t mode,
>  				  unsigned int cmd, unsigned long arg);
>  extern int blkdev_zone_mgmt_ioctl(struct block_device *bdev, fmode_t mode,
>  				  unsigned int cmd, unsigned long arg);
> -
>  #else /* CONFIG_BLK_DEV_ZONED */
>  
>  static inline unsigned int blkdev_nr_zones(struct gendisk *disk)
> diff --git a/include/uapi/linux/blkzoned.h b/include/uapi/linux/blkzoned.h
> index a8c89fe58f97..d0978ee10fc7 100644
> --- a/include/uapi/linux/blkzoned.h
> +++ b/include/uapi/linux/blkzoned.h
> @@ -155,6 +155,7 @@ enum blk_zone_action {
>  	BLK_ZONE_MGMT_FINISH	= 0x2,
>  	BLK_ZONE_MGMT_OPEN	= 0x3,
>  	BLK_ZONE_MGMT_RESET	= 0x4,
> +	BLK_ZONE_MGMT_OFFLINE	= 0x5,
>  };
>  
>  /**
> 

As mentioned in previous email, the usefulness of this is dubious. Please
elaborate in the commit message. Sure NVMe ZNS defines this and we can support
it. But without a good use case, what is the point ?

scsi SD driver will return BLK_STS_NOTSUPP if this offlining is sent to a
ZBC/ZAC drive. Not nice. Having a sysfs attribute "max_offline_zone_sectors" or
the like to indicate support by the device or not would be nicer.

Does offling ALL zones make any sense ? Because this patch does not prevent the
use of the REQ_ZONE_ALL flags introduced in patch 2. Probably not a good idea to
allow offlining all zones, no ?

-- 
Damien Le Moal
Western Digital Research