[PATCH for-next v8 2/5] io_uring: introduce fixed buffer support for io_uring_cmd

Kanchan Joshi
2022-09-23T09:40:32Z

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

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 <anuj20.g@samsung.com>
Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
---
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(-)

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;
--
2.25.1