On Mon, Apr 14, 2025 at 4:45 AM Jared Holzman <jholzman@xxxxxxxxxx> 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@xxxxxxxxxx>
> ---
> drivers/block/ublk_drv.c | 19 ++++++++++++++++++-
> include/uapi/linux/ublk_cmd.h | 7 +++++++
> 2 files changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index 2fd05c1bd30b..2a8d8b864ef9 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 +3053,17 @@ static int ublk_ctrl_get_features(struct
> io_uring_cmd *cmd)
> return 0;
> }
>
> +static void 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);
Can you pass header instead of cmd to this function? See my recent
commit changing most of the other ublk_ctrl handlers:
https://git.kernel.dk/cgit/linux/commit/?h=block-6.15&id=843c6cec1af85f05971b7baf3704801895e77d76
> + struct ublk_param_basic *p = &ub->params.basic;
> + size_t new_size = (int)header->data[0];
Why cast from u64 to int and back to size_t?
> +
> + mutex_lock(&ub->mutex);
> + p->dev_sectors = new_size;
> + set_capacity_and_notify(ub->ub_disk, p->dev_sectors);
> + mutex_unlock(&ub->mutex);
> +}
> /*
> * All control commands are sent via /dev/ublk-control, so we have to
> check
> * the destination device's permission
> @@ -3137,6 +3149,7 @@ 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 +3241,10 @@ 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):
> + ublk_ctrl_set_size(ub, cmd);
> + ret = 0;
> + 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
"Resisizing" -> "Resizing"?
Best,
Caleb
> + */
> +#define UBLK_F_UPDATE_SIZE (1ULL << 10)
> +
> /* device state */
> #define UBLK_S_DEV_DEAD 0
> #define UBLK_S_DEV_LIVE 1
> --
> 2.43.0
>
>
