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

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

On 2020/06/26 15:09, Javier González wrote:
> On 26.06.2020 01:34, Damien Le Moal wrote:
>> 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 ?
> 
> 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.

Then adding a simple BLKZONEOFFLINE ioctl, similar to open, close, finish and
reset, would be enough. No need for all the new zone management ioctl with flags
plumbing.

> 
>>
>> 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.

My point was that the REQ_ZONE_ALL flag would make no sense for offlining zones
but this patch does not have anything checking that. There is no point in
sending a command that is known to be incorrect to the drive...

> 
> Javier
> 


-- 
Damien Le Moal
Western Digital Research