Re: [PATCH v2] block: ublk: enable zoned storage support

[Andreas Hindborg <nmi@metaspace.dk>]

Hans Holmberg <hans@owltronix.com> writes:

> On Fri, Feb 24, 2023 at 9:06 PM Andreas Hindborg <nmi@metaspace.dk> 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
>
> Reset all is missing, right? Might as well define that before there are
> users of the ublk<->ublksrv interface.

REQ_OP_ZONE_APPEND and REQ_OP_ZONE_RESET_ALL are not handled in this
patch. REQ_OP_* are converted to UBLK_IO_OP_* in ublk_setup_iod() in an
extensible way. It should be no problem adding support for more
operations later without breaking backwards compatibility.

>
>>
>> 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@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++) {
>> +               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;
>> +
>> +               ret = blk_rq_map_kern(disk->queue, req, &info, sizeof(info),
>> +                                     GFP_KERNEL);
>> +
>> +               if (ret)
>> +                       goto out;
>> +
>> +               status = blk_execute_rq(req, 0);
>
> Pingponging with userspace to retrieve thousand(s) of zone states is
> very inefficient, so I don't think we
> want to define the report zone ublk uapi to be one-zone-per-call.

I agree. I chose this implementation because it was not clear to me how
to communicate the zone report request details to user space. But I
think we can overload the nr_sectors and start_sector of the iod to
communicate the size of the report request.

> Also, just overloading REQ_OP_DRV_IN with report zones instead of
> defining a zone-report specific call does
> not seem future proof - there might be a need to do other
> driver-specific calls in the future.

Yea, ublk does not currently have a command field in the request pdu, so
I did not want to add that. However, it makes sense if we ever want to
use REQ_OP_DRV_IN for anything other than zone report.

>
> Virtio blk implements reporting in a better way - se
> virtblk_report_zones (that just got merged in Linus tree)
> The same type of interface should be possible for ublk.

Something like that could work 👍

>> +               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;
>> +}
>> +#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 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
>>         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;
>> +};
>> +
>>  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
>>
>> base-commit: c9c3395d5e3dcc6daee66c6908354d47bf98cb0c
>> --
>> 2.39.2
>>