[RFC PATCH 07/12] io_uring: support for using registered queue in uring-cmd

[Kanchan Joshi]

Add a new flag IORING_URING_CMD_DIRECT that user-space can spcifiy in SQE.
If queue is registered with the ring, this flag goes down to the provider
of ->uring_cmd. Provider may choose to do things differently or ignore
this flag.
Also export a helper that allows retrieving the identifier of the
registered queue.

Signed-off-by: Kanchan Joshi <joshi.k at samsung.com>
---
 include/linux/io_uring.h      |  6 ++++++
 include/uapi/linux/io_uring.h |  2 ++
 io_uring/uring_cmd.c          | 14 +++++++++++++-
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
index 35b9328ca335..bb6f900411e1 100644
--- a/include/linux/io_uring.h
+++ b/include/linux/io_uring.h
@@ -37,6 +37,7 @@ struct io_uring_cmd {
 };
 
 #if defined(CONFIG_IO_URING)
+int io_uring_cmd_import_qid(void *ioucmd);
 int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
 			      struct iov_iter *iter, void *ioucmd);
 void io_uring_cmd_done(struct io_uring_cmd *cmd, ssize_t ret, ssize_t res2,
@@ -67,6 +68,11 @@ static inline void io_uring_free(struct task_struct *tsk)
 		__io_uring_free(tsk);
 }
 #else
+static inline int io_uring_cmd_import_qid(void *ioucmd)
+{
+	return -EOPNOTSUPP;
+}
+
 static inline int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
 			      struct iov_iter *iter, void *ioucmd)
 {
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index a9d59bfd26f7..67fbcfd3f676 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -232,8 +232,10 @@ enum io_uring_op {
  * sqe->uring_cmd_flags
  * IORING_URING_CMD_FIXED	use registered buffer; pass this flag
  *				along with setting sqe->buf_index.
+ * IORING_URING_CMD_DIRECT	use registered queue for this cmd.
  */
 #define IORING_URING_CMD_FIXED	(1U << 0)
+#define IORING_URING_CMD_DIRECT	(1U << 1)
 
 
 /*
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index 5113c9a48583..2a543b490045 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -89,9 +89,12 @@ int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		return -EINVAL;
 
 	ioucmd->flags = READ_ONCE(sqe->uring_cmd_flags);
-	if (ioucmd->flags & ~IORING_URING_CMD_FIXED)
+	if (ioucmd->flags & ~(IORING_URING_CMD_FIXED | IORING_URING_CMD_DIRECT))
 		return -EINVAL;
 
+	if (ioucmd->flags & IORING_URING_CMD_DIRECT &&
+			req->ctx->dev_qid == -EINVAL)
+		return -EINVAL;
 	if (ioucmd->flags & IORING_URING_CMD_FIXED) {
 		struct io_ring_ctx *ctx = req->ctx;
 		u16 index;
@@ -162,3 +165,12 @@ int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
 	return io_import_fixed(rw, iter, req->imu, ubuf, len);
 }
 EXPORT_SYMBOL_GPL(io_uring_cmd_import_fixed);
+
+int io_uring_cmd_import_qid(void *ioucmd)
+{
+	struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);
+	struct io_ring_ctx *ctx = req->ctx;
+
+	return ctx->dev_qid;
+}
+EXPORT_SYMBOL_GPL(io_uring_cmd_import_qid);
-- 
2.25.1