Message-ID: <871qhbxa0m.fsf@metaspace.dk>
Date:   Thu, 13 Jul 2023 08:41:33 +0200
From:   "Andreas Hindborg (Samsung)" <nmi@...aspace.dk>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     Hans Holmberg <Hans.Holmberg@....com>,
        Jens Axboe <axboe@...nel.dk>,
        Matias Bjorling <Matias.Bjorling@....com>,
        "open list:BLOCK LAYER" <linux-block@...r.kernel.org>,
        Christoph Hellwig <hch@...radead.org>, gost.dev@...sung.com,
        open list <linux-kernel@...r.kernel.org>,
        Aravind Ramesh <Aravind.Ramesh@....com>,
        Damien Le Moal <dlemoal@...nel.org>,
        Minwoo Im <minwoo.im.dev@...il.com>,
        Johannes Thumshirn <jth@...nel.org>
Subject: Re: [PATCH v8 2/2] ublk: enable zoned storage support


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

> On Tue, Jul 11, 2023 at 09:23:53AM +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.
>
> Without one userspace implementation, it is hard to verify the kernel
> change, so I write one zoned target example based on libublk-rs by
> taking one day.
>
> https://github.com/ming1/libublk-rs.git [1]
>
> It is one zoned-ramdisk example, and should be easy to
> add persistence zoned. All zoned commands are covered, except for
> REQ_OP_ZONE_RESET_ALL.
>
> How to create ublk-zoned:
>
> 	cargo run --example zoned -- add -1 1024   #1024MB
>
> So far it passes all blktests/zbd tests for external zoned device.
>
> 'mkfs.btrfs -O zoned' & mount & git clone linux_kernel in this btrfs
> works.
>
> So this patchset gets verified now, so far so good.

Thanks, that is really awesome! I have been testing with a patched
version of ubdsrv. It's nice to get some more test coverage options.

>
> [1] not publish to crates.io yet, still need some cleanup
>
>> 
>> Signed-off-by: Andreas Hindborg <a.hindborg@...sung.com>
>> ---
>>  drivers/block/ublk_drv.c      | 314 ++++++++++++++++++++++++++++++++--
>>  include/uapi/linux/ublk_cmd.h |  36 +++-
>>  2 files changed, 331 insertions(+), 19 deletions(-)
>> 
>> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
>> index 8d271901efac..a57be961b708 100644
>> --- a/drivers/block/ublk_drv.c
>> +++ b/drivers/block/ublk_drv.c
>> @@ -56,16 +56,21 @@
>>  		| 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;
>> +	__u64 sector;
>> +	__u32 operation;
>> +	__u32 nr_sectors;
>>  };
>>  
>>  struct ublk_uring_cmd_pdu {
>> @@ -110,6 +115,11 @@ 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;
>> @@ -190,6 +200,198 @@ static inline bool ublk_dev_is_user_copy(const struct ublk_device *ub)
>>  	return ub->dev_info.flags & UBLK_F_USER_COPY;
>>  }
>>  
>> +static inline bool ublk_dev_is_zoned(const struct ublk_device *ub)
>> +{
>> +	return ub->dev_info.flags & UBLK_F_ZONED;
>> +}
>> +
>> +static inline bool ublk_queue_is_zoned(struct ublk_queue *ubq)
>> +{
>> +	return ubq->flags & UBLK_F_ZONED;
>> +}
>> +
>> +#ifdef CONFIG_BLK_DEV_ZONED
>> +
>> +static int ublk_get_nr_zones(const struct ublk_device *ub)
>> +{
>> +	const struct ublk_param_basic *p = &ub->params.basic;
>> +
>> +	/* Zone size is a power of 2 */
>> +	return p->dev_sectors >> ilog2(p->chunk_sectors);
>> +}
>> +
>> +static int ublk_revalidate_disk_zones(struct ublk_device *ub)
>> +{
>> +	return blk_revalidate_disk_zones(ub->ub_disk, NULL);
>> +}
>> +
>> +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))
>> +		return -EINVAL;
>> +
>> +	if (!p->max_zone_append_sectors)
>> +		return -EINVAL;
>> +
>> +	nr_zones = ublk_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);
>> +
>> +	ub->ub_disk->nr_zones = ublk_get_nr_zones(ub);
>> +
>> +	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);
>
> 'bufsize' shouldn't related with queue_max_segments() given we don't
> enable segment limit yet.

Ok 👍

>
>> +
>> +	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;
>> +
>> +	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;
>
> pdu->nr_sectors will be set to ublksrv_io_desc->nr_sectors as part of
> UAPI, I feel it is hard to understand to pass 'remaining_zones * zone_size_sectors',
> probably it is fine to re-define as buffer size or requested
> nr_blk_zone, or other ideas?

This is the only place `pdu->nr_sectors` is assigned. We copy the value
to `iod->nr_sectors` when we process the request. So I think that part
is OK.

However, it should be set to `zones_in_request`, not `remaining_zones`.
Otherwise user space might try to write too much to the buffer and get
confused when the write fails.

>
>> +
>> +		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
>> +
>> +#define ublk_report_zones (NULL)
>> +
>> +static int ublk_dev_param_zoned_validate(const struct ublk_device *ub)
>> +{
>> +	return -EOPNOTSUPP;
>> +}
>> +
>> +static int ublk_dev_param_zoned_apply(struct ublk_device *ub)
>> +{
>> +	return -EOPNOTSUPP;
>> +}
>> +
>> +static int ublk_revalidate_disk_zones(struct ublk_device *ub)
>> +{
>> +	return 0;
>> +}
>> +
>> +#endif
>> +
>>  static inline void __ublk_complete_rq(struct request *req);
>>  static void ublk_complete_rq(struct kref *ref);
>>  
>> @@ -232,7 +434,7 @@ 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 +459,8 @@ 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);
>> +
>> +	return 0;
>>  }
>>  
>>  static void ublk_dev_param_discard_apply(struct ublk_device *ub)
>> @@ -286,6 +490,9 @@ 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 +511,31 @@ static int ublk_validate_params(const struct ublk_device *ub)
>>  	if (ub->params.types & UBLK_PARAM_TYPE_DEVT)
>>  		return -EINVAL;
>>  
>> +	if (ub->params.types & UBLK_PARAM_TYPE_ZONED)
>> +		return ublk_dev_param_zoned_validate(ub);
>> +	else if (ublk_dev_is_zoned(ub))
>> +		return -EINVAL;
>> +
>>  	return 0;
>>  }
>>  
>>  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 (ub->params.types & UBLK_PARAM_TYPE_ZONED)
>> +		return ublk_dev_param_zoned_apply(ub);
>> +
>>  	return 0;
>>  }
>>  
>> @@ -487,6 +706,7 @@ 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 +821,8 @@ 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,
>> @@ -685,8 +906,14 @@ 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);
>> +	enum req_op op = req_op(req);
>>  	u32 ublk_op;
>>  
>> +	if (!ublk_queue_is_zoned(ubq) &&
>> +	    (op_is_zone_mgmt(op) || op == REQ_OP_ZONE_APPEND))
>> +		return -EIO;
>> +
>>  	switch (req_op(req)) {
>>  	case REQ_OP_READ:
>>  		ublk_op = UBLK_IO_OP_READ;
>> @@ -703,6 +930,37 @@ 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:
>> +	case REQ_OP_DRV_OUT:
>> +		/* We do not support reset_all and drv_out */
>> +		return BLK_STS_NOTSUPP;
>
> I'd suggest to move all zoned handling & the above check into one helper,
> such as:
>
> 	default:
> 		if (ublk_queue_is_zoned())
> 			return ublk_zoned_setup_iod();
>
> Then zoned check can be avoided for other generic OPs, and zoned patch
> conflict could be avoided usually.

Alright 👍

Best regards,
Andreas

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