From: Anuj Gupta <redacted>

Add IORING_OP_URING_CMD_FIXED opcode that enables 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 <redacted>
Signed-off-by: Kanchan Joshi <redacted>
---
  include/linux/io_uring.h      |  5 ++++-
  include/uapi/linux/io_uring.h |  1 +
  io_uring/opdef.c              | 10 ++++++++++
  io_uring/rw.c                 |  3 ++-
  io_uring/uring_cmd.c          | 18 +++++++++++++++++-
  5 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
index 60aba10468fc..40961d7c3827 100644
--- a/include/linux/io_uring.h
+++ b/include/linux/io_uring.h

@@ -5,6 +5,8 @@
  #include <linux/sched.h>
  #include <linux/xarray.h>
  
+#include<uapi/linux/io_uring.h>
+
  enum io_uring_cmd_flags {
  	IO_URING_F_COMPLETE_DEFER	= 1,
  	IO_URING_F_UNLOCKED		= 2,

@@ -15,6 +17,7 @@ enum io_uring_cmd_flags {
  	IO_URING_F_SQE128		= 4,
  	IO_URING_F_CQE32		= 8,
  	IO_URING_F_IOPOLL		= 16,
+	IO_URING_F_FIXEDBUFS		= 32,
  };
  
  struct io_uring_cmd {

@@ -33,7 +36,7 @@ struct io_uring_cmd {
  
  #if defined(CONFIG_IO_URING)
  int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
-		struct iov_iter *iter, void *ioucmd)
+		struct iov_iter *iter, void *ioucmd);

  void io_uring_cmd_done(struct io_uring_cmd *cmd, ssize_t ret, ssize_t res2);
  void io_uring_cmd_complete_in_task(struct io_uring_cmd *ioucmd,
  			void (*task_work_cb)(struct io_uring_cmd *));

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 1463cfecb56b..80ea35d1ed5c 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h

@@ -203,6 +203,7 @@ enum io_uring_op {
  	IORING_OP_SOCKET,
  	IORING_OP_URING_CMD,
  	IORING_OP_SENDZC_NOTIF,
+	IORING_OP_URING_CMD_FIXED,

  	/* this goes last, obviously */
  	IORING_OP_LAST,

diff --git a/io_uring/opdef.c b/io_uring/opdef.c
index 9a0df19306fe..7d5731b84c92 100644
--- a/io_uring/opdef.c
+++ b/io_uring/opdef.c

@@ -472,6 +472,16 @@ const struct io_op_def io_op_defs[] = {
  		.issue			= io_uring_cmd,
  		.prep_async		= io_uring_cmd_prep_async,
  	},
+	[IORING_OP_URING_CMD_FIXED] = {
+		.needs_file		= 1,
+		.plug			= 1,
+		.name			= "URING_CMD_FIXED",
+		.iopoll			= 1,
+		.async_size		= uring_cmd_pdu_size(1),
+		.prep			= io_uring_cmd_prep,
+		.issue			= io_uring_cmd,
+		.prep_async		= io_uring_cmd_prep_async,
+	},
  	[IORING_OP_SENDZC_NOTIF] = {
  		.name			= "SENDZC_NOTIF",
  		.needs_file		= 1,

diff --git a/io_uring/rw.c b/io_uring/rw.c
index 1a4fb8a44b9a..3c7b94bffa62 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c

@@ -1005,7 +1005,8 @@ int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin)
  		if (READ_ONCE(req->iopoll_completed))
  			break;
  
-		if (req->opcode == IORING_OP_URING_CMD) {
+		if (req->opcode == IORING_OP_URING_CMD ||
+				req->opcode == IORING_OP_URING_CMD_FIXED) {