References: <20230224200502.391570-1-nmi@metaspace.dk> <ZAAPBFfqP671N4ue@T590>
User-agent: mu4e 1.9.18; emacs 28.2.50
From:   Andreas Hindborg <nmi@metaspace.dk>
To:     Ming Lei <ming.lei@redhat.com>
Cc:     linux-block@vger.kernel.org, Hans Holmberg <Hans.Holmberg@wdc.com>,
        Matias Bjorling <Matias.Bjorling@wdc.com>,
        Niklas Cassel <Niklas.Cassel@wdc.com>,
        kernel test robot <lkp@intel.com>,
        Jens Axboe <axboe@kernel.dk>,
        open list <linux-kernel@vger.kernel.org>,
        Damien Le Moal <damien.lemoal@opensource.wdc.com>
Subject: Re: [PATCH v2] block: ublk: enable zoned storage support
Date:   Thu, 02 Mar 2023 08:31:07 +0100
In-reply-to: <ZAAPBFfqP671N4ue@T590>
Message-ID: <87o7pblhi1.fsf@metaspace.dk>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk


Hi Ming,

Ming Lei <ming.lei@redhat.com> writes:

> 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.

For ubdsrv, I understand that you prefer to reimplement null and loop targets for
zoned storage. I don't understand why you think this is a good idea,
since we will have massive code duplication. This would be comparable to
having a separate null_blk driver for zoned storage. Am I understanding
you correctly?

Anyway, I think we can discuss the kernel patch even though the ubdsrv
implementation is not a separate target yet? The code would be almost
identical, it would just live in a separate translation unit.

>
>> 
>> 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.

Ok.

>
>> +		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?

I use it to carry information about the first zone of the report request.

>
>> +
>> +		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().

I agree about fetching more zones. However, it is no good to fetch up to
a max, since the requested zone report may less than max. I was
considering overloading req->__data_len and iod->nr_sectors to convey
the number of requested zones. What do you think about that?

>
> 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?

Yes, that should be fine.

>
>> +	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.

I would have to define it as a null pointer in the #else case then?

>
>>  };
>>  
>>  #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.

I see. But do we want to process the requests if BLK_DEV_ZONED is not
enabled, or do we want to fail the IO?

>
>>  	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?

@Damien, @Hans, @Matias, what do you think?

>
> 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.

How many bytes would you reserve?

Thanks!

Best regards,
Andreas