[PATCH for-next v2 2/4] io_uring: introduce fixed buffer support for io_uring_cmd

[Kanchan Joshi]

From: Anuj Gupta <anuj20.g at samsung.com>

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 <anuj20.g at samsung.com>
Signed-off-by: Kanchan Joshi <joshi.k at samsung.com>
---
 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) {
 			struct io_uring_cmd *ioucmd = (struct io_uring_cmd *)rw;
 
 			ret = req->file->f_op->uring_cmd_iopoll(ioucmd);
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index ff65cc8ab6cc..9383150b2949 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -3,11 +3,13 @@
 #include <linux/errno.h>
 #include <linux/file.h>
 #include <linux/io_uring.h>
+#include <linux/nospec.h>
 
 #include <uapi/linux/io_uring.h>
 
 #include "io_uring.h"
 #include "uring_cmd.h"
+#include "rsrc.h"
 
 static void io_uring_cmd_work(struct io_kiocb *req, bool *locked)
 {
@@ -74,6 +76,18 @@ int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 
 	if (sqe->rw_flags || sqe->__pad1)
 		return -EINVAL;
+
+	req->buf_index = READ_ONCE(sqe->buf_index);
+	if (req->opcode == IORING_OP_URING_CMD_FIXED) {
+		struct io_ring_ctx *ctx = req->ctx;
+		u16 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;
@@ -98,6 +112,8 @@ int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags)
 		req->iopoll_completed = 0;
 		WRITE_ONCE(ioucmd->cookie, NULL);
 	}
+	if (req->opcode == IORING_OP_URING_CMD_FIXED)
+		issue_flags |= IO_URING_F_FIXEDBUFS;
 
 	if (req_has_async_data(req))
 		ioucmd->cmd = req->async_data;
@@ -125,7 +141,7 @@ int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags)
 int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len,
 		int rw, struct iov_iter *iter, void *ioucmd)
 {
-	struct io_kiocb *req = container_of(ioucmd, struct io_kiocb, uring_cmd);
+	struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);
 	struct io_mapped_ubuf *imu = req->imu;
 
 	return io_import_fixed(rw, iter, imu, ubuf, len);
-- 
2.25.1