Re: [PATCH 2/2] block: add BLKSETDESCZONE ioctl for Zoned Block Devices

[Damien Le Moal]

On 2020/06/29 8:01, Matias Bjorling wrote:
> The NVMe Zoned Namespace Command Set adds support for associating
> data to a zone through the Zone Descriptor Extension feature.
> 
> To allow user-space to associate data to a zone, add support through
> the BLKSETDESCZONE ioctl. The ioctl requires that it is issued to
> a zoned block device, and that it supports the Zone Descriptor
> Extension feature. Support is detected through the
> the zone_desc_ext_bytes sysfs queue entry for the specific block
> device. A value larger than zero communicates that the device supports
> the feature.
> 
> The ioctl associates data to a zone by issuing a Zone Management Send
> command with the Zone Send Action set as the Set Zone Descriptor
> Extension.
> 
> For the command to complete successfully, the specified zone must be
> in the Empty state, and active resources must be available. On
> success, the specified zone is transioned to Closed state by the
> device. If less data is supplied by user-space then reported by the
> the Zone Descriptor Extension size, the rest is zero-filled. If more
> data or no data is supplied by user-space, the ioctl fails.
> 
> To issue the ioctl, a new blk_zone_set_desc data structure is defined.
> It has following parameters:
> 
>  * the sector of the specific zone.
>  * the length of the data to be associated to the zone.
>  * any flags be used by the ioctl. None is defined.
>  * data associated to the zone.
> 
> The data is laid out after the flags parameter, and it is the caller's
> responsibility to allocate memory for the data that is specified in the
> length parameter.
> 
> Signed-off-by: Matias Bjørling <matias.bjorling@xxxxxxx>
> ---
>  block/blk-zoned.c             | 108 ++++++++++++++++++++++++++++++++++
>  block/ioctl.c                 |   2 +
>  drivers/nvme/host/core.c      |   3 +
>  drivers/nvme/host/nvme.h      |   9 +++
>  drivers/nvme/host/zns.c       |  11 ++++
>  include/linux/blk_types.h     |   2 +
>  include/linux/blkdev.h        |   9 ++-
>  include/uapi/linux/blkzoned.h |  20 ++++++-
>  8 files changed, 162 insertions(+), 2 deletions(-)
> 
> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> index 81152a260354..4dc40ec006a2 100644
> --- a/block/blk-zoned.c
> +++ b/block/blk-zoned.c
> @@ -259,6 +259,50 @@ int blkdev_zone_mgmt(struct block_device *bdev, enum req_opf op,
>  }
>  EXPORT_SYMBOL_GPL(blkdev_zone_mgmt);
>  
> +/**
> + * blkdev_zone_set_desc - Execute a zone management set zone descriptor
> + *                        extension operation on a zone
> + * @bdev:	Target block device
> + * @sector:	Start sector of the zone to operate on
> + * @data:	Pointer to the data that is to be associated to the zone
> + * @gfp_mask:	Memory allocation flags (for bio_alloc)
> + *
> + * Description:
> + *    Associate zone descriptor extension data to a specified zone.
> + *    The block device must support zone descriptor extensions.
> + *    i.e., by exposing a positive zone descriptor extension size.
> + */
> +int blkdev_zone_set_desc(struct block_device *bdev, sector_t sector,
> +			 struct page *data, gfp_t gfp_mask)

struct page for the data ? Why not just a "void *" to allow for kmalloc/vmalloc
data ? And no length for the data ? This is a bit odd.

> +{
> +	struct request_queue *q = bdev_get_queue(bdev);
> +	sector_t zone_sectors = blk_queue_zone_sectors(q);
> +	struct bio_vec bio_vec;
> +	struct bio bio;
> +
> +	if (!blk_queue_is_zoned(q))
> +		return -EOPNOTSUPP;
> +
> +	if (bdev_read_only(bdev))
> +		return -EPERM;

You are not checking the zone_desc_ext_bytes limit here. You should.
> +
> +	/* Check alignment (handle eventual smaller last zone) */
> +	if (sector & (zone_sectors - 1))
> +		return -EINVAL;

The comment is incorrect. There is nothing special for handling the last zone in
this test.

> +
> +	bio_init(&bio, &bio_vec, 1);
> +	bio.bi_opf = REQ_OP_ZONE_SET_DESC | REQ_SYNC;
> +	bio.bi_iter.bi_sector = sector;
> +	bio_set_dev(&bio, bdev);
> +	bio_add_page(&bio, data, queue_zone_desc_ext_bytes(q), 0);
> +
> +	/* This may take a while, so be nice to others */
> +	cond_resched();

This is not a loop, so you do not need this.

> +
> +	return submit_bio_wait(&bio);
> +}
> +EXPORT_SYMBOL_GPL(blkdev_zone_set_desc);
> +
>  struct zone_report_args {
>  	struct blk_zone __user *zones;
>  };
> @@ -370,6 +414,70 @@ int blkdev_zone_mgmt_ioctl(struct block_device *bdev, fmode_t mode,
>  				GFP_KERNEL);
>  }
>  
> +/*
> + * BLKSETDESCZONE ioctl processing.
> + * Called from blkdev_ioctl.
> + */
> +int blkdev_zone_set_desc_ioctl(struct block_device *bdev, fmode_t mode,
> +			       unsigned int cmd, unsigned long arg)
> +{
> +	void __user *argp = (void __user *)arg;
> +	struct request_queue *q;
> +	struct blk_zone_set_desc zsd;
> +	void *zsd_data;
> +	int ret;
> +
> +	if (!argp)
> +		return -EINVAL;
> +
> +	q = bdev_get_queue(bdev);
> +	if (!q)
> +		return -ENXIO;
> +
> +	if (!blk_queue_is_zoned(q))
> +		return -ENOTTY;
> +
> +	if (!capable(CAP_SYS_ADMIN))
> +		return -EACCES;
> +
> +	if (!(mode & FMODE_WRITE))
> +		return -EBADF;
> +
> +	if (!queue_zone_desc_ext_bytes(q))
> +		return -EOPNOTSUPP;
> +
> +	if (copy_from_user(&zsd, argp, sizeof(struct blk_zone_set_desc)))
> +		return -EFAULT;
> +
> +	/* no flags is currently supported */
> +	if (zsd.flags)
> +		return -ENOTTY;
> +
> +	if (!zsd.len || zsd.len > queue_zone_desc_ext_bytes(q))
> +		return -ENOTTY;

This should go into blkdev_zone_set_desc() as well so that in-kernel users are
checked. So there may be no need to check this here.

> +
> +	/* allocate the size of the zone descriptor extension and fill
> +	 * with the data in the user data buffer. If the data size is less
> +	 * than the zone descriptor extension size, then the rest of the
> +	 * zone description extension data buffer is zero-filled.
> +	 */
> +	zsd_data = (void *) get_zeroed_page(GFP_KERNEL);
> +	if (!zsd_data)
> +		return -ENOMEM;
> +
> +	if (copy_from_user(zsd_data, argp + sizeof(struct blk_zone_set_desc),
> +			   zsd.len)) {
> +		ret = -EFAULT;
> +		goto free;
> +	}
> +
> +	ret = blkdev_zone_set_desc(bdev, zsd.sector, virt_to_page(zsd_data),
> +	      GFP_KERNEL);
> +free:
> +	free_page((unsigned long) zsd_data);
> +	return ret;
> +}
> +
>  static inline unsigned long *blk_alloc_zone_bitmap(int node,
>  						   unsigned int nr_zones)
>  {
> diff --git a/block/ioctl.c b/block/ioctl.c
> index bdb3bbb253d9..b9744705835b 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -515,6 +515,8 @@ static int blkdev_common_ioctl(struct block_device *bdev, fmode_t mode,
>  	case BLKCLOSEZONE:
>  	case BLKFINISHZONE:
>  		return blkdev_zone_mgmt_ioctl(bdev, mode, cmd, arg);
> +	case BLKSETDESCZONE:
> +		return blkdev_zone_set_desc_ioctl(bdev, mode, cmd, arg);
>  	case BLKGETZONESZ:
>  		return put_uint(argp, bdev_zone_sectors(bdev));
>  	case BLKGETNRZONES:
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index e961910da4ac..b8f25b0d00ad 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_SET_DESC:
> +		ret = nvme_setup_zone_set_desc(ns, req, cmd);
> +		break;
>  	case REQ_OP_WRITE_ZEROES:
>  		ret = nvme_setup_write_zeroes(ns, req, cmd);
>  		break;
> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
> index 662f95fbd909..5bd5a437b038 100644
> --- a/drivers/nvme/host/nvme.h
> +++ b/drivers/nvme/host/nvme.h
> @@ -708,6 +708,9 @@ int nvme_report_zones(struct gendisk *disk, sector_t sector,
>  blk_status_t nvme_setup_zone_mgmt_send(struct nvme_ns *ns, struct request *req,
>  				       struct nvme_command *cmnd,
>  				       enum nvme_zone_mgmt_action action);
> +
> +blk_status_t nvme_setup_zone_set_desc(struct nvme_ns *ns, struct request *req,
> +				       struct nvme_command *cmnd);
>  #else
>  #define nvme_report_zones NULL
>  
> @@ -718,6 +721,12 @@ static inline blk_status_t nvme_setup_zone_mgmt_send(struct nvme_ns *ns,
>  	return BLK_STS_NOTSUPP;
>  }
>  
> +static inline blk_status_t nvme_setup_zone_set_desc(struct nvme_ns *ns,
> +		struct request *req, struct nvme_command *cmnd)
> +{
> +	return BLK_STS_NOTSUPP;
> +}
> +
>  static inline int nvme_update_zone_info(struct gendisk *disk,
>  					struct nvme_ns *ns,
>  					unsigned lbaf)
> diff --git a/drivers/nvme/host/zns.c b/drivers/nvme/host/zns.c
> index 5792d953a8f3..bfa64cc685d3 100644
> --- a/drivers/nvme/host/zns.c
> +++ b/drivers/nvme/host/zns.c
> @@ -239,3 +239,14 @@ blk_status_t nvme_setup_zone_mgmt_send(struct nvme_ns *ns, struct request *req,
>  
>  	return BLK_STS_OK;
>  }
> +
> +blk_status_t nvme_setup_zone_set_desc(struct nvme_ns *ns, struct request *req,
> +		struct nvme_command *c)
> +{
> +	c->zms.opcode = nvme_cmd_zone_mgmt_send;
> +	c->zms.nsid = cpu_to_le32(ns->head->ns_id);
> +	c->zms.slba = cpu_to_le64(nvme_sect_to_lba(ns, blk_rq_pos(req)));
> +	c->zms.action = NVME_ZONE_SET_DESC_EXT;
> +
> +	return BLK_STS_OK;
> +}
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index ccb895f911b1..53b7b05b0004 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,
> +	/* associate zone desc extension data to a zone */
> +	REQ_OP_ZONE_SET_DESC	= 14,
>  
>  	/* SCSI passthrough using struct scsi_request */
>  	REQ_OP_SCSI_IN		= 32,
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 2ed55055f68d..c5f092dd5aa3 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -370,7 +370,8 @@ extern int blkdev_report_zones_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);
> -
> +extern int blkdev_zone_set_desc_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)
> @@ -392,6 +393,12 @@ static inline int blkdev_zone_mgmt_ioctl(struct block_device *bdev,
>  	return -ENOTTY;
>  }
>  
> +static inline int blkdev_zone_set_desc_ioctl(struct block_device *bdev,
> +					     fmode_t mode, unsigned int cmd,
> +					     unsigned long arg)
> +{
> +	return -ENOTTY;
> +}
>  #endif /* CONFIG_BLK_DEV_ZONED */
>  
>  struct request_queue {
> diff --git a/include/uapi/linux/blkzoned.h b/include/uapi/linux/blkzoned.h
> index 42c3366cc25f..68abda9abf33 100644
> --- a/include/uapi/linux/blkzoned.h
> +++ b/include/uapi/linux/blkzoned.h
> @@ -142,6 +142,20 @@ struct blk_zone_range {
>  	__u64		nr_sectors;
>  };
>  
> +/**
> + * struct blk_zone_set_desc - BLKSETDESCZONE ioctl requests
> + * @sector: Starting sector of the zone to operate on.
> + * @flags: Feature flags.
> + * @len: size, in bytes, of the data to be associated to the zone.
> + * @data: data to be associated.
> + */
> +struct blk_zone_set_desc {
> +	__u64		sector;
> +	__u32		flags;
> +	__u32		len;
> +	__u8		data[0];
> +};
> +
>  /**
>   * Zoned block device ioctl's:
>   *
> @@ -158,6 +172,10 @@ struct blk_zone_range {
>   *                The 512 B sector range must be zone aligned.
>   * @BLKFINISHZONE: Mark the zones as full in the specified sector range.
>   *                 The 512 B sector range must be zone aligned.
> + * @BLKSETDESCZONE: Set zone description extension data for the zone
> + *                  in the specified sector. On success, the zone
> + *                  will transition to the closed zone state.
> + *                  The 512B sector must be zone aligned.
>   */
>  #define BLKREPORTZONE	_IOWR(0x12, 130, struct blk_zone_report)
>  #define BLKRESETZONE	_IOW(0x12, 131, struct blk_zone_range)
> @@ -166,5 +184,5 @@ struct blk_zone_range {
>  #define BLKOPENZONE	_IOW(0x12, 134, struct blk_zone_range)
>  #define BLKCLOSEZONE	_IOW(0x12, 135, struct blk_zone_range)
>  #define BLKFINISHZONE	_IOW(0x12, 136, struct blk_zone_range)
> -
> +#define BLKSETDESCZONE	_IOW(0x12, 137, struct blk_zone_set_desc)
>  #endif /* _UAPI_BLKZONED_H */
> 

How to you retreive an extended descriptor that was set ? I do not see any code
doing that. Report zones is not changed, but I would leave that one as is and
implement a BLKGETDESCZONE ioctl & in-kernel API.

-- 
Damien Le Moal
Western Digital Research