Date:   Sat, 8 Jul 2023 22:11:10 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     "Andreas Hindborg (Samsung)" <nmi@...aspace.dk>
Cc:     open list <linux-kernel@...r.kernel.org>,
        "open list:BLOCK LAYER" <linux-block@...r.kernel.org>,
        Minwoo Im <minwoo.im.dev@...il.com>,
        Matias Bjorling <Matias.Bjorling@....com>,
        gost.dev@...sung.com, Jens Axboe <axboe@...nel.dk>,
        Aravind Ramesh <Aravind.Ramesh@....com>,
        Johannes Thumshirn <jth@...nel.org>,
        Hans Holmberg <Hans.Holmberg@....com>,
        Christoph Hellwig <hch@...radead.org>,
        Damien Le Moal <dlemoal@...nel.org>
Subject: Re: [PATCH v6 3/3] ublk: enable zoned storage support

On Fri, Jul 07, 2023 at 05:04:41PM +0200, Andreas Hindborg (Samsung) wrote:
> 
> Ming Lei <ming.lei@...hat.com> writes:
> 
> > On Thu, Jul 06, 2023 at 03:09:30PM +0200, Andreas Hindborg wrote:
> >> From: Andreas Hindborg <a.hindborg@...sung.com>
> >> 
> >> 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
> >>  - REQ_OP_ZONE_APPEND
> >> 
> >> The zone append feature uses the `addr` field of `struct ublksrv_io_cmd` to
> >> communicate ALBA back to the kernel. Therefore ublk must be used with the
> >> user copy feature (UBLK_F_USER_COPY) for zoned storage support to be
> >> available. Without this feature, ublk will not allow zoned storage support.
> >> 
> >> Signed-off-by: Andreas Hindborg <a.hindborg@...sung.com>
> >> ---
> >>  drivers/block/Kconfig         |   4 +
> >>  drivers/block/ublk_drv.c      | 341 ++++++++++++++++++++++++++++++++--
> >>  include/uapi/linux/ublk_cmd.h |  30 +++
> >>  3 files changed, 363 insertions(+), 12 deletions(-)
> >> 
> >> diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
> >> index 5b9d4aaebb81..3f7bedae8511 100644
> >> --- a/drivers/block/Kconfig
> >> +++ b/drivers/block/Kconfig
> >> @@ -373,6 +373,7 @@ config BLK_DEV_RBD
> >>  config BLK_DEV_UBLK
> >>  	tristate "Userspace block driver (Experimental)"
> >>  	select IO_URING
> >> +	select BLK_DEV_UBLK_ZONED if BLK_DEV_ZONED
> >>  	help
> >>  	  io_uring based userspace block driver. Together with ublk server, ublk
> >>  	  has been working well, but interface with userspace or command data
> >> @@ -402,6 +403,9 @@ config BLKDEV_UBLK_LEGACY_OPCODES
> >>  	  suggested to enable N if your application(ublk server) switches to
> >>  	  ioctl command encoding.
> >>  
> >> +config BLK_DEV_UBLK_ZONED
> >> +	bool
> >> +
> >>  source "drivers/block/rnbd/Kconfig"
> >>  
> >>  endif # BLK_DEV
> >> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> >> index 8d271901efac..a5adcfc976a5 100644
> >> --- a/drivers/block/ublk_drv.c
> >> +++ b/drivers/block/ublk_drv.c
> >> @@ -56,22 +56,28 @@
> >>  		| UBLK_F_USER_RECOVERY_REISSUE \
> >>  		| UBLK_F_UNPRIVILEGED_DEV \
> >>  		| UBLK_F_CMD_IOCTL_ENCODE \
> >> -		| UBLK_F_USER_COPY)
> >> +		| UBLK_F_USER_COPY \
> >> +		| UBLK_F_ZONED)
> >>  
> >>  /* All UBLK_PARAM_TYPE_* should be included here */
> >> -#define UBLK_PARAM_TYPE_ALL (UBLK_PARAM_TYPE_BASIC | \
> >> -		UBLK_PARAM_TYPE_DISCARD | UBLK_PARAM_TYPE_DEVT)
> >> +#define UBLK_PARAM_TYPE_ALL                                \
> >> +	(UBLK_PARAM_TYPE_BASIC | UBLK_PARAM_TYPE_DISCARD | \
> >> +	 UBLK_PARAM_TYPE_DEVT | UBLK_PARAM_TYPE_ZONED)
> >>  
> >>  struct ublk_rq_data {
> >>  	struct llist_node node;
> >>  
> >>  	struct kref ref;
> >> +	__u32 operation;
> >> +	__u64 sector;
> >> +	__u32 nr_sectors;
> >>  };
> >
> > Please put "operation" and "nr_sectors" together, then holes
> > can be avoided.
> 
> Got it 👍
> 
> >
> >>  
> >>  struct ublk_uring_cmd_pdu {
> >>  	struct ublk_queue *ubq;
> >>  };
> >>  
> >> +
> >
> > ?
> 
> Sorry.
> 
> >
> >>  /*
> >>   * io command is active: sqe cmd is received, and its cqe isn't done
> >>   *
> >> @@ -110,6 +116,11 @@ struct ublk_uring_cmd_pdu {
> >>   */
> >>  #define UBLK_IO_FLAG_NEED_GET_DATA 0x08
> >>  
> >> +/*
> >> + * Set when IO is Zone Append
> >> + */
> >> +#define UBLK_IO_FLAG_ZONE_APPEND 0x10
> >> +
> >>  struct ublk_io {
> >>  	/* userspace buffer address from io cmd */
> >>  	__u64	addr;
> >> @@ -184,6 +195,31 @@ struct ublk_params_header {
> >>  	__u32	len;
> >>  	__u32	types;
> >>  };
> >> +static inline int ublk_dev_params_zoned(const struct ublk_device *ub)
> >> +{
> >> +	return ub->params.types & UBLK_PARAM_TYPE_ZONED;
> >> +}
> >> +
> >> +static inline bool ublk_dev_is_zoned(const struct ublk_device *ub)
> >> +{
> >> +	return ub->dev_info.flags & UBLK_F_ZONED;
> >> +}
> >> +
> >> +static int ublk_set_nr_zones(struct ublk_device *ub);
> >> +static int ublk_dev_param_zoned_validate(const struct ublk_device *ub);
> >> +static int ublk_dev_param_zoned_apply(struct ublk_device *ub);
> >> +static int ublk_revalidate_disk_zones(struct ublk_device *ub);
> >> +
> >> +#ifndef CONFIG_BLK_DEV_UBLK_ZONED
> >> +
> >> +#define ublk_report_zones (NULL)
> >> +
> >> +#else
> >> +
> >> +static int ublk_report_zones(struct gendisk *disk, sector_t sector,
> >> +		      unsigned int nr_zones, report_zones_cb cb, void *data);
> >> +
> >> +#endif
> >
> > Please merge the following "#ifdef CONFIG_BLK_DEV_UBLK_ZONED" with the
> > above one, then you can avoid the above declarations. Meantime, we don't
> > add code after MODULE_LICENSE().
> 
> Ok 👍
> 
> >
> >>  
> >>  static inline bool ublk_dev_is_user_copy(const struct ublk_device *ub)
> >>  {
> >> @@ -232,7 +268,7 @@ static inline unsigned ublk_pos_to_tag(loff_t pos)
> >>  		UBLK_TAG_BITS_MASK;
> >>  }
> >>  
> >> -static void ublk_dev_param_basic_apply(struct ublk_device *ub)
> >> +static int ublk_dev_param_basic_apply(struct ublk_device *ub)
> >>  {
> >>  	struct request_queue *q = ub->ub_disk->queue;
> >>  	const struct ublk_param_basic *p = &ub->params.basic;
> >> @@ -257,6 +293,11 @@ 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 (ublk_dev_is_zoned(ub))
> >> +		return ublk_set_nr_zones(ub);
> >> +
> >
> > The above change can be moved into ublk_dev_param_zoned_apply() which
> > is always done after ublk_dev_param_basic_apply(). 
> 
> Ok
> 
> >
> >> +	return 0;
> >>  }
> >>  
> >>  static void ublk_dev_param_discard_apply(struct ublk_device *ub)
> >> @@ -286,6 +327,9 @@ static int ublk_validate_params(const struct ublk_device *ub)
> >>  
> >>  		if (p->max_sectors > (ub->dev_info.max_io_buf_bytes >> 9))
> >>  			return -EINVAL;
> >> +
> >> +		if (ublk_dev_is_zoned(ub) && !p->chunk_sectors)
> >> +			return -EINVAL;
> >>  	} else
> >>  		return -EINVAL;
> >>  
> >> @@ -304,19 +348,26 @@ static int ublk_validate_params(const struct ublk_device *ub)
> >>  	if (ub->params.types & UBLK_PARAM_TYPE_DEVT)
> >>  		return -EINVAL;
> >>  
> >> -	return 0;
> >> +	return ublk_dev_param_zoned_validate(ub);
> >
> > Please follow current style of:
> >
> > 	if (ub->params.types & UBLK_PARAM_TYPE_ZONED)
> > 		return ublk_dev_param_zoned_validate(ub);
> >
> > Then you can avoid lots of check on ublk_dev_params_zoned().
> 
> Ok, but then I need
> 
> 
> 	if (ublk_dev_is_zoned(ub) && !ublk_dev_params_zoned(ub))
> 		return -EINVAL;
> 
> here to check if user is forgetting zoned parameters for zoned ublk dev.
> Or do you want to drop this check?

OK, zoned is a bit special, then you still can do it:

 	if (ub->params.types & UBLK_PARAM_TYPE_ZONED)
 		return ublk_dev_param_zoned_validate(ub);
	else if (ublk_dev_is_zoned(ub))
		return -EINVAL;

which is more readable.

> 
> >
> >>  }
> >>  
> >>  static int ublk_apply_params(struct ublk_device *ub)
> >>  {
> >> +	int ret;
> >> +
> >>  	if (!(ub->params.types & UBLK_PARAM_TYPE_BASIC))
> >>  		return -EINVAL;
> >>  
> >> -	ublk_dev_param_basic_apply(ub);
> >> +	ret = ublk_dev_param_basic_apply(ub);
> >> +	if (ret)
> >> +		return ret;
> >>  
> >>  	if (ub->params.types & UBLK_PARAM_TYPE_DISCARD)
> >>  		ublk_dev_param_discard_apply(ub);
> >>  
> >> +	if (ublk_dev_params_zoned(ub))
> >> +		return ublk_dev_param_zoned_apply(ub);
> >> +
> >>  	return 0;
> >>  }
> >>  
> >> @@ -487,6 +538,7 @@ static const struct block_device_operations ub_fops = {
> >>  	.owner =	THIS_MODULE,
> >>  	.open =		ublk_open,
> >>  	.free_disk =	ublk_free_disk,
> >> +	.report_zones =	ublk_report_zones,
> >>  };
> >>  
> >>  #define UBLK_MAX_PIN_PAGES	32
> >> @@ -601,7 +653,8 @@ static inline bool ublk_need_map_req(const struct request *req)
> >>  
> >>  static inline bool ublk_need_unmap_req(const struct request *req)
> >>  {
> >> -	return ublk_rq_has_data(req) && req_op(req) == REQ_OP_READ;
> >> +	return ublk_rq_has_data(req) &&
> >> +	       (req_op(req) == REQ_OP_READ || req_op(req) == REQ_OP_DRV_IN);
> >>  }
> >>  
> >>  static int ublk_map_io(const struct ublk_queue *ubq, const struct request *req,
> >> @@ -685,6 +738,7 @@ static blk_status_t ublk_setup_iod(struct ublk_queue *ubq, struct request *req)
> >>  {
> >>  	struct ublksrv_io_desc *iod = ublk_get_iod(ubq, req->tag);
> >>  	struct ublk_io *io = &ubq->ios[req->tag];
> >> +	struct ublk_rq_data *pdu = blk_mq_rq_to_pdu(req);
> >>  	u32 ublk_op;
> >>  
> >>  	switch (req_op(req)) {
> >> @@ -703,6 +757,37 @@ 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;
> >> +	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 = pdu->operation;
> >> +		switch (ublk_op) {
> >> +		case UBLK_IO_OP_REPORT_ZONES:
> >> +			iod->op_flags = ublk_op | ublk_req_build_flags(req);
> >> +			iod->nr_sectors = pdu->nr_sectors;
> >> +			iod->start_sector = pdu->sector;
> >> +			return BLK_STS_OK;
> >> +		default:
> >> +			return BLK_STS_IOERR;
> >> +		}
> >> +	case REQ_OP_ZONE_APPEND:
> >> +		ublk_op = UBLK_IO_OP_ZONE_APPEND;
> >> +		io->flags |= UBLK_IO_FLAG_ZONE_APPEND;
> >> +		break;
> >> +	case REQ_OP_ZONE_RESET_ALL:
> >
> > BLK_STS_NOTSUPP should be returned, since in future we may support it,
> > and userspace need to know what is wrong.
> 
> Ok
> 
> >
> >> +	case REQ_OP_DRV_OUT:
> >> +		/* We do not support reset_all and drv_out */
> >> +		fallthrough;
> >>  	default:
> >>  		return BLK_STS_IOERR;
> >>  	}
> >> @@ -756,7 +841,8 @@ static inline 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)
> >>  		goto exit;
> >>  
> >>  	/* for READ request, writing data in iod->addr to rq buffers */
> >> @@ -1120,6 +1206,11 @@ static void ublk_commit_completion(struct ublk_device *ub,
> >>  	/* find the io request and complete */
> >>  	req = blk_mq_tag_to_rq(ub->tag_set.tags[qid], tag);
> >>  
> >> +	if (io->flags & UBLK_IO_FLAG_ZONE_APPEND) {
> >> +		req->__sector = ub_cmd->addr;
> >> +		io->flags &= ~UBLK_IO_FLAG_ZONE_APPEND;
> >> +	}
> >> +
> >>  	if (req && likely(!blk_should_fake_timeout(req->q)))
> >>  		ublk_put_req_ref(ubq, req);
> >>  }
> >> @@ -1419,7 +1510,8 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
> >>  			^ (_IOC_NR(cmd_op) == UBLK_IO_NEED_GET_DATA))
> >>  		goto out;
> >>  
> >> -	if (ublk_support_user_copy(ubq) && ub_cmd->addr) {
> >> +	if (ublk_support_user_copy(ubq) &&
> >> +	    !(io->flags & UBLK_IO_FLAG_ZONE_APPEND) && ub_cmd->addr) {
> >>  		ret = -EINVAL;
> >>  		goto out;
> >>  	}
> >> @@ -1542,11 +1634,14 @@ static inline bool ublk_check_ubuf_dir(const struct request *req,
> >>  		int ubuf_dir)
> >>  {
> >>  	/* copy ubuf to request pages */
> >> -	if (req_op(req) == REQ_OP_READ && ubuf_dir == ITER_SOURCE)
> >> +	if ((req_op(req) == REQ_OP_READ || req_op(req) == REQ_OP_DRV_IN) &&
> >> +	    ubuf_dir == ITER_SOURCE)
> >>  		return true;
> >>  
> >>  	/* copy request pages to ubuf */
> >> -	if (req_op(req) == REQ_OP_WRITE && ubuf_dir == ITER_DEST)
> >> +	if ((req_op(req) == REQ_OP_WRITE ||
> >> +	     req_op(req) == REQ_OP_ZONE_APPEND) &&
> >> +	    ubuf_dir == ITER_DEST)
> >>  		return true;
> >>  
> >>  	return false;
> >> @@ -1883,8 +1978,12 @@ static int ublk_ctrl_start_dev(struct ublk_device *ub, struct io_uring_cmd *cmd)
> >>  	if (ub->nr_privileged_daemon != ub->nr_queues_ready)
> >>  		set_bit(GD_SUPPRESS_PART_SCAN, &disk->state);
> >>  
> >> -	get_device(&ub->cdev_dev);
> >>  	ub->dev_info.state = UBLK_S_DEV_LIVE;
> >> +	ret = ublk_revalidate_disk_zones(ub);
> >> +	if (ret)
> >> +		goto out_put_disk;
> >> +
> >> +	get_device(&ub->cdev_dev);
> >>  	ret = add_disk(disk);
> >>  	if (ret) {
> >>  		/*
> >> @@ -2045,6 +2144,13 @@ static int ublk_ctrl_add_dev(struct io_uring_cmd *cmd)
> >>  	if (ublk_dev_is_user_copy(ub))
> >>  		ub->dev_info.flags &= ~UBLK_F_NEED_GET_DATA;
> >>  
> >> +	/* Zoned storage support requires user copy feature */
> >> +	if (ublk_dev_is_zoned(ub) &&
> >> +	    (!IS_ENABLED(CONFIG_BLK_DEV_UBLK_ZONED) || !ublk_dev_is_user_copy(ub))) {
> >> +		ret = -EINVAL;
> >> +		goto out_free_dev_number;
> >> +	}
> >> +
> >>  	/* We are not ready to support zero copy */
> >>  	ub->dev_info.flags &= ~UBLK_F_SUPPORT_ZERO_COPY;
> >>  
> >> @@ -2629,3 +2735,214 @@ MODULE_PARM_DESC(ublks_max, "max number of ublk devices allowed to add(default:
> >>  
> >>  MODULE_AUTHOR("Ming Lei <ming.lei@...hat.com>");
> >>  MODULE_LICENSE("GPL");
> >> +
> >> +#ifdef CONFIG_BLK_DEV_UBLK_ZONED
> >> +
> >> +static int get_nr_zones(const struct ublk_device *ub)
> >> +{
> >> +	const struct ublk_param_basic *p = &ub->params.basic;
> >> +
> >> +	if (!p->chunk_sectors)
> >> +		return 0;
> >
> > There isn't zoned device if the above check fails, so no
> > need to check it.
> 
> Ok, but this is called from `ublk_dev_param_zoned_validate()` to
> validate user sets params correct. Should we not report error to user
> space during parameter validation if user space sets chunk_sectors to
> zero for zoned device?

That has been covered in UBLK_PARAM_TYPE_BASIC branch of ublk_validate_params().

> 
> >
> >> +
> >> +	/* Zone size is a power of 2 */
> >> +	return p->dev_sectors >> ilog2(p->chunk_sectors);
> >> +}
> >> +
> >> +static int ublk_set_nr_zones(struct ublk_device *ub)
> >> +{
> >> +	ub->ub_disk->nr_zones = get_nr_zones(ub);
> >> +	if (!ub->ub_disk->nr_zones)
> >> +		return -EINVAL;
> >
> > Is nr_zones one must for zoned?
> 
> Zero zones for a zoned storage device is not allowed, as far as I am
> aware. Am I mistaken?

OK, never mind, I just didn't see such check in null zoned and virtio-blk.

> 
> >
> >> +
> >> +	return 0;
> >> +}
> >> +
> >> +static int ublk_revalidate_disk_zones(struct ublk_device *ub)
> >> +{
> >> +	if (ublk_dev_is_zoned(ub))
> >> +		return blk_revalidate_disk_zones(ub->ub_disk, NULL);
> >> +
> >> +	return 0;
> >> +}
> >> +
> >> +static int ublk_dev_param_zoned_validate(const struct ublk_device *ub)
> >> +{
> >> +	const struct ublk_param_zoned *p = &ub->params.zoned;
> >> +	int nr_zones;
> >> +
> >> +	if (ublk_dev_is_zoned(ub) && !ublk_dev_params_zoned(ub))
> >> +		return -EINVAL;
> >> +
> >> +	if (!ublk_dev_is_zoned(ub) && ublk_dev_params_zoned(ub))
> >> +		return -EINVAL;
> >> +
> >> +	if (!ublk_dev_params_zoned(ub))
> >> +		return 0;
> >
> > The above can be simplified as single check if we follow current
> > validate/apply code style:
> >
> > 	if (!ublk_dev_is_zoned(ub))
> > 		return -EINVAL;
> 
> If we do that we will not be able to check if user space sets the
> `UBLK_F_ZONED` flag without setting zoned parameters. Should I validate
> that at call site or drop the check?

Please see above comment, which can be covered as:

 	if (ub->params.types & UBLK_PARAM_TYPE_ZONED)
 		return ublk_dev_param_zoned_validate(ub);
	else if (ublk_dev_is_zoned(ub))
		return -EINVAL;

> 
> >> +
> >> +	if (!p->max_zone_append_sectors)
> >> +		return -EINVAL;
> >> +
> >> +	nr_zones = get_nr_zones(ub);
> >> +
> >> +	if (p->max_active_zones > nr_zones)
> >> +		return -EINVAL;
> >> +
> >> +	if (p->max_open_zones > nr_zones)
> >> +		return -EINVAL;
> >> +
> >> +	return 0;
> >> +}
> >> +
> >> +static int ublk_dev_param_zoned_apply(struct ublk_device *ub)
> >> +{
> >> +	const struct ublk_param_zoned *p = &ub->params.zoned;
> >> +
> >> +	disk_set_zoned(ub->ub_disk, BLK_ZONED_HM);
> >> +	blk_queue_required_elevator_features(ub->ub_disk->queue,
> >> +					     ELEVATOR_F_ZBD_SEQ_WRITE);
> >> +	disk_set_max_active_zones(ub->ub_disk, p->max_active_zones);
> >> +	disk_set_max_open_zones(ub->ub_disk, p->max_open_zones);
> >> +	blk_queue_max_zone_append_sectors(ub->ub_disk->queue, p->max_zone_append_sectors);
> >> +
> >> +	return 0;
> >> +}
> >> +
> >> +/* Based on virtblk_alloc_report_buffer */
> >> +static void *ublk_alloc_report_buffer(struct ublk_device *ublk,
> >> +				      unsigned int nr_zones, size_t *buflen)
> >> +{
> >> +	struct request_queue *q = ublk->ub_disk->queue;
> >> +	size_t bufsize;
> >> +	void *buf;
> >> +
> >> +	nr_zones = min_t(unsigned int, nr_zones,
> >> +			 ublk->ub_disk->nr_zones);
> >> +
> >> +	bufsize = nr_zones * sizeof(struct blk_zone);
> >> +	bufsize =
> >> +		min_t(size_t, bufsize, queue_max_hw_sectors(q) << SECTOR_SHIFT);
> >> +	bufsize = min_t(size_t, bufsize, queue_max_segments(q) << PAGE_SHIFT);
> >> +
> >> +	while (bufsize >= sizeof(struct blk_zone)) {
> >> +		buf = __vmalloc(bufsize, GFP_KERNEL | __GFP_NORETRY);
> >> +		if (buf) {
> >> +			*buflen = bufsize;
> >> +			return buf;
> >> +		}
> >> +		bufsize >>= 1;
> >> +	}
> >> +
> >> +	*buflen = 0;
> >> +	return 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 = disk->private_data;
> >> +	unsigned int zone_size_sectors = disk->queue->limits.chunk_sectors;
> >> +	unsigned int first_zone = sector >> ilog2(zone_size_sectors);
> >> +	unsigned int done_zones = 0;
> >> +	unsigned int max_zones_per_request;
> >> +	int ret;
> >> +	struct blk_zone *buffer;
> >> +	size_t buffer_length;
> >> +
> >> +	if (!ublk_dev_is_zoned(ub))
> >> +		return -EOPNOTSUPP;
> >> +
> >> +	nr_zones = min_t(unsigned int, ub->ub_disk->nr_zones - first_zone,
> >> +			 nr_zones);
> >> +
> >> +	buffer = ublk_alloc_report_buffer(ub, nr_zones, &buffer_length);
> >> +	if (!buffer)
> >> +		return -ENOMEM;
> >> +
> >> +	max_zones_per_request = buffer_length / sizeof(struct blk_zone);
> >> +
> >> +	while (done_zones < nr_zones) {
> >> +		unsigned int remaining_zones = nr_zones - done_zones;
> >> +		unsigned int zones_in_request =
> >> +			min_t(unsigned int, remaining_zones, max_zones_per_request);
> >> +		struct request *req;
> >> +		struct ublk_rq_data *pdu;
> >> +		blk_status_t status;
> >> +
> >> +		memset(buffer, 0, buffer_length);
> >> +
> >> +		req = blk_mq_alloc_request(disk->queue, REQ_OP_DRV_IN, 0);
> >> +		if (IS_ERR(req)) {
> >> +			ret = PTR_ERR(req);
> >> +			goto out;
> >> +		}
> >> +
> >> +		pdu = blk_mq_rq_to_pdu(req);
> >> +		pdu->operation = UBLK_IO_OP_REPORT_ZONES;
> >> +		pdu->sector = sector;
> >> +		pdu->nr_sectors = remaining_zones * zone_size_sectors;
> >> +
> >> +		ret = blk_rq_map_kern(disk->queue, req, buffer, buffer_length,
> >> +					GFP_KERNEL);
> >> +		if (ret) {
> >> +			blk_mq_free_request(req);
> >> +			goto out;
> >> +		}
> >> +
> >> +		status = blk_execute_rq(req, 0);
> >> +		ret = blk_status_to_errno(status);
> >> +		blk_mq_free_request(req);
> >> +		if (ret)
> >> +			goto out;
> >> +
> >> +		for (unsigned int i = 0; i < zones_in_request; i++) {
> >> +			struct blk_zone *zone = buffer + i;
> >> +
> >> +			/* A zero length zone means no more zones in this response */
> >> +			if (!zone->len)
> >> +				break;
> >> +
> >> +			ret = cb(zone, i, data);
> >> +			if (ret)
> >> +				goto out;
> >> +
> >> +			done_zones++;
> >> +			sector += zone_size_sectors;
> >> +
> >> +		}
> >> +	}
> >> +
> >> +	ret = done_zones;
> >> +
> >> +out:
> >> +	kvfree(buffer);
> >> +	return ret;
> >> +}
> >> +
> >> +#else
> >> +
> >> +static int ublk_set_nr_zones(struct ublk_device *ub)
> >> +{
> >> +	return 0;
> >> +}
> >> +
> >> +static int ublk_dev_param_zoned_validate(const struct ublk_device *ub)
> >> +{
> >> +	if (ublk_dev_params_zoned(ub))
> >> +		return -EINVAL;
> >> +	return 0;
> >
> > Please move the check outside by following current code style, then:
> >
> > 		return -EINVAL;
> >
> 
> Ok, but then we move the check for user applying zoned params to
> non-zoned device when CONFIG_BLK_DEV_ZONED to call site?

Yes, the point is to move check in common code, then not only reduce
repeated check, but also cleaner.


Thanks, 
Ming

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