[PATCH v6] ublk: Add UBLK_U_CMD_UPDATE_SIZE

[PATCH v6] ublk: Add UBLK_U_CMD_UPDATE_SIZE

[Jared Holzman]

From: Omri Mann <omri@nvidia.com>

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.

Signed-off-by: Omri Mann <omri@nvidia.com>
---
 drivers/block/ublk_drv.c      | 19 ++++++++++++++++++-
 include/uapi/linux/ublk_cmd.h |  8 ++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 2de7b2bd409d..03653bd7a1df 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -50,6 +50,7 @@
 
 /* private ioctl command mirror */
 #define UBLK_CMD_DEL_DEV_ASYNC	_IOC_NR(UBLK_U_CMD_DEL_DEV_ASYNC)
+#define UBLK_CMD_UPDATE_SIZE	_IOC_NR(UBLK_U_CMD_UPDATE_SIZE)
 
 #define UBLK_IO_REGISTER_IO_BUF		_IOC_NR(UBLK_U_IO_REGISTER_IO_BUF)
 #define UBLK_IO_UNREGISTER_IO_BUF	_IOC_NR(UBLK_U_IO_UNREGISTER_IO_BUF)
@@ -64,7 +65,8 @@
 		| 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 \
@@ -3075,6 +3077,16 @@ 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
@@ -3160,6 +3172,7 @@ 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 UBLK_CMD_UPDATE_SIZE:
 		mask = MAY_READ | MAY_WRITE;
 		break;
 	default:
@@ -3251,6 +3264,10 @@ 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 UBLK_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..be5c6c6b16e0 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 +213,12 @@
  */
 #define UBLK_F_USER_RECOVERY_FAIL_IO (1ULL << 9)
 
+/*
+ * Resizing a block device is possible with UBLK_U_CMD_UPDATE_SIZE
+ * New size is passed in cmd->data[0] and is in units of sectors
+ */
+#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 v6] ublk: Add UBLK_U_CMD_UPDATE_SIZE

[Ming Lei]

On Mon, Apr 21, 2025 at 01:59:50PM +0300, Jared Holzman wrote:
> 
> From: Omri Mann <omri@nvidia.com>
> 
> 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.
> 
> Signed-off-by: Omri Mann <omri@nvidia.com>

Looks good,

Reviewed-by: Ming Lei <ming.lei@redhat.com>


Thanks,
Ming

Re: [PATCH v6] ublk: Add UBLK_U_CMD_UPDATE_SIZE

[Jared Holzman]

On 21/04/2025 15:15, Ming Lei wrote:
> On Mon, Apr 21, 2025 at 01:59:50PM +0300, Jared Holzman wrote:
>>
>> From: Omri Mann <omri@nvidia.com>
>>
>> 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.
>>
>> Signed-off-by: Omri Mann <omri@nvidia.com>
> 
> Looks good,
> 
> Reviewed-by: Ming Lei <ming.lei@redhat.com>
> 
> 
> Thanks,
> Ming
> 

Great. Anything more to do from my side? Can I expect to see it in 6.16?

Thanks,

Jared

Re: [PATCH v6] ublk: Add UBLK_U_CMD_UPDATE_SIZE

[Jens Axboe]

On Mon, 21 Apr 2025 13:59:50 +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.
> 
> [...]

Applied, thanks!

[1/1] ublk: Add UBLK_U_CMD_UPDATE_SIZE
      commit: 98b995660bff011d8e00af03abd74ac7d1ac1390

Best regards,
-- 
Jens Axboe