[PATCH 0/2 blktests] Update the miniublk to use ioctl opcodes

[PATCH 0/2 blktests] Update the miniublk to use ioctl opcodes

[Sebastian Chlad]

miniublk currently uses only legacy opcodes. Kernels built without
CONFIG_BLKDEV_UBLK_LEGACY_OPCODES reject them with -EOPNOTSUPP, causing
all ublk tests to fail. This patch solves the problem and the following
patch adds fallback to legacy opcodes for testing of the older kernels.

I tested against the old 6.3 kernel supporting only legacy opcodes. Also
against new kernel with ioctl opcodes and legacy opcodes still enabled as
well as the new kernel with ioctl opcodes and no support for the legacy ones.

Sebastian Chlad (2):
  src/miniublk: switch to ioctl-encoded ublk commands
  src/miniublk: fall back to legacy opcodes on older kernels

 src/miniublk.c | 77 +++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 57 insertions(+), 20 deletions(-)

-- 
2.51.0

[PATCH 1/2 blktests] src/miniublk: switch to ioctl-encoded ublk commands

[Sebastian Chlad]

Kernels built without CONFIG_BLKDEV_UBLK_LEGACY_OPCODES reject the
legacy raw UBLK_CMD_* and UBLK_IO_* opcodes. Switch miniublk to use
the ioctl-encoded UBLK_U_CMD_* and UBLK_U_IO_* variants defined in
linux/ublk_cmd.h instead.

For IO commands, the ioctl-encoded opcode is used for submission while
_IOC_NR() extracts the raw NR bits for build_user_data(), keeping the
user_data tag encoding intact.

Signed-off-by: Sebastian Chlad <sebastian.chlad@suse.com>
---
 src/miniublk.c | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/src/miniublk.c b/src/miniublk.c
index f98f850..5a35ca7 100644
--- a/src/miniublk.c
+++ b/src/miniublk.c
@@ -294,7 +294,7 @@ static int __ublk_ctrl_cmd(struct ublk_dev *dev,
 int ublk_ctrl_stop_dev(struct ublk_dev *dev)
 {
 	struct ublk_ctrl_cmd_data data = {
-		.cmd_op	= UBLK_CMD_STOP_DEV,
+		.cmd_op	= UBLK_U_CMD_STOP_DEV,
 	};
 
 	return __ublk_ctrl_cmd(dev, &data);
@@ -304,7 +304,7 @@ int ublk_ctrl_start_dev(struct ublk_dev *dev,
 		int daemon_pid)
 {
 	struct ublk_ctrl_cmd_data data = {
-		.cmd_op	= UBLK_CMD_START_DEV,
+		.cmd_op	= UBLK_U_CMD_START_DEV,
 		.flags	= CTRL_CMD_HAS_DATA,
 	};
 
@@ -316,7 +316,7 @@ int ublk_ctrl_start_dev(struct ublk_dev *dev,
 int ublk_ctrl_add_dev(struct ublk_dev *dev)
 {
 	struct ublk_ctrl_cmd_data data = {
-		.cmd_op	= UBLK_CMD_ADD_DEV,
+		.cmd_op	= UBLK_U_CMD_ADD_DEV,
 		.flags	= CTRL_CMD_HAS_BUF,
 		.addr = (__u64)&dev->dev_info,
 		.len = sizeof(struct ublksrv_ctrl_dev_info),
@@ -328,7 +328,7 @@ int ublk_ctrl_add_dev(struct ublk_dev *dev)
 int ublk_ctrl_del_dev(struct ublk_dev *dev)
 {
 	struct ublk_ctrl_cmd_data data = {
-		.cmd_op = UBLK_CMD_DEL_DEV,
+		.cmd_op = UBLK_U_CMD_DEL_DEV,
 		.flags = 0,
 	};
 
@@ -338,7 +338,7 @@ int ublk_ctrl_del_dev(struct ublk_dev *dev)
 int ublk_ctrl_get_info(struct ublk_dev *dev)
 {
 	struct ublk_ctrl_cmd_data data = {
-		.cmd_op	= UBLK_CMD_GET_DEV_INFO,
+		.cmd_op	= UBLK_U_CMD_GET_DEV_INFO,
 		.flags	= CTRL_CMD_HAS_BUF,
 		.addr = (__u64)&dev->dev_info,
 		.len = sizeof(struct ublksrv_ctrl_dev_info),
@@ -351,7 +351,7 @@ int ublk_ctrl_set_params(struct ublk_dev *dev,
 		struct ublk_params *params)
 {
 	struct ublk_ctrl_cmd_data data = {
-		.cmd_op	= UBLK_CMD_SET_PARAMS,
+		.cmd_op	= UBLK_U_CMD_SET_PARAMS,
 		.flags	= CTRL_CMD_HAS_BUF,
 		.addr = (__u64)params,
 		.len = sizeof(*params),
@@ -364,7 +364,7 @@ static int ublk_ctrl_get_params(struct ublk_dev *dev,
 		struct ublk_params *params)
 {
 	struct ublk_ctrl_cmd_data data = {
-		.cmd_op	= UBLK_CMD_GET_PARAMS,
+		.cmd_op	= UBLK_U_CMD_GET_PARAMS,
 		.flags	= CTRL_CMD_HAS_BUF,
 		.addr = (__u64)params,
 		.len = sizeof(*params),
@@ -378,7 +378,7 @@ static int ublk_ctrl_get_params(struct ublk_dev *dev,
 static int ublk_ctrl_start_user_recover(struct ublk_dev *dev)
 {
 	struct ublk_ctrl_cmd_data data = {
-		.cmd_op	= UBLK_CMD_START_USER_RECOVERY,
+		.cmd_op	= UBLK_U_CMD_START_USER_RECOVERY,
 		.flags	= 0,
 	};
 
@@ -389,7 +389,7 @@ static int ublk_ctrl_end_user_recover(struct ublk_dev *dev,
 		int daemon_pid)
 {
 	struct ublk_ctrl_cmd_data data = {
-		.cmd_op	= UBLK_CMD_END_USER_RECOVERY,
+		.cmd_op	= UBLK_U_CMD_END_USER_RECOVERY,
 		.flags	= CTRL_CMD_HAS_DATA,
 	};
 
@@ -624,9 +624,9 @@ static int ublk_queue_io_cmd(struct ublk_queue *q,
 		return 0;
 
 	if (io->flags & UBLKSRV_NEED_COMMIT_RQ_COMP)
-		cmd_op = UBLK_IO_COMMIT_AND_FETCH_REQ;
-	else if (io->flags & UBLKSRV_NEED_FETCH_RQ)
-		cmd_op = UBLK_IO_FETCH_REQ;
+		cmd_op = UBLK_U_IO_COMMIT_AND_FETCH_REQ;
+	else
+		cmd_op = UBLK_U_IO_FETCH_REQ;
 
 	sqe = io_uring_get_sqe(&q->ring);
 	if (!sqe) {
@@ -637,7 +637,7 @@ static int ublk_queue_io_cmd(struct ublk_queue *q,
 
 	cmd = (struct ublksrv_io_cmd *)ublk_get_sqe_cmd(sqe);
 
-	if (cmd_op == UBLK_IO_COMMIT_AND_FETCH_REQ)
+	if (io->flags & UBLKSRV_NEED_COMMIT_RQ_COMP)
 		cmd->result = io->result;
 
 	/* These fields should be written once, never change */
@@ -650,7 +650,7 @@ static int ublk_queue_io_cmd(struct ublk_queue *q,
 	cmd->addr	= (__u64)io->buf_addr;
 	cmd->q_id	= q->q_id;
 
-	user_data = build_user_data(tag, cmd_op, 0, 0);
+	user_data = build_user_data(tag, _IOC_NR(cmd_op), 0, 0);
 	io_uring_sqe_set_data64(sqe, user_data);
 
 	io->flags = 0;
@@ -658,7 +658,7 @@ static int ublk_queue_io_cmd(struct ublk_queue *q,
 	q->cmd_inflight += 1;
 
 	ublk_dbg(UBLK_DBG_IO_CMD, "%s: (qid %d tag %u cmd_op %u) iof %x stopping %d\n",
-			__func__, q->q_id, tag, cmd_op,
+			__func__, q->q_id, tag, _IOC_NR(cmd_op),
 			io->flags, !!(q->state & UBLKSRV_QUEUE_STOPPING));
 	return 1;
 }
-- 
2.51.0

[PATCH 2/2 blktests] src/miniublk: fall back to legacy opcodes on older kernels

[Sebastian Chlad]

Try ioctl-encoded ADD_DEV and GET_DEV_INFO first; if either fails,
retry with the legacy raw opcode. After a successful bootstrap
command, derive use_ioctl from UBLK_F_CMD_IOCTL_ENCODE in dev_info.flags
so all subsequent control and IO commands use the mode reported by the
kernel.

Signed-off-by: Sebastian Chlad <sebastian.chlad@suse.com>
---
 src/miniublk.c | 47 ++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 42 insertions(+), 5 deletions(-)

diff --git a/src/miniublk.c b/src/miniublk.c
index 5a35ca7..494a4ae 100644
--- a/src/miniublk.c
+++ b/src/miniublk.c
@@ -112,6 +112,7 @@ struct ublk_dev {
 	int fds[2];	/* fds[0] points to /dev/ublkcN */
 	int nr_fds;
 	int ctrl_fd;
+	bool use_ioctl;
 	struct io_uring ring;
 };
 
@@ -235,7 +236,7 @@ static inline int ublk_setup_ring(struct io_uring *r, int depth,
 
 static inline void ublk_ctrl_init_cmd(struct ublk_dev *dev,
 		struct io_uring_sqe *sqe,
-		struct ublk_ctrl_cmd_data *data)
+		struct ublk_ctrl_cmd_data *data, __u32 cmd_op)
 {
 	struct ublksrv_ctrl_dev_info *info = &dev->dev_info;
 	struct ublksrv_ctrl_cmd *cmd = (struct ublksrv_ctrl_cmd *)ublk_get_sqe_cmd(sqe);
@@ -255,25 +256,34 @@ static inline void ublk_ctrl_init_cmd(struct ublk_dev *dev,
 	cmd->dev_id = info->dev_id;
 	cmd->queue_id = -1;
 
-	ublk_set_sqe_cmd_op(sqe, data->cmd_op);
+	ublk_set_sqe_cmd_op(sqe, cmd_op);
 
 	io_uring_sqe_set_data(sqe, cmd);
 }
 
+static void ublk_update_ioctl_encoding(struct ublk_dev *dev)
+{
+	dev->use_ioctl = !!(dev->dev_info.flags & UBLK_F_CMD_IOCTL_ENCODE);
+}
+
 static int __ublk_ctrl_cmd(struct ublk_dev *dev,
 		struct ublk_ctrl_cmd_data *data)
 {
 	struct io_uring_sqe *sqe;
 	struct io_uring_cqe *cqe;
+	__u32 cmd_op = data->cmd_op;
 	int ret = -EINVAL;
 
+	if (!dev->use_ioctl)
+		cmd_op = _IOC_NR(cmd_op);
+
 	sqe = io_uring_get_sqe(&dev->ring);
 	if (!sqe) {
 		ublk_err("%s: can't get sqe ret %d\n", __func__, ret);
 		return ret;
 	}
 
-	ublk_ctrl_init_cmd(dev, sqe, data);
+	ublk_ctrl_init_cmd(dev, sqe, data, cmd_op);
 
 	ret = io_uring_submit(&dev->ring);
 	if (ret < 0) {
@@ -321,8 +331,19 @@ int ublk_ctrl_add_dev(struct ublk_dev *dev)
 		.addr = (__u64)&dev->dev_info,
 		.len = sizeof(struct ublksrv_ctrl_dev_info),
 	};
+	int ret;
 
-	return __ublk_ctrl_cmd(dev, &data);
+	ret = __ublk_ctrl_cmd(dev, &data);
+	if (ret < 0) {
+		/* retry with legacy opcode on older kernels */
+		dev->use_ioctl = false;
+		ret = __ublk_ctrl_cmd(dev, &data);
+	}
+
+	if (ret >= 0)
+		ublk_update_ioctl_encoding(dev);
+
+	return ret;
 }
 
 int ublk_ctrl_del_dev(struct ublk_dev *dev)
@@ -343,8 +364,19 @@ int ublk_ctrl_get_info(struct ublk_dev *dev)
 		.addr = (__u64)&dev->dev_info,
 		.len = sizeof(struct ublksrv_ctrl_dev_info),
 	};
+	int ret;
 
-	return __ublk_ctrl_cmd(dev, &data);
+	ret = __ublk_ctrl_cmd(dev, &data);
+	if (ret < 0 && dev->use_ioctl) {
+		/* retry with legacy opcode on older kernels */
+		dev->use_ioctl = false;
+		ret = __ublk_ctrl_cmd(dev, &data);
+	}
+
+	if (ret >= 0)
+		ublk_update_ioctl_encoding(dev);
+
+	return ret;
 }
 
 int ublk_ctrl_set_params(struct ublk_dev *dev,
@@ -453,6 +485,8 @@ static struct ublk_dev *ublk_ctrl_init()
 	struct ublksrv_ctrl_dev_info *info = &dev->dev_info;
 	int ret;
 
+	dev->use_ioctl = true; /* use ioctl opcodes by default */
+
 	dev->ctrl_fd = open(CTRL_DEV, O_RDWR);
 	if (dev->ctrl_fd < 0) {
 		ublk_err("control dev %s can't be opened: %m %d\n", CTRL_DEV, errno);
@@ -628,6 +662,9 @@ static int ublk_queue_io_cmd(struct ublk_queue *q,
 	else
 		cmd_op = UBLK_U_IO_FETCH_REQ;
 
+	if (!q->dev->use_ioctl)
+		cmd_op = _IOC_NR(cmd_op);
+
 	sqe = io_uring_get_sqe(&q->ring);
 	if (!sqe) {
 		ublk_err("%s: run out of sqe %d, tag %d\n",
-- 
2.51.0

Re: [PATCH 1/2 blktests] src/miniublk: switch to ioctl-encoded ublk commands

[Shin'ichiro Kawasaki]

Hi Sebastian,

Thanks for the patches. I agree that this direction is good: it's the better
shift away from the legacy interface.

One point I noticed is that src/miniublk.c can no longer be built with the
kernel headers of the LTS kernel version v6.1.y, probably (v5.15.y does not have
ublk and v6.6.y supports the new interface). This is a rather small window, and
may be acceptable but I wonder what you think about it

If we drop the miniublk build with v6.1.y kernel headers, it might be the better
to check before building miniublk. I quickly created a Makefile change [1] for
that purpose.

Also, please find a comment in line below.

On Jun 17, 2026 / 09:25, Sebastian Chlad wrote:
> Kernels built without CONFIG_BLKDEV_UBLK_LEGACY_OPCODES reject the
> legacy raw UBLK_CMD_* and UBLK_IO_* opcodes. Switch miniublk to use
> the ioctl-encoded UBLK_U_CMD_* and UBLK_U_IO_* variants defined in
> linux/ublk_cmd.h instead.
> 
> For IO commands, the ioctl-encoded opcode is used for submission while
> _IOC_NR() extracts the raw NR bits for build_user_data(), keeping the
> user_data tag encoding intact.
> 
> Signed-off-by: Sebastian Chlad <sebastian.chlad@suse.com>
> ---
>  src/miniublk.c | 30 +++++++++++++++---------------
>  1 file changed, 15 insertions(+), 15 deletions(-)
> 
> diff --git a/src/miniublk.c b/src/miniublk.c
> index f98f850..5a35ca7 100644
> --- a/src/miniublk.c
> +++ b/src/miniublk.c
[...]
> @@ -624,9 +624,9 @@ static int ublk_queue_io_cmd(struct ublk_queue *q,
>  		return 0;
>  
>  	if (io->flags & UBLKSRV_NEED_COMMIT_RQ_COMP)
> -		cmd_op = UBLK_IO_COMMIT_AND_FETCH_REQ;
> -	else if (io->flags & UBLKSRV_NEED_FETCH_RQ)
> -		cmd_op = UBLK_IO_FETCH_REQ;
> +		cmd_op = UBLK_U_IO_COMMIT_AND_FETCH_REQ;
> +	else
> +		cmd_op = UBLK_U_IO_FETCH_REQ;

The hunk above changes the "else if" part, is this intentional?


[1]

diff --git a/src/Makefile b/src/Makefile
index d8833bf..adfe3ef 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -8,6 +8,10 @@ HAVE_C_MACRO = $(shell if echo "$(H)include <$(1)>" |	\
 		$(CC) $(CFLAGS) -E - 2>&1 /dev/null | grep $(2) > /dev/null 2>&1; \
 		then echo 1;else echo 0; fi)
 
+HAVE_C_DEF = $(shell if echo -e "$(H)include <$(1)>\n#ifdef $(2)\nHAVE_$(2)\n#endif" | \
+		$(CC) $(CFLAGS) -E - 2>&1 /dev/null | grep HAVE_$(2) > /dev/null 2>&1; \
+		then echo 1;else echo 0; fi)
+
 C_TARGETS := \
 	dio-offsets \
 	loblksize \
@@ -27,6 +31,7 @@ C_UBLK_TARGETS := miniublk
 
 HAVE_LIBURING := $(call HAVE_C_MACRO,liburing.h,IORING_OP_URING_CMD)
 HAVE_UBLK_HEADER := $(call HAVE_C_HEADER,linux/ublk_cmd.h,1)
+HAVE_NEW_UBLK_INTF := $(call HAVE_C_DEF,linux/ublk_cmd.h,UBLK_U_CMD_START_DEV)
 
 CXX_TARGETS := \
 	discontiguous-io
@@ -37,8 +42,12 @@ SYZKALLER_TARGETS := \
 TARGETS := $(C_TARGETS) $(CXX_TARGETS) $(SYZKALLER_TARGETS)
 
 ifeq ($(HAVE_UBLK_HEADER), 1)
+ifeq ($(HAVE_NEW_UBLK_INTF), 1)
 C_URING_TARGETS += $(C_UBLK_TARGETS)
 else
+$(info Skip $(C_UBLK_TARGETS) build due to missing new ublk interface(v6.4+))
+endif
+else
 $(info Skip $(C_UBLK_TARGETS) build due to missing kernel header(v6.0+))
 endif