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

[Javier González]

On 26.06.2020 01:34, Damien Le Moal wrote:
>On 2020/06/25 21:22, Javier González wrote:
>> From: Javier González <javier.gonz at 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 at samsung.com>
>> Signed-off-by: SelvaKumar S <selvakuma.s1 at samsung.com>
>> Signed-off-by: Kanchan Joshi <joshi.k at samsung.com>
>> Signed-off-by: Nitesh Shetty <nj.shetty at 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 ?

Use case is to transition zones in read-only state to offline when we
are done moving valid data. It is easier to explicitly managing zones
that are not usable by having all under the offline state.

>
>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.

We can do that.

>
>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 ?

AFAIK the transition to offline is only valid when coming from a
read-only state. I did think of adding a check, but I can see that other
transitions go directly to the driver and then the device, so I decided
to follow the same model. If you think it is better, we can add the
check.

Javier