[PATCH v3 0/4] io_uring: Pass the whole sqe to commands

[PATCH v3 0/4] io_uring: Pass the whole sqe to commands

[Breno Leitao]

These three patches prepare for the sock support in the io_uring cmd, as
described in the following RFC:

	https://lore.kernel.org/lkml/20230406144330.1932798-1-leitao@debian.org/

Since the support linked above depends on other refactors, such as the sock
ioctl() sock refactor[1], I would like to start integrating patches that have
consensus and can bring value right now.  This will also reduce the patchset
size later.

Regarding to these three patches, they are simple changes that turn
io_uring cmd subsystem more flexible (by passing the whole SQE to the
command), and cleaning up an unnecessary compile check.

These patches were tested by creating a file system and mounting an NVME disk
using ubdsrv/ublkb0.

[1] ZD6Zw1GAZR28++3v@gmail.com/">https://lore.kernel.org/lkml/ZD6Zw1GAZR28++3v@gmail.com/

Reviewed-by: Kanchan Joshi <joshi.k@samsung.com>

V1 -> V2 :
  * Create a helper to return the size of the SQE
V2 -> V3:
  * Transformed uring_sqe_size() into a proper function
  * Fixed some commit messages
  * Created a helper function for nvme/host to avoid casting
  * Added a fourth patch to avoid ublk_drv's casts by using a proper helper

Breno Leitao (4):
  io_uring: Create a helper to return the SQE size
  io_uring: Pass whole sqe to commands
  io_uring: Remove unnecessary BUILD_BUG_ON
  block: ublk_drv: Add a helper instead of casting

 drivers/block/ublk_drv.c  | 36 ++++++++++++++++++++++++------------
 drivers/nvme/host/ioctl.c |  8 +++++++-
 include/linux/io_uring.h  |  2 +-
 io_uring/io_uring.h       | 10 ++++++++++
 io_uring/opdef.c          |  2 +-
 io_uring/uring_cmd.c      | 13 ++++---------
 io_uring/uring_cmd.h      |  8 --------
 7 files changed, 47 insertions(+), 32 deletions(-)

-- 
2.34.1

[PATCH v3 1/4] io_uring: Create a helper to return the SQE size

[Breno Leitao]

Create a simple helper that returns the size of the SQE. The SQE could
have two size, depending of the flags.

If IO_URING_SETUP_SQE128 flag is set, then return a double SQE,
otherwise returns the sizeof of io_uring_sqe (64 bytes).

Signed-off-by: Breno Leitao <leitao@debian.org>
---
 io_uring/io_uring.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index 25515d69d205..259bf798a390 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -394,4 +394,14 @@ static inline void io_req_queue_tw_complete(struct io_kiocb *req, s32 res)
 	io_req_task_work_add(req);
 }
 
+/*
+ * IORING_SETUP_SQE128 contexts allocate twice the normal SQE size for each
+ * slot.
+ */
+static inline size_t uring_sqe_size(struct io_ring_ctx *ctx)
+{
+	if (ctx->flags & IORING_SETUP_SQE128)
+		return 2 * sizeof(struct io_uring_sqe);
+	return sizeof(struct io_uring_sqe);
+}
 #endif
-- 
2.34.1

Re: [PATCH v3 1/4] io_uring: Create a helper to return the SQE size

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

[PATCH v3 2/4] io_uring: Pass whole sqe to commands

[Breno Leitao]

Currently uring CMD operation relies on having large SQEs, but future
operations might want to use normal SQE.

The io_uring_cmd currently only saves the payload (cmd) part of the SQE,
but, for commands that use normal SQE size, it might be necessary to
access the initial SQE fields outside of the payload/cmd block.  So,
saves the whole SQE other than just the pdu.

This changes slightly how the io_uring_cmd works, since the cmd
structures and callbacks are not opaque to io_uring anymore. I.e, the
callbacks can look at the SQE entries, not only, in the cmd structure.

The main advantage is that we don't need to create custom structures for
simple commands.

Suggested-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Keith Busch <kbusch@kernel.org>
---
 drivers/block/ublk_drv.c  | 24 ++++++++++++------------
 drivers/nvme/host/ioctl.c |  8 +++++++-
 include/linux/io_uring.h  |  2 +-
 io_uring/opdef.c          |  2 +-
 io_uring/uring_cmd.c      | 10 ++++------
 5 files changed, 25 insertions(+), 21 deletions(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index c73cc57ec547..ec23a3c9fac8 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -1263,7 +1263,7 @@ static void ublk_handle_need_get_data(struct ublk_device *ub, int q_id,
 
 static int ublk_ch_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
 {
-	struct ublksrv_io_cmd *ub_cmd = (struct ublksrv_io_cmd *)cmd->cmd;
+	struct ublksrv_io_cmd *ub_cmd = (struct ublksrv_io_cmd *)cmd->sqe->cmd;
 	struct ublk_device *ub = cmd->file->private_data;
 	struct ublk_queue *ubq;
 	struct ublk_io *io;
@@ -1567,7 +1567,7 @@ static struct ublk_device *ublk_get_device_from_id(int idx)
 
 static int ublk_ctrl_start_dev(struct ublk_device *ub, struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
+	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
 	int ublksrv_pid = (int)header->data[0];
 	struct gendisk *disk;
 	int ret = -EINVAL;
@@ -1630,7 +1630,7 @@ static int ublk_ctrl_start_dev(struct ublk_device *ub, struct io_uring_cmd *cmd)
 static int ublk_ctrl_get_queue_affinity(struct ublk_device *ub,
 		struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
+	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
 	void __user *argp = (void __user *)(unsigned long)header->addr;
 	cpumask_var_t cpumask;
 	unsigned long queue;
@@ -1681,7 +1681,7 @@ static inline void ublk_dump_dev_info(struct ublksrv_ctrl_dev_info *info)
 
 static int ublk_ctrl_add_dev(struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
+	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
 	void __user *argp = (void __user *)(unsigned long)header->addr;
 	struct ublksrv_ctrl_dev_info info;
 	struct ublk_device *ub;
@@ -1844,7 +1844,7 @@ static int ublk_ctrl_del_dev(struct ublk_device **p_ub)
 
 static inline void ublk_ctrl_cmd_dump(struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
+	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
 
 	pr_devel("%s: cmd_op %x, dev id %d qid %d data %llx buf %llx len %u\n",
 			__func__, cmd->cmd_op, header->dev_id, header->queue_id,
@@ -1863,7 +1863,7 @@ static int ublk_ctrl_stop_dev(struct ublk_device *ub)
 static int ublk_ctrl_get_dev_info(struct ublk_device *ub,
 		struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
+	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
 	void __user *argp = (void __user *)(unsigned long)header->addr;
 
 	if (header->len < sizeof(struct ublksrv_ctrl_dev_info) || !header->addr)
@@ -1894,7 +1894,7 @@ static void ublk_ctrl_fill_params_devt(struct ublk_device *ub)
 static int ublk_ctrl_get_params(struct ublk_device *ub,
 		struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
+	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
 	void __user *argp = (void __user *)(unsigned long)header->addr;
 	struct ublk_params_header ph;
 	int ret;
@@ -1925,7 +1925,7 @@ static int ublk_ctrl_get_params(struct ublk_device *ub,
 static int ublk_ctrl_set_params(struct ublk_device *ub,
 		struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
+	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
 	void __user *argp = (void __user *)(unsigned long)header->addr;
 	struct ublk_params_header ph;
 	int ret = -EFAULT;
@@ -1983,7 +1983,7 @@ static void ublk_queue_reinit(struct ublk_device *ub, struct ublk_queue *ubq)
 static int ublk_ctrl_start_recovery(struct ublk_device *ub,
 		struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
+	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
 	int ret = -EINVAL;
 	int i;
 
@@ -2025,7 +2025,7 @@ static int ublk_ctrl_start_recovery(struct ublk_device *ub,
 static int ublk_ctrl_end_recovery(struct ublk_device *ub,
 		struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
+	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
 	int ublksrv_pid = (int)header->data[0];
 	int ret = -EINVAL;
 
@@ -2092,7 +2092,7 @@ static int ublk_char_dev_permission(struct ublk_device *ub,
 static int ublk_ctrl_uring_cmd_permission(struct ublk_device *ub,
 		struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
+	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
 	bool unprivileged = ub->dev_info.flags & UBLK_F_UNPRIVILEGED_DEV;
 	void __user *argp = (void __user *)(unsigned long)header->addr;
 	char *dev_path = NULL;
@@ -2171,7 +2171,7 @@ static int ublk_ctrl_uring_cmd_permission(struct ublk_device *ub,
 static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd,
 		unsigned int issue_flags)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->cmd;
+	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
 	struct ublk_device *ub = NULL;
 	int ret = -EINVAL;
 
diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
index d24ea2e05156..836257b9af6f 100644
--- a/drivers/nvme/host/ioctl.c
+++ b/drivers/nvme/host/ioctl.c
@@ -458,6 +458,12 @@ struct nvme_uring_cmd_pdu {
 	} u;
 };
 
+static inline struct nvme_uring_cmd *nvme_uring_cmd(
+		struct io_uring_cmd *ioucmd)
+{
+	return (struct nvme_uring_cmd *)ioucmd->sqe->cmd;
+}
+
 static inline struct nvme_uring_cmd_pdu *nvme_uring_cmd_pdu(
 		struct io_uring_cmd *ioucmd)
 {
@@ -552,7 +558,7 @@ static int nvme_uring_cmd_io(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
 		struct io_uring_cmd *ioucmd, unsigned int issue_flags, bool vec)
 {
 	struct nvme_uring_cmd_pdu *pdu = nvme_uring_cmd_pdu(ioucmd);
-	const struct nvme_uring_cmd *cmd = ioucmd->cmd;
+	const struct nvme_uring_cmd *cmd = nvme_uring_cmd(ioucmd);
 	struct request_queue *q = ns ? ns->queue : ctrl->admin_q;
 	struct nvme_uring_data d;
 	struct nvme_command c;
diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
index 35b9328ca335..2dfc81dd6d1a 100644
--- a/include/linux/io_uring.h
+++ b/include/linux/io_uring.h
@@ -24,7 +24,7 @@ enum io_uring_cmd_flags {
 
 struct io_uring_cmd {
 	struct file	*file;
-	const void	*cmd;
+	const struct io_uring_sqe *sqe;
 	union {
 		/* callback to defer completions to task context */
 		void (*task_work_cb)(struct io_uring_cmd *cmd, unsigned);
diff --git a/io_uring/opdef.c b/io_uring/opdef.c
index cca7c5b55208..3b9c6489b8b6 100644
--- a/io_uring/opdef.c
+++ b/io_uring/opdef.c
@@ -627,7 +627,7 @@ const struct io_cold_def io_cold_defs[] = {
 	},
 	[IORING_OP_URING_CMD] = {
 		.name			= "URING_CMD",
-		.async_size		= uring_cmd_pdu_size(1),
+		.async_size		= 2 * sizeof(struct io_uring_sqe),
 		.prep_async		= io_uring_cmd_prep_async,
 	},
 	[IORING_OP_SEND_ZC] = {
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index 5113c9a48583..a1be746cd009 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -69,15 +69,13 @@ EXPORT_SYMBOL_GPL(io_uring_cmd_done);
 int io_uring_cmd_prep_async(struct io_kiocb *req)
 {
 	struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
-	size_t cmd_size;
+	size_t size = uring_sqe_size(req->ctx);
 
 	BUILD_BUG_ON(uring_cmd_pdu_size(0) != 16);
 	BUILD_BUG_ON(uring_cmd_pdu_size(1) != 80);
 
-	cmd_size = uring_cmd_pdu_size(req->ctx->flags & IORING_SETUP_SQE128);
-
-	memcpy(req->async_data, ioucmd->cmd, cmd_size);
-	ioucmd->cmd = req->async_data;
+	memcpy(req->async_data, ioucmd->sqe, size);
+	ioucmd->sqe = req->async_data;
 	return 0;
 }
 
@@ -103,7 +101,7 @@ int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		req->imu = ctx->user_bufs[index];
 		io_req_set_rsrc_node(req, ctx, 0);
 	}
-	ioucmd->cmd = sqe->cmd;
+	ioucmd->sqe = sqe;
 	ioucmd->cmd_op = READ_ONCE(sqe->cmd_op);
 	return 0;
 }
-- 
2.34.1

Re: [PATCH v3 2/4] io_uring: Pass whole sqe to commands

[Christoph Hellwig]

>  static int ublk_ch_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
>  {
> -	struct ublksrv_io_cmd *ub_cmd = (struct ublksrv_io_cmd *)cmd->cmd;
> +	struct ublksrv_io_cmd *ub_cmd = (struct ublksrv_io_cmd *)cmd->sqe->cmd;

This still adds all the crazy casting!!

As I already explained two times, last time including actual working
code, please add a helper that takes a io_uring_cmd * argument, and
returns cmd->sqe->cmd with a void * type.  With that all the casting
can be removed.

[PATCH v3 3/4] io_uring: Remove unnecessary BUILD_BUG_ON

[Breno Leitao]

In the io_uring_cmd_prep_async() there is an unnecessary compilation time
check to check if cmd is correctly placed at field 48 of the SQE.

This is unnecessary, since this check is already in place at
io_uring_init():

          BUILD_BUG_SQE_ELEM(48, __u64,  addr3);

Remove it and the uring_cmd_pdu_size() function, which is not used
anymore.

Keith started a discussion about this topic in the following thread:
Link: https://lore.kernel.org/lkml/ZDBmQOhbyU0iLhMw@kbusch-mbp.dhcp.thefacebook.com/

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 io_uring/uring_cmd.c | 3 ---
 io_uring/uring_cmd.h | 8 --------
 2 files changed, 11 deletions(-)

diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index a1be746cd009..743d1496431b 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -71,9 +71,6 @@ int io_uring_cmd_prep_async(struct io_kiocb *req)
 	struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
 	size_t size = uring_sqe_size(req->ctx);
 
-	BUILD_BUG_ON(uring_cmd_pdu_size(0) != 16);
-	BUILD_BUG_ON(uring_cmd_pdu_size(1) != 80);
-
 	memcpy(req->async_data, ioucmd->sqe, size);
 	ioucmd->sqe = req->async_data;
 	return 0;
diff --git a/io_uring/uring_cmd.h b/io_uring/uring_cmd.h
index 7c6697d13cb2..8117684ec3ca 100644
--- a/io_uring/uring_cmd.h
+++ b/io_uring/uring_cmd.h
@@ -3,11 +3,3 @@
 int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags);
 int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
 int io_uring_cmd_prep_async(struct io_kiocb *req);
-
-/*
- * The URING_CMD payload starts at 'cmd' in the first sqe, and continues into
- * the following sqe if SQE128 is used.
- */
-#define uring_cmd_pdu_size(is_sqe128)				\
-	((1 + !!(is_sqe128)) * sizeof(struct io_uring_sqe) -	\
-		offsetof(struct io_uring_sqe, cmd))
-- 
2.34.1

[PATCH v3 4/4] block: ublk_drv: Add a helper instead of casting

[Breno Leitao]

ublk driver is using casts to get private data from uring cmd struct.
Let's use a proper helper, as an interface that requires casts in all
callers is one asking for bugs.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Breno Leitao <leitao@debian.org>
---
 drivers/block/ublk_drv.c | 36 ++++++++++++++++++++++++------------
 1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index ec23a3c9fac8..1fa6a4d54d6d 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -1261,9 +1261,21 @@ static void ublk_handle_need_get_data(struct ublk_device *ub, int q_id,
 	ublk_queue_cmd(ubq, req);
 }
 
+static inline struct ublksrv_ctrl_cmd *ublk_uring_ctrl_cmd(
+		struct io_uring_cmd *cmd)
+{
+	return (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
+}
+
+static inline struct ublksrv_io_cmd *ublk_uring_io_cmd(
+		struct io_uring_cmd *cmd)
+{
+	return (struct ublksrv_io_cmd *)cmd->sqe->cmd;
+}
+
 static int ublk_ch_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
 {
-	struct ublksrv_io_cmd *ub_cmd = (struct ublksrv_io_cmd *)cmd->sqe->cmd;
+	struct ublksrv_io_cmd *ub_cmd = ublk_uring_io_cmd(cmd);
 	struct ublk_device *ub = cmd->file->private_data;
 	struct ublk_queue *ubq;
 	struct ublk_io *io;
@@ -1567,7 +1579,7 @@ static struct ublk_device *ublk_get_device_from_id(int idx)
 
 static int ublk_ctrl_start_dev(struct ublk_device *ub, struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
+	struct ublksrv_ctrl_cmd *header = ublk_uring_ctrl_cmd(cmd);
 	int ublksrv_pid = (int)header->data[0];
 	struct gendisk *disk;
 	int ret = -EINVAL;
@@ -1630,7 +1642,7 @@ static int ublk_ctrl_start_dev(struct ublk_device *ub, struct io_uring_cmd *cmd)
 static int ublk_ctrl_get_queue_affinity(struct ublk_device *ub,
 		struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
+	struct ublksrv_ctrl_cmd *header = ublk_uring_ctrl_cmd(cmd);
 	void __user *argp = (void __user *)(unsigned long)header->addr;
 	cpumask_var_t cpumask;
 	unsigned long queue;
@@ -1681,7 +1693,7 @@ static inline void ublk_dump_dev_info(struct ublksrv_ctrl_dev_info *info)
 
 static int ublk_ctrl_add_dev(struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
+	struct ublksrv_ctrl_cmd *header = ublk_uring_ctrl_cmd(cmd);
 	void __user *argp = (void __user *)(unsigned long)header->addr;
 	struct ublksrv_ctrl_dev_info info;
 	struct ublk_device *ub;
@@ -1844,7 +1856,7 @@ static int ublk_ctrl_del_dev(struct ublk_device **p_ub)
 
 static inline void ublk_ctrl_cmd_dump(struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
+	struct ublksrv_ctrl_cmd *header = ublk_uring_ctrl_cmd(cmd);
 
 	pr_devel("%s: cmd_op %x, dev id %d qid %d data %llx buf %llx len %u\n",
 			__func__, cmd->cmd_op, header->dev_id, header->queue_id,
@@ -1863,7 +1875,7 @@ static int ublk_ctrl_stop_dev(struct ublk_device *ub)
 static int ublk_ctrl_get_dev_info(struct ublk_device *ub,
 		struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
+	struct ublksrv_ctrl_cmd *header = ublk_uring_ctrl_cmd(cmd);
 	void __user *argp = (void __user *)(unsigned long)header->addr;
 
 	if (header->len < sizeof(struct ublksrv_ctrl_dev_info) || !header->addr)
@@ -1894,7 +1906,7 @@ static void ublk_ctrl_fill_params_devt(struct ublk_device *ub)
 static int ublk_ctrl_get_params(struct ublk_device *ub,
 		struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
+	struct ublksrv_ctrl_cmd *header = ublk_uring_ctrl_cmd(cmd);
 	void __user *argp = (void __user *)(unsigned long)header->addr;
 	struct ublk_params_header ph;
 	int ret;
@@ -1925,7 +1937,7 @@ static int ublk_ctrl_get_params(struct ublk_device *ub,
 static int ublk_ctrl_set_params(struct ublk_device *ub,
 		struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
+	struct ublksrv_ctrl_cmd *header = ublk_uring_ctrl_cmd(cmd);
 	void __user *argp = (void __user *)(unsigned long)header->addr;
 	struct ublk_params_header ph;
 	int ret = -EFAULT;
@@ -1983,7 +1995,7 @@ static void ublk_queue_reinit(struct ublk_device *ub, struct ublk_queue *ubq)
 static int ublk_ctrl_start_recovery(struct ublk_device *ub,
 		struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
+	struct ublksrv_ctrl_cmd *header = ublk_uring_ctrl_cmd(cmd);
 	int ret = -EINVAL;
 	int i;
 
@@ -2025,7 +2037,7 @@ static int ublk_ctrl_start_recovery(struct ublk_device *ub,
 static int ublk_ctrl_end_recovery(struct ublk_device *ub,
 		struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
+	struct ublksrv_ctrl_cmd *header = ublk_uring_ctrl_cmd(cmd);
 	int ublksrv_pid = (int)header->data[0];
 	int ret = -EINVAL;
 
@@ -2092,7 +2104,7 @@ static int ublk_char_dev_permission(struct ublk_device *ub,
 static int ublk_ctrl_uring_cmd_permission(struct ublk_device *ub,
 		struct io_uring_cmd *cmd)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
+	struct ublksrv_ctrl_cmd *header = ublk_uring_ctrl_cmd(cmd);
 	bool unprivileged = ub->dev_info.flags & UBLK_F_UNPRIVILEGED_DEV;
 	void __user *argp = (void __user *)(unsigned long)header->addr;
 	char *dev_path = NULL;
@@ -2171,7 +2183,7 @@ static int ublk_ctrl_uring_cmd_permission(struct ublk_device *ub,
 static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd,
 		unsigned int issue_flags)
 {
-	struct ublksrv_ctrl_cmd *header = (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
+	struct ublksrv_ctrl_cmd *header = ublk_uring_ctrl_cmd(cmd);
 	struct ublk_device *ub = NULL;
 	int ret = -EINVAL;
 
-- 
2.34.1

Re: [PATCH v3 4/4] block: ublk_drv: Add a helper instead of casting

[Christoph Hellwig]

On Sun, Apr 30, 2023 at 07:35:32AM -0700, Breno Leitao wrote:
> ublk driver is using casts to get private data from uring cmd struct.
> Let's use a proper helper, as an interface that requires casts in all
> callers is one asking for bugs.
> 
> Suggested-by: Christoph Hellwig <hch@lst.de>

No, I've not suggested this.

> +static inline struct ublksrv_ctrl_cmd *ublk_uring_ctrl_cmd(
> +		struct io_uring_cmd *cmd)
> +{
> +	return (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
> +}

I've two times explained we need a core io_uring helper to remove this
casting in the drivers, and I've explained how to do that and provided
the actual code for it.

Re: [PATCH v3 4/4] block: ublk_drv: Add a helper instead of casting

[Breno Leitao]

On Mon, May 01, 2023 at 06:31:22AM +0200, Christoph Hellwig wrote:
> On Sun, Apr 30, 2023 at 07:35:32AM -0700, Breno Leitao wrote:
> > ublk driver is using casts to get private data from uring cmd struct.
> > Let's use a proper helper, as an interface that requires casts in all
> > callers is one asking for bugs.
> > 
> > Suggested-by: Christoph Hellwig <hch@lst.de>
> 
> No, I've not suggested this.
> 
> > +static inline struct ublksrv_ctrl_cmd *ublk_uring_ctrl_cmd(
> > +		struct io_uring_cmd *cmd)
> > +{
> > +	return (struct ublksrv_ctrl_cmd *)cmd->sqe->cmd;
> > +}
> 
> I've two times explained we need a core io_uring helper to remove this
> casting in the drivers, and I've explained how to do that and provided
> the actual code for it.

Sorry for it, somehow I misunderstood what you meant. I re-read the
thread and got what you said.

I am preparing a V4 with the new approach, and I will send it tomorrow.