[PATCH v2] ublk: Add UBLK_U_CMD_UPDATE_SIZE

[PATCH v2] ublk: Add UBLK_U_CMD_UPDATE_SIZE

[Jared Holzman]

Currently ublk only allows the size of the ublkb block device to be
set via UBLK_CMD_SET_PARAMS before UBLK_CMD_START_DEV is triggered.

This does not provide support for extendable user-space block devices
without having to stop and restart the underlying ublkb block device
causing IO interruption.

This patch adds a new ublk command UBLK_U_CMD_UPDATE_SIZE to allow the
ublk block device to be resized on-the-fly.

Feature flag UBLK_F_UPDATE_SIZE is also added to indicate support for 
this command.

Signed-off-by: Omri Mann <omri@nvidia.com>
---
  drivers/block/ublk_drv.c      | 23 ++++++++++++++++++++++-
  include/uapi/linux/ublk_cmd.h |  7 +++++++
  2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 2fd05c1bd30b..acf8aa6c4452 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -64,7 +64,8 @@
                 | UBLK_F_CMD_IOCTL_ENCODE \
                 | UBLK_F_USER_COPY \
                 | UBLK_F_ZONED \
-               | UBLK_F_USER_RECOVERY_FAIL_IO)
+               | UBLK_F_USER_RECOVERY_FAIL_IO \
+               | UBLK_F_UPDATE_SIZE)

  #define UBLK_F_ALL_RECOVERY_FLAGS (UBLK_F_USER_RECOVERY \
                 | UBLK_F_USER_RECOVERY_REISSUE \
@@ -3052,6 +3053,22 @@ static int ublk_ctrl_get_features(struct 
io_uring_cmd *cmd)
         return 0;
  }

+static int ublk_ctrl_set_size(struct ublk_device *ub,
+               struct io_uring_cmd *cmd)
+{
+       const struct ublksrv_ctrl_cmd *header = io_uring_sqe_cmd(cmd->sqe);
+       struct ublk_param_basic *p = &ub->params.basic;
+       size_t new_size = (int)header->data[0];
+       int ret = 0;
+
+       p->dev_sectors = new_size;
+
+       mutex_lock(&ub->mutex);
+       set_capacity_and_notify(ub->ub_disk, p->dev_sectors);
+       mutex_unlock(&ub->mutex);
+
+       return ret;
+}

  /*
   * All control commands are sent via /dev/ublk-control, so we have to 
check
   * the destination device's permission
@@ -3137,6 +3154,7 @@ static int ublk_ctrl_uring_cmd_permission(struct 
ublk_device *ub,
         case UBLK_CMD_SET_PARAMS:
         case UBLK_CMD_START_USER_RECOVERY:
         case UBLK_CMD_END_USER_RECOVERY:
+       case _IOC_NR(UBLK_U_CMD_UPDATE_SIZE):
                 mask = MAY_READ | MAY_WRITE;
                 break;
         default:
@@ -3228,6 +3246,9 @@ static int ublk_ctrl_uring_cmd(struct io_uring_cmd 
*cmd,
         case UBLK_CMD_END_USER_RECOVERY:
                 ret = ublk_ctrl_end_recovery(ub, cmd);
                 break;
+       case _IOC_NR(UBLK_U_CMD_UPDATE_SIZE):
+               ret = ublk_ctrl_set_size(ub, cmd);
+               break;
         default:
                 ret = -EOPNOTSUPP;
                 break;
diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
index 583b86681c93..0e40e497c28f 100644
--- a/include/uapi/linux/ublk_cmd.h
+++ b/include/uapi/linux/ublk_cmd.h
@@ -51,6 +51,8 @@
         _IOR('u', 0x13, struct ublksrv_ctrl_cmd)
  #define UBLK_U_CMD_DEL_DEV_ASYNC       \
         _IOR('u', 0x14, struct ublksrv_ctrl_cmd)
+#define UBLK_U_CMD_UPDATE_SIZE         \
+       _IOWR('u', 0x15, struct ublksrv_ctrl_cmd)

  /*
   * 64bits are enough now, and it should be easy to extend in case of
@@ -211,6 +213,11 @@
   */
  #define UBLK_F_USER_RECOVERY_FAIL_IO (1ULL << 9)

+/*
+ * Resisizing a block device is possible with UBLK_U_CMD_UPDATE_SIZE
+ */
+#define UBLK_F_UPDATE_SIZE              (1ULL << 10)
+
  /* device state */
  #define UBLK_S_DEV_DEAD        0
  #define UBLK_S_DEV_LIVE        1
-- 
2.43.0

Re: [PATCH v2] ublk: Add UBLK_U_CMD_UPDATE_SIZE

[Jens Axboe]

On 4/10/25 6:29 AM, Jared Holzman wrote:
> @@ -3052,6 +3053,22 @@ static int ublk_ctrl_get_features(struct io_uring_cmd *cmd)
>         return 0;
>  }
> 
> +static int ublk_ctrl_set_size(struct ublk_device *ub,
> +               struct io_uring_cmd *cmd)

Minor style nit, but that would fit on a single line, doesn't need to be
split in two.

> +{
> +       const struct ublksrv_ctrl_cmd *header = io_uring_sqe_cmd(cmd->sqe);
> +       struct ublk_param_basic *p = &ub->params.basic;
> +       size_t new_size = (int)header->data[0];
> +       int ret = 0;
> +
> +       p->dev_sectors = new_size;
> +
> +       mutex_lock(&ub->mutex);
> +       set_capacity_and_notify(ub->ub_disk, p->dev_sectors);
> +       mutex_unlock(&ub->mutex);
> +
> +       return ret;
> +}

Get rid of 'ret' here, it's entirely unused. In fact maybe just get rid
of the return value in the first place, as the function can't fail?

-- 
Jens Axboe

Re: [PATCH v2] ublk: Add UBLK_U_CMD_UPDATE_SIZE

[Ming Lei]

On Thu, Apr 10, 2025 at 03:29:38PM +0300, Jared Holzman wrote:
> Currently ublk only allows the size of the ublkb block device to be
> set via UBLK_CMD_SET_PARAMS before UBLK_CMD_START_DEV is triggered.
> 
> This does not provide support for extendable user-space block devices
> without having to stop and restart the underlying ublkb block device
> causing IO interruption.
> 
> This patch adds a new ublk command UBLK_U_CMD_UPDATE_SIZE to allow the
> ublk block device to be resized on-the-fly.
> 
> Feature flag UBLK_F_UPDATE_SIZE is also added to indicate support for this
> command.
> 
> Signed-off-by: Omri Mann <omri@nvidia.com>
> ---
>  drivers/block/ublk_drv.c      | 23 ++++++++++++++++++++++-
>  include/uapi/linux/ublk_cmd.h |  7 +++++++
>  2 files changed, 29 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index 2fd05c1bd30b..acf8aa6c4452 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -64,7 +64,8 @@
>                 | UBLK_F_CMD_IOCTL_ENCODE \
>                 | UBLK_F_USER_COPY \
>                 | UBLK_F_ZONED \
> -               | UBLK_F_USER_RECOVERY_FAIL_IO)
> +               | UBLK_F_USER_RECOVERY_FAIL_IO \
> +               | UBLK_F_UPDATE_SIZE)
> 
>  #define UBLK_F_ALL_RECOVERY_FLAGS (UBLK_F_USER_RECOVERY \
>                 | UBLK_F_USER_RECOVERY_REISSUE \
> @@ -3052,6 +3053,22 @@ static int ublk_ctrl_get_features(struct io_uring_cmd
> *cmd)
>         return 0;
>  }
> 
> +static int ublk_ctrl_set_size(struct ublk_device *ub,
> +               struct io_uring_cmd *cmd)
> +{
> +       const struct ublksrv_ctrl_cmd *header = io_uring_sqe_cmd(cmd->sqe);
> +       struct ublk_param_basic *p = &ub->params.basic;
> +       size_t new_size = (int)header->data[0];
> +       int ret = 0;
> +
> +       p->dev_sectors = new_size;

The above line need to be protected by ub->mutex.


thanks,
Ming