Re: [PATCH v2] block: ublk: enable zoned storage support

[Ming Lei <ming.lei@redhat.com>]

On Fri, Feb 24, 2023 at 09:05:01PM +0100, Andreas Hindborg wrote:
> Add zoned storage support to ublk: report_zones and operations:
>  - REQ_OP_ZONE_OPEN
>  - REQ_OP_ZONE_CLOSE
>  - REQ_OP_ZONE_FINISH
>  - REQ_OP_ZONE_RESET
> 
> This allows implementation of zoned storage devices in user space. An
> example user space implementation based on ubdsrv is available [1].
> 
> [1] https://github.com/metaspace/ubdsrv/commit/14a2b708f74f70cfecb076d92e680dc718cc1f6d

As I suggested, please write one simple & clean zoned target for verifying
the interface, and better to not add to tgt_null.c.

> 
> Signed-off-by: Andreas Hindborg <a.hindborg@samsung.com>
> ---
> Changes since v1:
>  - Fixed conditional compilation bug
>  - Refactored to collect conditional code additions together
>  - Fixed style errors
>  - Zero stack allocated value used for zone report
> 
> Reported-by: Niklas Cassel <Niklas.Cassel@wdc.com>
> Reported-by: kernel test robot <lkp@intel.com>
> Link: https://lore.kernel.org/oe-kbuild-all/202302250222.XOrw9j6z-lkp@intel.com/
> v1: https://lore.kernel.org/linux-block/20230224125950.214779-1-nmi@metaspace.dk/
> 
>  drivers/block/ublk_drv.c      | 150 ++++++++++++++++++++++++++++++++--
>  include/uapi/linux/ublk_cmd.h |  18 ++++
>  2 files changed, 162 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index 6368b56eacf1..37e516903867 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -20,6 +20,7 @@
>  #include <linux/major.h>
>  #include <linux/wait.h>
>  #include <linux/blkdev.h>
> +#include <linux/blkzoned.h>
>  #include <linux/init.h>
>  #include <linux/swap.h>
>  #include <linux/slab.h>
> @@ -51,10 +52,12 @@
>  		| UBLK_F_URING_CMD_COMP_IN_TASK \
>  		| UBLK_F_NEED_GET_DATA \
>  		| UBLK_F_USER_RECOVERY \
> -		| UBLK_F_USER_RECOVERY_REISSUE)
> +		| UBLK_F_USER_RECOVERY_REISSUE \
> +		| UBLK_F_ZONED)
>  
>  /* All UBLK_PARAM_TYPE_* should be included here */
> -#define UBLK_PARAM_TYPE_ALL (UBLK_PARAM_TYPE_BASIC | UBLK_PARAM_TYPE_DISCARD)
> +#define UBLK_PARAM_TYPE_ALL (UBLK_PARAM_TYPE_BASIC | UBLK_PARAM_TYPE_DISCARD \
> +			     | UBLK_PARAM_TYPE_ZONED)
>  
>  struct ublk_rq_data {
>  	struct llist_node node;
> @@ -187,6 +190,98 @@ static DEFINE_MUTEX(ublk_ctl_mutex);
>  
>  static struct miscdevice ublk_misc;
>  
> +#ifdef CONFIG_BLK_DEV_ZONED
> +static void ublk_set_nr_zones(struct ublk_device *ub)
> +{
> +	const struct ublk_param_basic *p = &ub->params.basic;
> +
> +	if (ub->dev_info.flags & UBLK_F_ZONED && p->chunk_sectors)
> +		ub->ub_disk->nr_zones = p->dev_sectors / p->chunk_sectors;
> +}
> +
> +static void ublk_dev_param_zoned_apply(struct ublk_device *ub)
> +{
> +	const struct ublk_param_zoned *p = &ub->params.zoned;
> +
> +	if (ub->dev_info.flags & UBLK_F_ZONED) {
> +		disk_set_max_active_zones(ub->ub_disk, p->max_active_zones);
> +		disk_set_max_open_zones(ub->ub_disk, p->max_open_zones);
> +	}
> +}
> +
> +static int ublk_revalidate_disk_zones(struct gendisk *disk)
> +{
> +	return blk_revalidate_disk_zones(disk, NULL);
> +}
> +
> +static int ublk_report_zones(struct gendisk *disk, sector_t sector,
> +			     unsigned int nr_zones, report_zones_cb cb,
> +			     void *data)
> +{
> +	struct ublk_device *ub;
> +	unsigned int zone_size;
> +	unsigned int first_zone;
> +	int ret = 0;
> +
> +	ub = disk->private_data;
> +
> +	if (!(ub->dev_info.flags & UBLK_F_ZONED))
> +		return -EINVAL;
> +
> +	zone_size = disk->queue->limits.chunk_sectors;
> +	first_zone = sector >> ilog2(zone_size);
> +	nr_zones = min(ub->ub_disk->nr_zones - first_zone, nr_zones);
> +
> +	for (unsigned int i = 0; i < nr_zones; i++) {

The local variable 'i' needs to be declared in the front part
of this function body.

> +		struct request *req;
> +		blk_status_t status;
> +		struct blk_zone info = {0};
> +
> +		req = blk_mq_alloc_request(disk->queue, REQ_OP_DRV_IN, 0);
> +
> +		if (IS_ERR(req)) {
> +			ret = PTR_ERR(req);
> +			goto out;
> +		}
> +
> +		req->__sector = sector;

Why is req->__sector set?

> +
> +		ret = blk_rq_map_kern(disk->queue, req, &info, sizeof(info),
> +				      GFP_KERNEL);
> +
> +		if (ret)
> +			goto out;
> +
> +		status = blk_execute_rq(req, 0);
> +		ret = blk_status_to_errno(status);
> +		if (ret)
> +			goto out;
> +
> +		blk_mq_free_request(req);
> +
> +		ret = cb(&info, i, data);
> +		if (ret)
> +			goto out;
> +
> +		/* A zero length zone means don't ask for more zones */
> +		if (!info.len) {
> +			nr_zones = i;
> +			break;
> +		}
> +
> +		sector += zone_size;
> +	}

I'd suggest to report as many as possible zones in one command, and
the dev_info.max_io_buf_bytes is the max allowed buffer size for one
command, please refer to nvme_ns_report_zones().

Also we are going to extend ublk in the multiple LUN/NS style, and I
guess that won't be one issue since ->report_zones() is always done on
disk level, right?

> +	ret = nr_zones;
> +
> + out:
> +	return ret;
> +}
> +#else
> +void ublk_set_nr_zones(struct ublk_device *ub);
> +void ublk_dev_param_zoned_apply(struct ublk_device *ub);
> +int ublk_revalidate_disk_zones(struct gendisk *disk);
> +#endif
> +
>  static void ublk_dev_param_basic_apply(struct ublk_device *ub)
>  {
>  	struct request_queue *q = ub->ub_disk->queue;
> @@ -212,6 +307,9 @@ static void ublk_dev_param_basic_apply(struct ublk_device *ub)
>  		set_disk_ro(ub->ub_disk, true);
>  
>  	set_capacity(ub->ub_disk, p->dev_sectors);
> +
> +	if (IS_ENABLED(CONFIG_BLK_DEV_ZONED))
> +		ublk_set_nr_zones(ub);
>  }
>  
>  static void ublk_dev_param_discard_apply(struct ublk_device *ub)
> @@ -268,6 +366,9 @@ static int ublk_apply_params(struct ublk_device *ub)
>  	if (ub->params.types & UBLK_PARAM_TYPE_DISCARD)
>  		ublk_dev_param_discard_apply(ub);
>  
> +	if (IS_ENABLED(CONFIG_BLK_DEV_ZONED) && (ub->params.types & UBLK_PARAM_TYPE_ZONED))
> +		ublk_dev_param_zoned_apply(ub);
> +
>  	return 0;
>  }
>  
> @@ -361,9 +462,13 @@ static void ublk_free_disk(struct gendisk *disk)
>  	put_device(&ub->cdev_dev);
>  }
>  
> +
>  static const struct block_device_operations ub_fops = {
> -	.owner =	THIS_MODULE,
> -	.free_disk =	ublk_free_disk,
> +	.owner = THIS_MODULE,
> +	.free_disk = ublk_free_disk,
> +#ifdef CONFIG_BLK_DEV_ZONED
> +	.report_zones = ublk_report_zones,
> +#endif

Define one null ublk_report_zones in #else branch of the above #ifdef, then we
can save one #ifdef.

>  };
>  
>  #define UBLK_MAX_PIN_PAGES	32
> @@ -499,7 +604,7 @@ static int ublk_unmap_io(const struct ublk_queue *ubq,
>  {
>  	const unsigned int rq_bytes = blk_rq_bytes(req);
>  
> -	if (req_op(req) == REQ_OP_READ && ublk_rq_has_data(req)) {
> +	if ((req_op(req) == REQ_OP_READ || req_op(req) == REQ_OP_DRV_IN) && ublk_rq_has_data(req)) {
>  		struct ublk_map_data data = {
>  			.ubq	=	ubq,
>  			.rq	=	req,
> @@ -566,6 +671,26 @@ static blk_status_t ublk_setup_iod(struct ublk_queue *ubq, struct request *req)
>  	case REQ_OP_WRITE_ZEROES:
>  		ublk_op = UBLK_IO_OP_WRITE_ZEROES;
>  		break;
> +#ifdef CONFIG_BLK_DEV_ZONED
> +	case REQ_OP_ZONE_OPEN:
> +		ublk_op = UBLK_IO_OP_ZONE_OPEN;
> +		break;
> +	case REQ_OP_ZONE_CLOSE:
> +		ublk_op = UBLK_IO_OP_ZONE_CLOSE;
> +		break;
> +	case REQ_OP_ZONE_FINISH:
> +		ublk_op = UBLK_IO_OP_ZONE_FINISH;
> +		break;
> +	case REQ_OP_ZONE_RESET:
> +		ublk_op = UBLK_IO_OP_ZONE_RESET;
> +		break;
> +	case REQ_OP_DRV_IN:
> +		ublk_op = UBLK_IO_OP_DRV_IN;
> +		break;
> +	case REQ_OP_ZONE_APPEND:
> +		/* We do not support zone append yet */
> +		fallthrough;
> +#endif

The above '#ifdef' is needn't, since  OP_ZONE should be defined no
matter if CONFIG_BLK_DEV_ZONED is enabled or not.

>  	default:
>  		return BLK_STS_IOERR;
>  	}
> @@ -612,7 +737,8 @@ static void ublk_complete_rq(struct request *req)
>  	 *
>  	 * Both the two needn't unmap.
>  	 */
> -	if (req_op(req) != REQ_OP_READ && req_op(req) != REQ_OP_WRITE) {
> +	if (req_op(req) != REQ_OP_READ && req_op(req) != REQ_OP_WRITE &&
> +	    req_op(req) != REQ_OP_DRV_IN) {
>  		blk_mq_end_request(req, BLK_STS_OK);
>  		return;
>  	}
> @@ -1535,6 +1661,15 @@ static int ublk_ctrl_start_dev(struct io_uring_cmd *cmd)
>  	if (ret)
>  		goto out_put_disk;
>  
> +	if (IS_ENABLED(CONFIG_BLK_DEV_ZONED) &&
> +	    ub->dev_info.flags & UBLK_F_ZONED) {
> +		disk_set_zoned(disk, BLK_ZONED_HM);
> +		blk_queue_required_elevator_features(disk->queue, ELEVATOR_F_ZBD_SEQ_WRITE);
> +		ret = ublk_revalidate_disk_zones(disk);
> +		if (ret)
> +			goto out_put_disk;
> +	}
> +
>  	get_device(&ub->cdev_dev);
>  	ret = add_disk(disk);
>  	if (ret) {
> @@ -1673,6 +1808,9 @@ static int ublk_ctrl_add_dev(struct io_uring_cmd *cmd)
>  	if (!IS_BUILTIN(CONFIG_BLK_DEV_UBLK))
>  		ub->dev_info.flags |= UBLK_F_URING_CMD_COMP_IN_TASK;
>  
> +	if (!IS_ENABLED(CONFIG_BLK_DEV_ZONED))
> +		ub->dev_info.flags &= ~UBLK_F_ZONED;
> +
>  	/* We are not ready to support zero copy */
>  	ub->dev_info.flags &= ~UBLK_F_SUPPORT_ZERO_COPY;
>  
> diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
> index 8f88e3a29998..074b97821575 100644
> --- a/include/uapi/linux/ublk_cmd.h
> +++ b/include/uapi/linux/ublk_cmd.h
> @@ -78,6 +78,10 @@
>  #define UBLK_F_USER_RECOVERY	(1UL << 3)
>  
>  #define UBLK_F_USER_RECOVERY_REISSUE	(1UL << 4)
> +/*
> + * Enable zoned device support
> + */
> +#define UBLK_F_ZONED (1ULL << 5)
>  
>  /* device state */
>  #define UBLK_S_DEV_DEAD	0
> @@ -129,6 +133,12 @@ struct ublksrv_ctrl_dev_info {
>  #define		UBLK_IO_OP_DISCARD	3
>  #define		UBLK_IO_OP_WRITE_SAME	4
>  #define		UBLK_IO_OP_WRITE_ZEROES	5
> +#define		UBLK_IO_OP_ZONE_OPEN		10
> +#define		UBLK_IO_OP_ZONE_CLOSE		11
> +#define		UBLK_IO_OP_ZONE_FINISH		12
> +#define		UBLK_IO_OP_ZONE_APPEND		13
> +#define		UBLK_IO_OP_ZONE_RESET		15
> +#define		UBLK_IO_OP_DRV_IN		34
>  
>  #define		UBLK_IO_F_FAILFAST_DEV		(1U << 8)
>  #define		UBLK_IO_F_FAILFAST_TRANSPORT	(1U << 9)
> @@ -214,6 +224,12 @@ struct ublk_param_discard {
>  	__u16	reserved0;
>  };
>  
> +struct ublk_param_zoned {
> +	__u64	max_open_zones;
> +	__u64	max_active_zones;
> +	__u64	max_append_size;
> +};

Is the above zoned parameter enough for future extension?
Does ZNS need extra parameter? Or some zoned new(important) features?

I highly suggest to reserve some fields for extension, given
it is one ABI interface, which is supposed to be defined well
enough from the beginning.


Thanks, 
Ming