[for-next,v11,02/13] io_uring: introduce fixed buffer support for io_uring_cmd

Commit Message

Anuj Gupta Sept. 29, 2022, 12:06 p.m. UTC

Add IORING_URING_CMD_FIXED flag that is to be used for sending io_uring
command with previously registered buffers. User-space passes the buffer
index in sqe->buf_index, same as done in read/write variants that uses
fixed buffers.

Signed-off-by: Anuj Gupta <[e-mail]>
Signed-off-by: Kanchan Joshi <[e-mail]>
---
 include/linux/io_uring.h      |  2 +-
 include/uapi/linux/io_uring.h |  9 +++++++++
 io_uring/uring_cmd.c          | 16 +++++++++++++++-
 3 files changed, 25 insertions(+), 2 deletions(-)

Comments

Jens Axboe Sept. 30, 2022, 1:26 a.m. UTC | #1

On 9/29/22 6:06 AM, Anuj Gupta wrote:
> diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
> index 6a6d69523d75..faefa9f6f259 100644
> --- a/io_uring/uring_cmd.c
> +++ b/io_uring/uring_cmd.c
> @@ -4,6 +4,7 @@
>  #include <linux/file.h>
>  #include <linux/io_uring.h>
>  #include <linux/security.h>
> +#include <linux/nospec.h>
>  
>  #include <uapi/linux/io_uring.h>
>  
> @@ -77,8 +78,21 @@ int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>  {
>  	struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
>  
> -	if (sqe->rw_flags || sqe->__pad1)
> +	if (sqe->__pad1)
>  		return -EINVAL;
> +
> +	ioucmd->flags = READ_ONCE(sqe->uring_cmd_flags);

After reading this and checking for IORING_URING_CMD_FIXED, this should
have a:

	if (iocmd->flags & ~IORING_URING_CMD_FIXED)
		return -EINVAL;

to ensure we can safely add more flags in the future. Apart from that,
this looks good.

Patch

diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
index 1dbf51115c30..e10c5cc81082 100644
--- a/include/linux/io_uring.h
+++ b/include/linux/io_uring.h
@@ -28,7 +28,7 @@  struct io_uring_cmd {
 		void *cookie;
 	};
 	u32		cmd_op;
-	u32		pad;
+	u32		flags;
 	u8		pdu[32]; /* available inline for free use */
 };
 
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 92f29d9505a6..ab7458033ee3 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -56,6 +56,7 @@  struct io_uring_sqe {
 		__u32		hardlink_flags;
 		__u32		xattr_flags;
 		__u32		msg_ring_flags;
+		__u32		uring_cmd_flags;
 	};
 	__u64	user_data;	/* data to be passed back at completion time */
 	/* pack this to avoid bogus arm OABI complaints */
@@ -219,6 +220,14 @@  enum io_uring_op {
 	IORING_OP_LAST,
 };
 
+/*
+ * sqe->uring_cmd_flags
+ * IORING_URING_CMD_FIXED	use registered buffer; pass thig flag
+ *				along with setting sqe->buf_index.
+ */
+#define IORING_URING_CMD_FIXED	(1U << 0)
+
+
 /*
  * sqe->fsync_flags
  */
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index 6a6d69523d75..faefa9f6f259 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -4,6 +4,7 @@ 
 #include <linux/file.h>
 #include <linux/io_uring.h>
 #include <linux/security.h>
+#include <linux/nospec.h>
 
 #include <uapi/linux/io_uring.h>
 
@@ -77,8 +78,21 @@  int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 	struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
 
-	if (sqe->rw_flags || sqe->__pad1)
+	if (sqe->__pad1)
 		return -EINVAL;
+
+	ioucmd->flags = READ_ONCE(sqe->uring_cmd_flags);
+	if (ioucmd->flags & IORING_URING_CMD_FIXED) {
+		struct io_ring_ctx *ctx = req->ctx;
+		u16 index;
+
+		req->buf_index = READ_ONCE(sqe->buf_index);
+		if (unlikely(req->buf_index >= ctx->nr_user_bufs))
+			return -EFAULT;
+		index = array_index_nospec(req->buf_index, ctx->nr_user_bufs);
+		req->imu = ctx->user_bufs[index];
+		io_req_set_rsrc_node(req, ctx, 0);
+	}
 	ioucmd->cmd = sqe->cmd;
 	ioucmd->cmd_op = READ_ONCE(sqe->cmd_op);
 	return 0;