[RFC PATCH 4/6] io_uring: add helper for fixed-buffer uring-cmd

[Kanchan Joshi <joshi.k@xxxxxxxxxxx>]

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@xxxxxxxxxxx>
Signed-off-by: Anuj Gupta <anuj20.g@xxxxxxxxxxx>
---
 fs/io_uring.c            | 21 +++++++++++++++------
 include/linux/io_uring.h |  7 +++++++
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 3361056313a7..1f2263a78c8e 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2792,12 +2792,10 @@ static void kiocb_done(struct kiocb *kiocb, 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)))
@@ -2864,8 +2862,19 @@ 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(void *ubuf, unsigned long len,
+		int rw, struct iov_iter *iter, void *ioucmd)
+{
+	u64 buf_addr = (u64)ubuf;
+	struct io_kiocb *req = container_of(ioucmd, struct io_kiocb, uring_cmd);
+	struct io_mapped_ubuf *imu = req->imu;
+
+	return __io_import_fixed(buf_addr, 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 235d1603f97e..0bd8f611edb8 100644
--- a/include/linux/io_uring.h
+++ b/include/linux/io_uring.h
@@ -20,6 +20,8 @@ struct io_uring_cmd {
 };
 
 #if defined(CONFIG_IO_URING)
+int io_uring_cmd_import_fixed(void *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 *));
@@ -49,6 +51,11 @@ 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(void *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