Date:   Fri, 24 Feb 2023 15:53:54 +0000
From:   Niklas Cassel <Niklas.Cassel@....com>
To:     Andreas Hindborg <nmi@...aspace.dk>
CC:     "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        Andreas Hindborg <a.hindborg@...sung.com>,
        Hans Holmberg <Hans.Holmberg@....com>,
        Matias Bjørling <Matias.Bjorling@....com>,
        Ming Lei <ming.lei@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] block: ublk: enable zoned storage support

Hello Andreas,

On Fri, Feb 24, 2023 at 01:59:50PM +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
> 
> Signed-off-by: Andreas Hindborg <a.hindborg@...sung.com>
> ---

Did you try to build this patch with CONFIG_BLK_DEV_ZONED disabled?

I got the following build errors when building it on top of vanilla v6.2
when CONFIG_BLK_DEV_ZONED is disabled:

drivers/block/ublk_drv.c: In function ‘ublk_dev_param_basic_apply’:
drivers/block/ublk_drv.c:221:28: error: ‘struct gendisk’ has no member named ‘nr_zones’
  221 |                 ub->ub_disk->nr_zones = p->dev_sectors / p->chunk_sectors;
      |                            ^~
drivers/block/ublk_drv.c: In function ‘ublk_dev_param_zoned_apply’:
drivers/block/ublk_drv.c:244:17: error: implicit declaration of function ‘disk_set_max_active_zones’; did you mean ‘bdev_max_active_zones’? [-Werror=implicit-function-declaration]
  244 |                 disk_set_max_active_zones(ub->ub_disk, p->max_active_zones);
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~
      |                 bdev_max_active_zones
drivers/block/ublk_drv.c:245:17: error: implicit declaration of function ‘disk_set_max_open_zones’; did you mean ‘bdev_max_open_zones’? [-Werror=implicit-function-declaration]
  245 |                 disk_set_max_open_zones(ub->ub_disk, p->max_open_zones);


>  drivers/block/ublk_drv.c      | 145 ++++++++++++++++++++++++++++++++--
>  include/uapi/linux/ublk_cmd.h |  18 +++++
>  2 files changed, 157 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index 6368b56eacf1..9741b4b1647b 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;
> @@ -212,6 +215,11 @@ 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 (IS_ENABLED(CONFIG_BLK_DEV_ZONED) &&
> +	    ub->dev_info.flags & UBLK_F_ZONED && p->chunk_sectors) {
> +		ub->ub_disk->nr_zones = p->dev_sectors / p->chunk_sectors;
> +	}

Kernel coding style says to not unnecessarily use braces where a single
statement will do:
https://www.kernel.org/doc/html/latest/process/coding-style.html#placing-braces-and-spaces

>  }
>  
>  static void ublk_dev_param_discard_apply(struct ublk_device *ub)
> @@ -227,6 +235,19 @@ static void ublk_dev_param_discard_apply(struct ublk_device *ub)
>  	blk_queue_max_discard_segments(q, p->max_discard_segments);
>  }
>  
> +static void ublk_dev_param_zoned_apply(struct ublk_device *ub)
> +{
> +	const struct ublk_param_zoned *p = &ub->params.zoned;
> +
> +	if (IS_ENABLED(CONFIG_BLK_DEV_ZONED) &&
> +	    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);
> +		/* We do not support zone append yet */
> +		//blk_queue_max_zone_append_sectors(q, zone_size);

Remove commented out code.
It can be added once that feature is added.

> +	}
> +}
> +
>  static int ublk_validate_params(const struct ublk_device *ub)
>  {
>  	/* basic param is the only one which must be set */
> @@ -268,6 +289,9 @@ static int ublk_apply_params(struct ublk_device *ub)
>  	if (ub->params.types & UBLK_PARAM_TYPE_DISCARD)
>  		ublk_dev_param_discard_apply(ub);
>  
> +	if (ub->params.types & UBLK_PARAM_TYPE_ZONED)
> +		ublk_dev_param_zoned_apply(ub);
> +
>  	return 0;
>  }
>  
> @@ -361,9 +385,18 @@ static void ublk_free_disk(struct gendisk *disk)
>  	put_device(&ub->cdev_dev);
>  }
>  
> +#if IS_ENABLED(CONFIG_BLK_DEV_ZONED)

Here you use "#if IS_ENABLED(CONFIG_BLK_DEV_ZONED)"
yet further down you use
"#ifdef CONFIG_BLK_DEV_ZONED".

IS_ENABLED() is usually used when testing for a Kconfig within
a normal C conditional, e.g. if (IS_ENABLED()), where possible,
in order to avoid ugly C preprocessor conditionals completely.

However, if you have to use C preprocessor conditionals, then
#ifdef CONFIG_SOMETHING
is the most common way to conditionally include something.

> +static int ublk_report_zones(struct gendisk *disk, sector_t sector,
> +			     unsigned int nr_zones, report_zones_cb cb,
> +			     void *data);
> +#endif
> +
>  static const struct block_device_operations ub_fops = {
> -	.owner =	THIS_MODULE,
> -	.free_disk =	ublk_free_disk,
> +	.owner = THIS_MODULE,
> +	.free_disk = ublk_free_disk,
> +#if IS_ENABLED(CONFIG_BLK_DEV_ZONED)
> +	.report_zones = ublk_report_zones,
> +#endif
>  };
>  
>  #define UBLK_MAX_PIN_PAGES	32
> @@ -499,7 +532,7 @@ 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 +599,26 @@ 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
>  	default:
>  		return BLK_STS_IOERR;
>  	}
> @@ -612,7 +665,8 @@ 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;
>  	}
> @@ -1493,6 +1547,73 @@ static struct ublk_device *ublk_get_device_from_id(int idx)
>  	return ub;
>  }
>  
> +#ifdef CONFIG_BLK_DEV_ZONED
> +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++) {
> +

No need for empty line here.

> +		struct request *req;
> +		blk_status_t status;
> +		struct blk_zone info;

Since this is allocated on the stack, does it need memset()?

null_blk seems to memset blk_zone before the loop, but not inside the loop:
https://github.com/torvalds/linux/blob/v6.2/drivers/block/null_blk/zoned.c#L206

So I'm a bit confused...

If e.g. cb() is blkdev_copy_zone_to_user()
https://github.com/torvalds/linux/blob/v6.2/block/blk-zoned.c#L318

It will copy whatever the kernel allocated.
So I guess that since you can't guarantee that the ublk user space driver
will fill in all fields in the zone when receiving a REQ_OP_DRV_IN,
I assume that you do need to do a memset() in order to not potentially
leak kernel space data.


> +
> +		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;
> +
> +		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;
> +	}
> +	ret = nr_zones;
> +
> + out:
> +	return ret;
> +}
> +#endif
> +
>  static int ublk_ctrl_start_dev(struct io_uring_cmd *cmd)
>  {
>  	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
> @@ -1535,6 +1656,15 @@ 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 = blk_revalidate_disk_zones(disk, NULL);
> +		if (ret)
> +			goto out_put_disk;
> +	}
> +
>  	get_device(&ub->cdev_dev);
>  	ret = add_disk(disk);
>  	if (ret) {
> @@ -1673,6 +1803,9 @@ 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;
> +};
> +
>  struct ublk_params {
>  	/*
>  	 * Total length of parameters, userspace has to set 'len' for both
> @@ -224,10 +240,12 @@ struct ublk_params {
>  	__u32	len;
>  #define UBLK_PARAM_TYPE_BASIC           (1 << 0)
>  #define UBLK_PARAM_TYPE_DISCARD         (1 << 1)
> +#define UBLK_PARAM_TYPE_ZONED           (1 << 2)
>  	__u32	types;			/* types of parameter included */
>  
>  	struct ublk_param_basic		basic;
>  	struct ublk_param_discard	discard;
> +	struct ublk_param_zoned		zoned;
>  };
>  
>  #endif
> -- 
> 2.39.2
> 

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