[V8,6/7] io_uring/uring_cmd: support leasing device kernel buffer to io_uring

Commit Message

Ming Lei Oct. 25, 2024, 12:22 p.m. UTC

Add API of io_uring_cmd_lease_kbuf() for driver to lease its kernel
buffer to io_uring.

The leased buffer can only be consumed by io_uring OPs in group wide,
and the uring_cmd has to be one group leader.

This way can support generic device zero copy over device buffer in
userspace:

- create one sqe group
- lease one device buffer to io_uring by the group leader of uring_cmd
- io_uring member OPs consume this kernel buffer by passing IOSQE_IO_DRAIN
  which isn't used for group member, and mapped to GROUP_KBUF.
- the kernel buffer is returned back after all member OPs are completed

Signed-off-by: Ming Lei <[e-mail]>
---
 include/linux/io_uring/cmd.h |  7 +++++++
 io_uring/uring_cmd.c         | 13 +++++++++++++
 2 files changed, 20 insertions(+)

Patch

diff --git a/include/linux/io_uring/cmd.h b/include/linux/io_uring/cmd.h
index c189d36ad55e..bdf7abfa0d8a 100644
--- a/include/linux/io_uring/cmd.h
+++ b/include/linux/io_uring/cmd.h
@@ -60,6 +60,8 @@  void io_uring_cmd_mark_cancelable(struct io_uring_cmd *cmd,
 /* Execute the request from a blocking context */
 void io_uring_cmd_issue_blocking(struct io_uring_cmd *ioucmd);
 
+int io_uring_cmd_lease_kbuf(struct io_uring_cmd *ioucmd,
+		const struct io_uring_kernel_buf *grp_kbuf);
 #else
 static inline int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
 			      struct iov_iter *iter, void *ioucmd)
@@ -82,6 +84,11 @@  static inline void io_uring_cmd_mark_cancelable(struct io_uring_cmd *cmd,
 static inline void io_uring_cmd_issue_blocking(struct io_uring_cmd *ioucmd)
 {
 }
+static inline int io_uring_cmd_lease_kbuf(struct io_uring_cmd *ioucmd,
+		const struct io_uring_kernel_buf *grp_kbuf)
+{
+	return -EOPNOTSUPP;
+}
 #endif
 
 /*
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index 6994f60d7ec7..2c9c2c60c6cd 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -15,6 +15,7 @@ 
 #include "alloc_cache.h"
 #include "rsrc.h"
 #include "uring_cmd.h"
+#include "kbuf.h"
 
 static struct uring_cache *io_uring_async_get(struct io_kiocb *req)
 {
@@ -175,6 +176,18 @@  void io_uring_cmd_done(struct io_uring_cmd *ioucmd, ssize_t ret, ssize_t res2,
 }
 EXPORT_SYMBOL_GPL(io_uring_cmd_done);
 
+int io_uring_cmd_lease_kbuf(struct io_uring_cmd *ioucmd,
+		const struct io_uring_kernel_buf *grp_kbuf)
+{
+	struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);
+
+	if (unlikely(ioucmd->flags & IORING_URING_CMD_FIXED))
+		return -EINVAL;
+
+	return io_lease_group_kbuf(req, grp_kbuf);
+}
+EXPORT_SYMBOL_GPL(io_uring_cmd_lease_kbuf);
+
 static int io_uring_cmd_prep_setup(struct io_kiocb *req,
 				   const struct io_uring_sqe *sqe)
 {