[PATCH 07/17] io_uring: add support for uring_cmd with fixed-buffer

[Kanchan Joshi <joshi.k@xxxxxxxxxxx>]

Add IORING_OP_URING_CMD_FIXED opcode that enables performing the
operation with previously registered buffers.

Signed-off-by: Kanchan Joshi <joshi.k@xxxxxxxxxxx>
Signed-off-by: Anuj Gupta <anuj20.g@xxxxxxxxxxx>
---
 fs/io_uring.c                 | 29 ++++++++++++++++++++++++++++-
 include/linux/io_uring.h      |  1 +
 include/uapi/linux/io_uring.h |  1 +
 3 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index ead0cbae8416..6a1dcea0f538 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1107,6 +1107,9 @@ static const struct io_op_def io_op_defs[] = {
 	[IORING_OP_URING_CMD] = {
 		.needs_file		= 1,
 	},
+	[IORING_OP_URING_CMD_FIXED] = {
+		.needs_file		= 1,
+	},
 };
 
 /* requests with any of those set should undergo io_disarm_next() */
@@ -4148,16 +4151,25 @@ EXPORT_SYMBOL_GPL(io_uring_cmd_done);
 static int io_uring_cmd_prep(struct io_kiocb *req,
 			     const struct io_uring_sqe *sqe)
 {
+	struct io_ring_ctx *ctx = req->ctx;
 	struct io_uring_cmd *ioucmd = &req->uring_cmd;
 
 	if (!req->file->f_op->async_cmd || !(req->ctx->flags & IORING_SETUP_SQE128))
 		return -EOPNOTSUPP;
 	if (req->ctx->flags & IORING_SETUP_IOPOLL)
 		return -EOPNOTSUPP;
+	if (req->opcode == IORING_OP_URING_CMD_FIXED) {
+		req->imu = NULL;
+		io_req_set_rsrc_node(req, ctx);
+		req->buf_index = READ_ONCE(sqe->buf_index);
+		ioucmd->flags = IO_URING_F_UCMD_FIXEDBUFS;
+	} else {
+		ioucmd->flags = 0;
+	}
+
 	ioucmd->cmd = (void *) &sqe->cmd;
 	ioucmd->cmd_op = READ_ONCE(sqe->cmd_op);
 	ioucmd->cmd_len = READ_ONCE(sqe->cmd_len);
-	ioucmd->flags = 0;
 	return 0;
 }
 
@@ -4167,6 +4179,19 @@ static int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags)
 	int ret;
 	struct io_uring_cmd *ioucmd = &req->uring_cmd;
 
+	if (req->opcode == IORING_OP_URING_CMD_FIXED) {
+		u32 index, buf_index = req->buf_index;
+		struct io_ring_ctx *ctx = req->ctx;
+		struct io_mapped_ubuf *imu = req->imu;
+
+		if (likely(!imu)) {
+			if (unlikely(buf_index >= ctx->nr_user_bufs))
+				return -EFAULT;
+			index = array_index_nospec(buf_index, ctx->nr_user_bufs);
+			imu = READ_ONCE(ctx->user_bufs[index]);
+			req->imu = imu;
+		}
+	}
 	ioucmd->flags |= issue_flags;
 	ret = file->f_op->async_cmd(ioucmd);
 	/* queued async, consumer will call io_uring_cmd_done() when complete */
@@ -6656,6 +6681,7 @@ static int io_req_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	case IORING_OP_LINKAT:
 		return io_linkat_prep(req, sqe);
 	case IORING_OP_URING_CMD:
+	case IORING_OP_URING_CMD_FIXED:
 		return io_uring_cmd_prep(req, sqe);
 	}
 
@@ -6941,6 +6967,7 @@ static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
 		ret = io_linkat(req, issue_flags);
 		break;
 	case IORING_OP_URING_CMD:
+	case IORING_OP_URING_CMD_FIXED:
 		ret = io_uring_cmd(req, issue_flags);
 		break;
 	default:
diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
index 1888a5ea7dbe..abad6175739e 100644
--- a/include/linux/io_uring.h
+++ b/include/linux/io_uring.h
@@ -8,6 +8,7 @@
 enum io_uring_cmd_flags {
 	IO_URING_F_COMPLETE_DEFER	= 1,
 	IO_URING_F_UNLOCKED		= 2,
+	IO_URING_F_UCMD_FIXEDBUFS	= 4,
 	/* int's last bit, sign checks are usually faster than a bit test */
 	IO_URING_F_NONBLOCK		= INT_MIN,
 };
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 9bf1d6c0ed7f..ee84be4b6be8 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -155,6 +155,7 @@ enum {
 	IORING_OP_SYMLINKAT,
 	IORING_OP_LINKAT,
 	IORING_OP_URING_CMD,
+	IORING_OP_URING_CMD_FIXED,
 
 	/* this goes last, obviously */
 	IORING_OP_LAST,
-- 
2.25.1