From: Omri Mann <omri@nvidia.com>
Date: Mon, 21 Apr 2025 10:59:50 +0000 (+0300)
Subject: ublk: Add UBLK_U_CMD_UPDATE_SIZE
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=98b995660bff011d8e00af03abd74ac7d1ac1390;p=nvme.git

ublk: Add UBLK_U_CMD_UPDATE_SIZE

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>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/2a370ab1-d85b-409d-b762-f9f3f6bdf705@nvidia.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

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