[PATCH V4 0/2] io_uring: cancelable uring_cmd

[PATCH V4 0/2] io_uring: cancelable uring_cmd

[Ming Lei]

Hello,

Patch 1 retains top 8bits of  uring_cmd flags for kernel internal use.

Patch 2 implements cancelable uring_cmd.

git tree(with ublk change)

	https://github.com/ming1/linux/commits/uring_exit_and_ublk

V4:
	- return -EINVAL in case that internal bits are set
	- replace static lock checker with lockdep_assert_held(&ctx->uring_lock);

V3:
	- code style change as suggested by Jens
	- add patch 1

V2:
	- use ->uring_cmd() with IO_URING_F_CANCEL for canceling command


Ming Lei (2):
  io_uring: retain top 8bits of uring_cmd flags for kernel internal use
  io_uring: cancelable uring_cmd

 include/linux/io_uring.h       | 19 +++++++++++++
 include/linux/io_uring_types.h |  6 ++++
 include/uapi/linux/io_uring.h  |  5 ++--
 io_uring/io_uring.c            | 39 ++++++++++++++++++++++++++
 io_uring/uring_cmd.c           | 51 +++++++++++++++++++++++++++++++++-
 5 files changed, 116 insertions(+), 4 deletions(-)

-- 
2.41.0

[PATCH V4 1/2] io_uring: retain top 8bits of uring_cmd flags for kernel internal use

[Ming Lei]

Retain top 8bits of uring_cmd flags for kernel internal use, so that we
can move IORING_URING_CMD_POLLED out of uapi header.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 include/linux/io_uring.h      | 3 +++
 include/uapi/linux/io_uring.h | 5 ++---
 io_uring/io_uring.c           | 3 +++
 io_uring/uring_cmd.c          | 2 +-
 4 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
index 106cdc55ff3b..ae08d6f66e62 100644
--- a/include/linux/io_uring.h
+++ b/include/linux/io_uring.h
@@ -22,6 +22,9 @@ enum io_uring_cmd_flags {
 	IO_URING_F_IOPOLL		= (1 << 10),
 };
 
+/* only top 8 bits of sqe->uring_cmd_flags for kernel internal use */
+#define IORING_URING_CMD_POLLED		(1U << 31)
+
 struct io_uring_cmd {
 	struct file	*file;
 	const struct io_uring_sqe *sqe;
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 8e61f8b7c2ce..de77ad08b123 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -246,13 +246,12 @@ enum io_uring_op {
 };
 
 /*
- * sqe->uring_cmd_flags
+ * sqe->uring_cmd_flags		top 8bits aren't available for userspace
  * IORING_URING_CMD_FIXED	use registered buffer; pass this flag
  *				along with setting sqe->buf_index.
- * IORING_URING_CMD_POLLED	driver use only
  */
 #define IORING_URING_CMD_FIXED	(1U << 0)
-#define IORING_URING_CMD_POLLED	(1U << 31)
+#define IORING_URING_CMD_MASK	IORING_URING_CMD_FIXED
 
 
 /*
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 783ed0fff71b..9aedb7202403 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -4666,6 +4666,9 @@ static int __init io_uring_init(void)
 
 	BUILD_BUG_ON(sizeof(atomic_t) != sizeof(u32));
 
+	/* top 8bits are for internal use */
+	BUILD_BUG_ON((IORING_URING_CMD_MASK & 0xff000000) != 0);
+
 	io_uring_optable_init();
 
 	/*
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index 537795fddc87..a0b0ec5473bf 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -91,7 +91,7 @@ int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		return -EINVAL;
 
 	ioucmd->flags = READ_ONCE(sqe->uring_cmd_flags);
-	if (ioucmd->flags & ~IORING_URING_CMD_FIXED)
+	if (ioucmd->flags & ~IORING_URING_CMD_MASK)
 		return -EINVAL;
 
 	if (ioucmd->flags & IORING_URING_CMD_FIXED) {
-- 
2.41.0

[PATCH V4 2/2] io_uring: cancelable uring_cmd

[Ming Lei]

uring_cmd may never complete, such as ublk, in which uring cmd isn't
completed until one new block request is coming from ublk block device.

Add cancelable uring_cmd to provide mechanism to driver for cancelling
pending commands in its own way.

Add API of io_uring_cmd_mark_cancelable() for driver to mark one command as
cancelable, then io_uring will cancel this command in
io_uring_cancel_generic(). ->uring_cmd() callback is reused for canceling
command in driver's way, then driver gets notified with the cancelling
from io_uring.

Add API of io_uring_cmd_get_task() to help driver cancel handler
deal with the canceling.

Cc: Gabriel Krisman Bertazi <krisman@suse.de>
Suggested-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 include/linux/io_uring.h       | 16 +++++++++++
 include/linux/io_uring_types.h |  6 +++++
 io_uring/io_uring.c            | 36 +++++++++++++++++++++++++
 io_uring/uring_cmd.c           | 49 ++++++++++++++++++++++++++++++++++
 4 files changed, 107 insertions(+)

diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
index ae08d6f66e62..a0307289bdc7 100644
--- a/include/linux/io_uring.h
+++ b/include/linux/io_uring.h
@@ -20,9 +20,13 @@ enum io_uring_cmd_flags {
 	IO_URING_F_SQE128		= (1 << 8),
 	IO_URING_F_CQE32		= (1 << 9),
 	IO_URING_F_IOPOLL		= (1 << 10),
+
+	/* set when uring wants to cancel one issued command */
+	IO_URING_F_CANCEL		= (1 << 11),
 };
 
 /* only top 8 bits of sqe->uring_cmd_flags for kernel internal use */
+#define IORING_URING_CMD_CANCELABLE	(1U << 30)
 #define IORING_URING_CMD_POLLED		(1U << 31)
 
 struct io_uring_cmd {
@@ -85,6 +89,9 @@ static inline void io_uring_free(struct task_struct *tsk)
 		__io_uring_free(tsk);
 }
 int io_uring_cmd_sock(struct io_uring_cmd *cmd, unsigned int issue_flags);
+int io_uring_cmd_mark_cancelable(struct io_uring_cmd *cmd,
+		unsigned int issue_flags);
+struct task_struct *io_uring_cmd_get_task(struct io_uring_cmd *cmd);
 #else
 static inline int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
 			      struct iov_iter *iter, void *ioucmd)
@@ -125,6 +132,15 @@ static inline int io_uring_cmd_sock(struct io_uring_cmd *cmd,
 {
 	return -EOPNOTSUPP;
 }
+static inline int io_uring_cmd_mark_cancelable(struct io_uring_cmd *cmd,
+		unsigned int issue_flags)
+{
+	return -EOPNOTSUPP;
+}
+static inline struct task_struct *io_uring_cmd_get_task(struct io_uring_cmd *cmd)
+{
+	return NULL;
+}
 #endif
 
 #endif
diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index 13d19b9be9f4..1571db76bec1 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -265,6 +265,12 @@ struct io_ring_ctx {
 		 */
 		struct io_wq_work_list	iopoll_list;
 		bool			poll_multi_queue;
+
+		/*
+		 * Any cancelable uring_cmd is added to this list in
+		 * ->uring_cmd() by io_uring_cmd_insert_cancelable()
+		 */
+		struct hlist_head	cancelable_uring_cmd;
 	} ____cacheline_aligned_in_smp;
 
 	struct {
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 9aedb7202403..9c90cad39059 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -350,6 +350,7 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 	INIT_WQ_LIST(&ctx->locked_free_list);
 	INIT_DELAYED_WORK(&ctx->fallback_work, io_fallback_req_func);
 	INIT_WQ_LIST(&ctx->submit_state.compl_reqs);
+	INIT_HLIST_HEAD(&ctx->cancelable_uring_cmd);
 	return ctx;
 err:
 	kfree(ctx->cancel_table.hbs);
@@ -3256,6 +3257,40 @@ static __cold bool io_uring_try_cancel_iowq(struct io_ring_ctx *ctx)
 	return ret;
 }
 
+static bool io_uring_try_cancel_uring_cmd(struct io_ring_ctx *ctx,
+		struct task_struct *task, bool cancel_all)
+{
+	struct hlist_node *tmp;
+	struct io_kiocb *req;
+	bool ret = false;
+
+	lockdep_assert_held(&ctx->uring_lock);
+
+	hlist_for_each_entry_safe(req, tmp, &ctx->cancelable_uring_cmd,
+			hash_node) {
+		struct io_uring_cmd *cmd = io_kiocb_to_cmd(req,
+				struct io_uring_cmd);
+		struct file *file = req->file;
+
+		if (WARN_ON_ONCE(!file->f_op->uring_cmd))
+			continue;
+
+		if (!cancel_all && req->task != task)
+			continue;
+
+		if (cmd->flags & IORING_URING_CMD_CANCELABLE) {
+			/* ->sqe isn't available if no async data */
+			if (!req_has_async_data(req))
+				cmd->sqe = NULL;
+			file->f_op->uring_cmd(cmd, IO_URING_F_CANCEL);
+			ret = true;
+		}
+	}
+	io_submit_flush_completions(ctx);
+
+	return ret;
+}
+
 static __cold bool io_uring_try_cancel_requests(struct io_ring_ctx *ctx,
 						struct task_struct *task,
 						bool cancel_all)
@@ -3303,6 +3338,7 @@ static __cold bool io_uring_try_cancel_requests(struct io_ring_ctx *ctx,
 	ret |= io_cancel_defer_files(ctx, task, cancel_all);
 	mutex_lock(&ctx->uring_lock);
 	ret |= io_poll_remove_all(ctx, task, cancel_all);
+	ret |= io_uring_try_cancel_uring_cmd(ctx, task, cancel_all);
 	mutex_unlock(&ctx->uring_lock);
 	ret |= io_kill_timeouts(ctx, task, cancel_all);
 	if (task)
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index a0b0ec5473bf..f2cbfa7f1f7f 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -13,6 +13,53 @@
 #include "rsrc.h"
 #include "uring_cmd.h"
 
+static void io_uring_cmd_del_cancelable(struct io_uring_cmd *cmd,
+		unsigned int issue_flags)
+{
+	struct io_kiocb *req = cmd_to_io_kiocb(cmd);
+	struct io_ring_ctx *ctx = req->ctx;
+
+	if (!(cmd->flags & IORING_URING_CMD_CANCELABLE))
+		return;
+
+	cmd->flags &= ~IORING_URING_CMD_CANCELABLE;
+	io_ring_submit_lock(ctx, issue_flags);
+	hlist_del(&req->hash_node);
+	io_ring_submit_unlock(ctx, issue_flags);
+}
+
+/*
+ * Mark this command as concelable, then io_uring_try_cancel_uring_cmd()
+ * will try to cancel this issued command by sending ->uring_cmd() with
+ * issue_flags of IO_URING_F_CANCEL.
+ *
+ * The command is guaranteed to not be done when calling ->uring_cmd()
+ * with IO_URING_F_CANCEL, but it is driver's responsibility to deal
+ * with race between io_uring canceling and normal completion.
+ */
+int io_uring_cmd_mark_cancelable(struct io_uring_cmd *cmd,
+		unsigned int issue_flags)
+{
+	struct io_kiocb *req = cmd_to_io_kiocb(cmd);
+	struct io_ring_ctx *ctx = req->ctx;
+
+	if (!(cmd->flags & IORING_URING_CMD_CANCELABLE)) {
+		cmd->flags |= IORING_URING_CMD_CANCELABLE;
+		io_ring_submit_lock(ctx, issue_flags);
+		hlist_add_head(&req->hash_node, &ctx->cancelable_uring_cmd);
+		io_ring_submit_unlock(ctx, issue_flags);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(io_uring_cmd_mark_cancelable);
+
+struct task_struct *io_uring_cmd_get_task(struct io_uring_cmd *cmd)
+{
+	return cmd_to_io_kiocb(cmd)->task;
+}
+EXPORT_SYMBOL_GPL(io_uring_cmd_get_task);
+
 static void io_uring_cmd_work(struct io_kiocb *req, struct io_tw_state *ts)
 {
 	struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
@@ -56,6 +103,8 @@ void io_uring_cmd_done(struct io_uring_cmd *ioucmd, ssize_t ret, ssize_t res2,
 {
 	struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);
 
+	io_uring_cmd_del_cancelable(ioucmd, issue_flags);
+
 	if (ret < 0)
 		req_set_fail(req);
 
-- 
2.41.0

Re: [PATCH V4 2/2] io_uring: cancelable uring_cmd

[Gabriel Krisman Bertazi]

Ming Lei <ming.lei@redhat.com> writes:

> uring_cmd may never complete, such as ublk, in which uring cmd isn't
> completed until one new block request is coming from ublk block device.
>
> Add cancelable uring_cmd to provide mechanism to driver for cancelling
> pending commands in its own way.
>
> Add API of io_uring_cmd_mark_cancelable() for driver to mark one command as
> cancelable, then io_uring will cancel this command in
> io_uring_cancel_generic(). ->uring_cmd() callback is reused for canceling
> command in driver's way, then driver gets notified with the cancelling
> from io_uring.
>
> Add API of io_uring_cmd_get_task() to help driver cancel handler
> deal with the canceling.

I think using ->uring_cmd() with IO_URING_F_CANCEL looks much
nicer. thanks for that.

Reviewed-by: Gabriel Krisman Bertazi <krisman@suse.de>


-- 
Gabriel Krisman Bertazi

Re: [PATCH V4 1/2] io_uring: retain top 8bits of uring_cmd flags for kernel internal use

[Gabriel Krisman Bertazi]

Ming Lei <ming.lei@redhat.com> writes:

> Retain top 8bits of uring_cmd flags for kernel internal use, so that we
> can move IORING_URING_CMD_POLLED out of uapi header.

Feel free to add:

Reviewed-by: Gabriel Krisman Bertazi <krisman@suse.de>

>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  include/linux/io_uring.h      | 3 +++
>  include/uapi/linux/io_uring.h | 5 ++---
>  io_uring/io_uring.c           | 3 +++
>  io_uring/uring_cmd.c          | 2 +-
>  4 files changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
> index 106cdc55ff3b..ae08d6f66e62 100644
> --- a/include/linux/io_uring.h
> +++ b/include/linux/io_uring.h
> @@ -22,6 +22,9 @@ enum io_uring_cmd_flags {
>  	IO_URING_F_IOPOLL		= (1 << 10),
>  };
>  
> +/* only top 8 bits of sqe->uring_cmd_flags for kernel internal use */
> +#define IORING_URING_CMD_POLLED		(1U << 31)
> +
>  struct io_uring_cmd {
>  	struct file	*file;
>  	const struct io_uring_sqe *sqe;
> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
> index 8e61f8b7c2ce..de77ad08b123 100644
> --- a/include/uapi/linux/io_uring.h
> +++ b/include/uapi/linux/io_uring.h
> @@ -246,13 +246,12 @@ enum io_uring_op {
>  };
>  
>  /*
> - * sqe->uring_cmd_flags
> + * sqe->uring_cmd_flags		top 8bits aren't available for userspace
>   * IORING_URING_CMD_FIXED	use registered buffer; pass this flag
>   *				along with setting sqe->buf_index.
> - * IORING_URING_CMD_POLLED	driver use only
>   */
>  #define IORING_URING_CMD_FIXED	(1U << 0)
> -#define IORING_URING_CMD_POLLED	(1U << 31)
> +#define IORING_URING_CMD_MASK	IORING_URING_CMD_FIXED
>  
>  
>  /*
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index 783ed0fff71b..9aedb7202403 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -4666,6 +4666,9 @@ static int __init io_uring_init(void)
>  
>  	BUILD_BUG_ON(sizeof(atomic_t) != sizeof(u32));
>  
> +	/* top 8bits are for internal use */
> +	BUILD_BUG_ON((IORING_URING_CMD_MASK & 0xff000000) != 0);
> +
>  	io_uring_optable_init();
>  
>  	/*
> diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
> index 537795fddc87..a0b0ec5473bf 100644
> --- a/io_uring/uring_cmd.c
> +++ b/io_uring/uring_cmd.c
> @@ -91,7 +91,7 @@ int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>  		return -EINVAL;
>  
>  	ioucmd->flags = READ_ONCE(sqe->uring_cmd_flags);
> -	if (ioucmd->flags & ~IORING_URING_CMD_FIXED)
> +	if (ioucmd->flags & ~IORING_URING_CMD_MASK)
>  		return -EINVAL;
>  
>  	if (ioucmd->flags & IORING_URING_CMD_FIXED) {

-- 
Gabriel Krisman Bertazi

Re: [PATCH V4 1/2] io_uring: retain top 8bits of uring_cmd flags for kernel internal use

[Anuj Gupta]

[-- Attachment #1: Type: text/plain, Size: 2515 bytes --]

On 23/09/23 10:50AM, Ming Lei wrote:
>Retain top 8bits of uring_cmd flags for kernel internal use, so that we
>can move IORING_URING_CMD_POLLED out of uapi header.
>

Looks good.

Reviewed-by: Anuj Gupta <anuj20.g@samsung.com>

>Signed-off-by: Ming Lei <ming.lei@redhat.com>
>---
> include/linux/io_uring.h      | 3 +++
> include/uapi/linux/io_uring.h | 5 ++---
> io_uring/io_uring.c           | 3 +++
> io_uring/uring_cmd.c          | 2 +-
> 4 files changed, 9 insertions(+), 4 deletions(-)
>
>diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
>index 106cdc55ff3b..ae08d6f66e62 100644
>--- a/include/linux/io_uring.h
>+++ b/include/linux/io_uring.h
>@@ -22,6 +22,9 @@ enum io_uring_cmd_flags {
> 	IO_URING_F_IOPOLL		= (1 << 10),
> };
>
>+/* only top 8 bits of sqe->uring_cmd_flags for kernel internal use */
>+#define IORING_URING_CMD_POLLED		(1U << 31)
>+
> struct io_uring_cmd {
> 	struct file	*file;
> 	const struct io_uring_sqe *sqe;
>diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
>index 8e61f8b7c2ce..de77ad08b123 100644
>--- a/include/uapi/linux/io_uring.h
>+++ b/include/uapi/linux/io_uring.h
>@@ -246,13 +246,12 @@ enum io_uring_op {
> };
>
> /*
>- * sqe->uring_cmd_flags
>+ * sqe->uring_cmd_flags		top 8bits aren't available for userspace
>  * IORING_URING_CMD_FIXED	use registered buffer; pass this flag
>  *				along with setting sqe->buf_index.
>- * IORING_URING_CMD_POLLED	driver use only
>  */
> #define IORING_URING_CMD_FIXED	(1U << 0)
>-#define IORING_URING_CMD_POLLED	(1U << 31)
>+#define IORING_URING_CMD_MASK	IORING_URING_CMD_FIXED
>
>
> /*
>diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
>index 783ed0fff71b..9aedb7202403 100644
>--- a/io_uring/io_uring.c
>+++ b/io_uring/io_uring.c
>@@ -4666,6 +4666,9 @@ static int __init io_uring_init(void)
>
> 	BUILD_BUG_ON(sizeof(atomic_t) != sizeof(u32));
>
>+	/* top 8bits are for internal use */
>+	BUILD_BUG_ON((IORING_URING_CMD_MASK & 0xff000000) != 0);
>+
> 	io_uring_optable_init();
>
> 	/*
>diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
>index 537795fddc87..a0b0ec5473bf 100644
>--- a/io_uring/uring_cmd.c
>+++ b/io_uring/uring_cmd.c
>@@ -91,7 +91,7 @@ int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
> 		return -EINVAL;
>
> 	ioucmd->flags = READ_ONCE(sqe->uring_cmd_flags);
>-	if (ioucmd->flags & ~IORING_URING_CMD_FIXED)
>+	if (ioucmd->flags & ~IORING_URING_CMD_MASK)
> 		return -EINVAL;
>
> 	if (ioucmd->flags & IORING_URING_CMD_FIXED) {
>-- 
>2.41.0
>

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Re: [PATCH V4 2/2] io_uring: cancelable uring_cmd

[Jens Axboe]

On 9/22/23 8:50 PM, Ming Lei wrote:
> diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
> index ae08d6f66e62..a0307289bdc7 100644
> --- a/include/linux/io_uring.h
> +++ b/include/linux/io_uring.h
> @@ -20,9 +20,13 @@ enum io_uring_cmd_flags {
>  	IO_URING_F_SQE128		= (1 << 8),
>  	IO_URING_F_CQE32		= (1 << 9),
>  	IO_URING_F_IOPOLL		= (1 << 10),
> +
> +	/* set when uring wants to cancel one issued command */
> +	IO_URING_F_CANCEL		= (1 << 11),
>  };

I'd make that comment:

/* set when uring wants to cancel a previously issued command */

> @@ -125,6 +132,15 @@ static inline int io_uring_cmd_sock(struct io_uring_cmd *cmd,
>  {
>  	return -EOPNOTSUPP;
>  }
> +static inline int io_uring_cmd_mark_cancelable(struct io_uring_cmd *cmd,
> +		unsigned int issue_flags)
> +{
> +	return -EOPNOTSUPP;
> +}

Do we need this to return an error? Presumably this will never get
called if IO_URING isn't defined, but if it does, it obviously doesn't
need to do anything anyway. Seems like it should just be a void, and
ditto for the enabled version which can't return an error anyway.

>  	return ret;
>  }
>  
> +static bool io_uring_try_cancel_uring_cmd(struct io_ring_ctx *ctx,
> +		struct task_struct *task, bool cancel_all)
> +{
> +	struct hlist_node *tmp;
> +	struct io_kiocb *req;
> +	bool ret = false;
> +
> +	lockdep_assert_held(&ctx->uring_lock);
> +
> +	hlist_for_each_entry_safe(req, tmp, &ctx->cancelable_uring_cmd,
> +			hash_node) {
> +		struct io_uring_cmd *cmd = io_kiocb_to_cmd(req,
> +				struct io_uring_cmd);
> +		struct file *file = req->file;
> +
> +		if (WARN_ON_ONCE(!file->f_op->uring_cmd))
> +			continue;

That check belongs in the function that marks it cancelable and adds it
to the list.

Outside of those minor nits, looks fine to me, and patch 1 does too.

-- 
Jens Axboe

Re: [PATCH V4 2/2] io_uring: cancelable uring_cmd

[Ming Lei]

On Thu, Sep 28, 2023 at 02:38:32AM -0600, Jens Axboe wrote:
> On 9/22/23 8:50 PM, Ming Lei wrote:
> > diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
> > index ae08d6f66e62..a0307289bdc7 100644
> > --- a/include/linux/io_uring.h
> > +++ b/include/linux/io_uring.h
> > @@ -20,9 +20,13 @@ enum io_uring_cmd_flags {
> >  	IO_URING_F_SQE128		= (1 << 8),
> >  	IO_URING_F_CQE32		= (1 << 9),
> >  	IO_URING_F_IOPOLL		= (1 << 10),
> > +
> > +	/* set when uring wants to cancel one issued command */
> > +	IO_URING_F_CANCEL		= (1 << 11),
> >  };
> 
> I'd make that comment:
> 
> /* set when uring wants to cancel a previously issued command */

OK.

> 
> > @@ -125,6 +132,15 @@ static inline int io_uring_cmd_sock(struct io_uring_cmd *cmd,
> >  {
> >  	return -EOPNOTSUPP;
> >  }
> > +static inline int io_uring_cmd_mark_cancelable(struct io_uring_cmd *cmd,
> > +		unsigned int issue_flags)
> > +{
> > +	return -EOPNOTSUPP;
> > +}
> 
> Do we need this to return an error? Presumably this will never get
> called if IO_URING isn't defined, but if it does, it obviously doesn't
> need to do anything anyway. Seems like it should just be a void, and
> ditto for the enabled version which can't return an error anyway.

Indeed, 'void' is better.

> 
> >  	return ret;
> >  }
> >  
> > +static bool io_uring_try_cancel_uring_cmd(struct io_ring_ctx *ctx,
> > +		struct task_struct *task, bool cancel_all)
> > +{
> > +	struct hlist_node *tmp;
> > +	struct io_kiocb *req;
> > +	bool ret = false;
> > +
> > +	lockdep_assert_held(&ctx->uring_lock);
> > +
> > +	hlist_for_each_entry_safe(req, tmp, &ctx->cancelable_uring_cmd,
> > +			hash_node) {
> > +		struct io_uring_cmd *cmd = io_kiocb_to_cmd(req,
> > +				struct io_uring_cmd);
> > +		struct file *file = req->file;
> > +
> > +		if (WARN_ON_ONCE(!file->f_op->uring_cmd))
> > +			continue;
> 
> That check belongs in the function that marks it cancelable and adds it
> to the list.

io_uring_cmd_mark_cancelable() is actually called from ->uring_cmd(), so
the check isn't necessary.



thanks,
Ming