[RFC 05/13] io_uring: add flag and helper for fixed-buffer uring-cmd

[Kanchan Joshi <joshi.k@samsung.com>]

Add URING_CMD_FIXEDBUFS flag to use fixedbufs enabled passthrough.
Refactor the existing code and factor out helper that can be used for
passthrough with fixed-buffer. This is a prep patch.

Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Signed-off-by: Anuj Gupta <anuj20.g@samsung.com>
---
 fs/io_uring.c            | 20 ++++++++++++++------
 include/linux/io_uring.h | 10 ++++++++++
 2 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 1061b4cde4be..cc6735913c4b 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3125,12 +3125,10 @@ static void kiocb_done(struct io_kiocb *req, ssize_t ret,
 		}
 	}
 }
-
-static int __io_import_fixed(struct io_kiocb *req, int rw, struct iov_iter *iter,
-			     struct io_mapped_ubuf *imu)
+static int __io_import_fixed(u64 buf_addr, size_t len, int rw,
+			struct iov_iter *iter, struct io_mapped_ubuf *imu)
 {
-	size_t len = req->rw.len;
-	u64 buf_end, buf_addr = req->rw.addr;
+	u64 buf_end;
 	size_t offset;
 
 	if (unlikely(check_add_overflow(buf_addr, (u64)len, &buf_end)))
@@ -3199,8 +3197,18 @@ static int io_import_fixed(struct io_kiocb *req, int rw, struct iov_iter *iter)
 		imu = READ_ONCE(ctx->user_bufs[index]);
 		req->imu = imu;
 	}
-	return __io_import_fixed(req, rw, iter, imu);
+	return __io_import_fixed(req->rw.addr, req->rw.len, rw, iter, imu);
+}
+
+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_mapped_ubuf *imu = req->imu;
+
+	return __io_import_fixed(ubuf, len, rw, iter, imu);
 }
+EXPORT_SYMBOL_GPL(io_uring_cmd_import_fixed);
 
 static void io_ring_submit_unlock(struct io_ring_ctx *ctx, bool needs_lock)
 {
diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
index 5ab824ced147..07732bc850af 100644
--- a/include/linux/io_uring.h
+++ b/include/linux/io_uring.h
@@ -5,6 +5,9 @@
 #include <linux/sched.h>
 #include <linux/xarray.h>
 
+enum {
+	URING_CMD_FIXEDBUFS = (1 << 1),
+};
 /*
  * Note that the first member here must be a struct file, as the
  * io_uring command layout depends on that.
@@ -20,6 +23,8 @@ 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);
 void io_uring_cmd_done(struct io_uring_cmd *cmd, ssize_t ret);
 void io_uring_cmd_complete_in_task(struct io_uring_cmd *ioucmd,
 			void (*driver_cb)(struct io_uring_cmd *));
@@ -50,6 +55,11 @@ static inline void io_uring_cmd_complete_in_task(struct io_uring_cmd *ioucmd,
 			void (*driver_cb)(struct io_uring_cmd *))
 {
 }
+int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len,
+		int rw, struct iov_iter *iter, void *ioucmd)
+{
+	return -1;
+}
 static inline struct sock *io_uring_get_socket(struct file *file)
 {
 	return NULL;
-- 
2.25.1