On 17/04/2025 21:23, Uday Shankar wrote:
On Wed, Apr 16, 2025 at 01:07:47PM +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.
Many of the other parameters in ublk_params/ublksrv_ctrl_dev_info could
also feasibly be changed after initial device creation/start. Is it
possible to design the API in a way so that we don't have to have one
command per parameter?
Already spoke to Ming about this. Changing the size is reasonable and
easy with a simple api call i.e. set_capacity_and_notify()
Changing the other parameters I struggle to see a reasonable need for it
and is significantly more complicated.
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 | 18 +++++++++++++++++-
include/uapi/linux/ublk_cmd.h | 7 +++++++
2 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index cdb1543fa4a9..128f094efbad 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 \
@@ -3067,6 +3068,16 @@ static int ublk_ctrl_get_features(const struct
ublksrv_ctrl_cmd *header)
return 0;
}
+static void ublk_ctrl_set_size(struct ublk_device *ub, const struct
ublksrv_ctrl_cmd *header)
+{
+ struct ublk_param_basic *p = &ub->params.basic;
+ u64 new_size = header->data[0];
+
+ 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
@@ -3152,6 +3163,7 @@ 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:
@@ -3243,6 +3255,10 @@ static int ublk_ctrl_uring_cmd(struct io_uring_cmd
*cmd,
case UBLK_CMD_END_USER_RECOVERY:
ret = ublk_ctrl_end_recovery(ub, header);
break;
+ case _IOC_NR(UBLK_U_CMD_UPDATE_SIZE):
+ ublk_ctrl_set_size(ub, header);
+ 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..587a54b3cfe1 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)
+/*
+ * Resizing 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
--
Jared Holzman
Senior Software Engineer
NVIDIA
jholzman@xxxxxxxxxx
