[PATCH 3/5] io_uring: add data to dma-buf convertion helpers

[Pavel Begunkov]

struct io_buf_dma is stored as void * in registered buffers, and it's
casted in multiple places. It's inconvenient as void* casts can't be
type checked, so wrap all of them into helpers and keep casting
centralised. No functional changes.

Fixes: 62e4bf5b25d44 ("io_uring/rsrc: add dmabuf backed registered buffers")
Signed-off-by: Pavel Begunkov <asml.sile...@gmail.com>
---
 io_uring/dma-buf.c |  2 +-
 io_uring/dma-buf.h | 14 ++++++++++++--
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/io_uring/dma-buf.c b/io_uring/dma-buf.c
index 132e3d0d7023..6f1d21c0f558 100644
--- a/io_uring/dma-buf.c
+++ b/io_uring/dma-buf.c
@@ -2,7 +2,7 @@
 
 static inline void io_release_dmabuf(void *priv)
 {
-       struct io_buf_dma *bd = priv;
+       struct io_buf_dma *bd = io_priv_to_dmabuf(priv);
 
        fput(bd->target_file);
        dma_buf_io_ctx_release(bd->ctx);
diff --git a/io_uring/dma-buf.h b/io_uring/dma-buf.h
index 534c06b6879f..a97412ebbb3f 100644
--- a/io_uring/dma-buf.h
+++ b/io_uring/dma-buf.h
@@ -12,6 +12,16 @@ struct io_buf_dma {
        struct file                     *target_file;
 };
 
+static inline struct io_buf_dma *io_priv_to_dmabuf(void *data)
+{
+       return data;
+}
+
+static inline struct io_buf_dma *io_buf_to_dmabuf(struct io_mapped_ubuf *imu)
+{
+       return io_priv_to_dmabuf(imu->priv);
+}
+
 int __io_register_dmabuf(struct io_ring_ctx *ctx,
                        struct io_uring_regbuf_desc *desc,
                        struct io_mapped_ubuf *imu);
@@ -39,7 +49,7 @@ static inline int io_attach_dmabuf_map(struct io_kiocb *req,
        if (!IS_ENABLED(CONFIG_DMA_SHARED_BUFFER))
                return -EOPNOTSUPP;
 
-       bd = req->buf_node->buf->priv;
+       bd = io_buf_to_dmabuf(req->buf_node->buf);
        map = dma_buf_io_get_map(bd->ctx, nowait);
        if (unlikely(IS_ERR(map)))
                return PTR_ERR(map);
@@ -53,7 +63,7 @@ static inline int io_import_dmabuf_map(struct io_kiocb *req,
                                struct io_mapped_ubuf *imu,
                                size_t len, size_t offset)
 {
-       struct io_buf_dma *bd = imu->priv;
+       struct io_buf_dma *bd = io_buf_to_dmabuf(imu);
 
        if (!IS_ENABLED(CONFIG_DMA_SHARED_BUFFER))
                return -EOPNOTSUPP;
-- 
2.54.0