Re: [PATCH 1/4] block: Add zone flags to queue zone prop.

["Javier González" <javier@javigon.com>]

On 02.07.2020 07:54, Damien Le Moal wrote:
>On 2020/07/02 15:55, Javier González wrote:
>> From: Javier González <javier.gonz@samsung.com>
>>
>> As the zoned block device will have to deal with features that are
>> optional for the backend device, add a flag field to inform the block
>> layer about supported features. This builds on top of
>> blk_zone_report_flags and extendes to the zone report code.
>>
>> 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-zoned.c              | 3 ++-
>>  drivers/block/null_blk_zoned.c | 2 ++
>>  drivers/nvme/host/zns.c        | 1 +
>>  drivers/scsi/sd.c              | 2 ++
>>  include/linux/blkdev.h         | 3 +++
>>  5 files changed, 10 insertions(+), 1 deletion(-)
>>
>> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
>> index 81152a260354..0f156e96e48f 100644
>> --- a/block/blk-zoned.c
>> +++ b/block/blk-zoned.c
>> @@ -312,7 +312,8 @@ int blkdev_report_zones_ioctl(struct block_device *bdev, fmode_t mode,
>>  		return ret;
>>
>>  	rep.nr_zones = ret;
>> -	rep.flags = BLK_ZONE_REP_CAPACITY;
>> +	rep.flags = q->zone_flags;
>
>zone_flags seem to be a fairly generic flags field while rep.flags is only about
>the reported descriptors structure. So you may want to define a
>BLK_ZONE_REP_FLAGS_MASK and have:
>
>	rep.flags = q->zone_flags & BLK_ZONE_REP_FLAGS_MASK;
>
>to avoid flags meaningless for the user being set.
>
>In any case, since *all* zoned block devices now report capacity, I do not
>really see the point to add BLK_ZONE_REP_FLAGS_MASK to q->zone_flags, especially
>considering that you set the flag for all zoned device types, including scsi
>which does not have zone capacity. This makes q->zone_flags rather confusing
>instead of clearly defining the device features as you mentioned in the commit
>message.
>
>I think it may be better to just drop this patch, and if needed, introduce the
>zone_flags field where it may be needed (e.g. OFFLINE zone ioctl support).

I am using this as a way to pass the OFFLINE support flag to the block
layer. I used this too for the attributes. Are you thinking of a
different way to send this?

I believe this fits too for capacity, but we can just pass it in
all report as before if you prefer.

>
>> +
>>  	if (copy_to_user(argp, &rep, sizeof(struct blk_zone_report)))
>>  		return -EFAULT;
>>  	return 0;
>> diff --git a/drivers/block/null_blk_zoned.c b/drivers/block/null_blk_zoned.c
>> index b05832eb21b2..957c2103f240 100644
>> --- a/drivers/block/null_blk_zoned.c
>> +++ b/drivers/block/null_blk_zoned.c
>> @@ -78,6 +78,8 @@ int null_init_zoned_dev(struct nullb_device *dev, struct request_queue *q)
>>  	}
>>
>>  	q->limits.zoned = BLK_ZONED_HM;
>> +	q->zone_flags = BLK_ZONE_REP_CAPACITY;
>> +
>>  	blk_queue_flag_set(QUEUE_FLAG_ZONE_RESETALL, q);
>>  	blk_queue_required_elevator_features(q, ELEVATOR_F_ZBD_SEQ_WRITE);
>>
>> diff --git a/drivers/nvme/host/zns.c b/drivers/nvme/host/zns.c
>> index 0642d3c54e8f..888264261ba3 100644
>> --- a/drivers/nvme/host/zns.c
>> +++ b/drivers/nvme/host/zns.c
>> @@ -81,6 +81,7 @@ int nvme_update_zone_info(struct gendisk *disk, struct nvme_ns *ns,
>>  	}
>>
>>  	q->limits.zoned = BLK_ZONED_HM;
>> +	q->zone_flags = BLK_ZONE_REP_CAPACITY;
>>  	blk_queue_flag_set(QUEUE_FLAG_ZONE_RESETALL, q);
>>  free_data:
>>  	kfree(id);
>> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
>> index d90fefffe31b..b9c920bace28 100644
>> --- a/drivers/scsi/sd.c
>> +++ b/drivers/scsi/sd.c
>> @@ -2967,6 +2967,7 @@ static void sd_read_block_characteristics(struct scsi_disk *sdkp)
>>  	if (sdkp->device->type == TYPE_ZBC) {
>>  		/* Host-managed */
>>  		q->limits.zoned = BLK_ZONED_HM;
>> +		q->zone_flags = BLK_ZONE_REP_CAPACITY;
>>  	} else {
>>  		sdkp->zoned = (buffer[8] >> 4) & 3;
>>  		if (sdkp->zoned == 1 && !disk_has_partitions(sdkp->disk)) {
>> @@ -2983,6 +2984,7 @@ static void sd_read_block_characteristics(struct scsi_disk *sdkp)
>>  					  "Drive-managed SMR disk\n");
>>  		}
>>  	}
>> +
>>  	if (blk_queue_is_zoned(q) && sdkp->first_scan)
>>  		sd_printk(KERN_NOTICE, sdkp, "Host-%s zoned block device\n",
>>  		      q->limits.zoned == BLK_ZONED_HM ? "managed" : "aware");
>> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
>> index 8fd900998b4e..3f2e3425fa53 100644
>> --- a/include/linux/blkdev.h
>> +++ b/include/linux/blkdev.h
>> @@ -512,12 +512,15 @@ struct request_queue {
>>  	 * Stacking drivers (device mappers) may or may not initialize
>>  	 * these fields.
>>  	 *
>> +	 * Flags represent features as described by blk_zone_report_flags in blkzoned.h
>> +	 *
>>  	 * Reads of this information must be protected with blk_queue_enter() /
>>  	 * blk_queue_exit(). Modifying this information is only allowed while
>>  	 * no requests are being processed. See also blk_mq_freeze_queue() and
>>  	 * blk_mq_unfreeze_queue().
>>  	 */
>>  	unsigned int		nr_zones;
>> +	unsigned int		zone_flags;
>>  	unsigned long		*conv_zones_bitmap;
>>  	unsigned long		*seq_zones_wlock;
>>  #endif /* CONFIG_BLK_DEV_ZONED */
>>
>
>And you are missing device-mapper support. DM target devices have a request
>queue that would need to set the zone_flags too.

Ok. I looked at it and I thought that this would be inherited by the
underlying device. I will add it in V3.

Javier


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