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    SubjectRe: [PATCH v2] block: ublk: enable zoned storage support
    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.

    >
    > 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.

    > + 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?

    > +
    > + 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().

    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?

    > + 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.

    > };
    >
    > #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.

    > 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?

    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.


    Thanks,
    Ming

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