Add DMA_BUF_IOCTL_RW_FILE to save/restore data to/from a dma-buf.
For large dmabuf operations (model loading, real-time data capture,
task snapshots), Direct I/O with zero-copy boosts performance
by avoiding file cache/memory copies, cuts CPU/power use. On UFS 4.0
(@4GB/s): dmabuf Direct I/O hits 3776MB/s read speed.
Signed-off-by: wangtao <tao.wang...@honor.com>
---
drivers/dma-buf/dma-buf.c | 8 ++++++++
include/linux/dma-buf.h | 15 +++++++++++++++
include/uapi/linux/dma-buf.h | 28 ++++++++++++++++++++++++++++
3 files changed, 51 insertions(+)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 5baa83b85515..95d8b0158ffd 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -460,6 +460,7 @@ static long dma_buf_ioctl(struct file *file,
struct dma_buf *dmabuf;
struct dma_buf_sync sync;
enum dma_data_direction direction;
+ struct dma_buf_rw_file kfile;
int ret;
dmabuf = file->private_data;
@@ -504,6 +505,13 @@ static long dma_buf_ioctl(struct file *file,
return dma_buf_import_sync_file(dmabuf, (const void __user
*)arg);
#endif
+ case DMA_BUF_IOCTL_RW_FILE:
+ if (copy_from_user(&kfile, (void __user *) arg, sizeof(kfile)))
+ return -EFAULT;
+ if (!dmabuf->ops->rw_file)
+ return -EINVAL;
+ return dmabuf->ops->rw_file(dmabuf, &kfile);
+
default:
return -ENOTTY;
}
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index 36216d28d8bd..6d2e6eae0611 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -22,6 +22,7 @@
#include <linux/fs.h>
#include <linux/dma-fence.h>
#include <linux/wait.h>
+#include <uapi/linux/dma-buf.h>
struct device;
struct dma_buf;
@@ -285,6 +286,20 @@ struct dma_buf_ops {
int (*vmap)(struct dma_buf *dmabuf, struct iosys_map *map);
void (*vunmap)(struct dma_buf *dmabuf, struct iosys_map *map);
+
+ /**
+ * @rw_file:
+ *
+ * If an Exporter needs to support Direct I/O file operations, it can
+ * implement this optional callback. The exporter must verify that no
+ * other objects hold the sg_table, ensure exclusive access to the
+ * dmabuf's sg_table, and only then proceed with the I/O operation.
+ *
+ * Returns:
+ *
+ * 0 on success or a negative error code on failure.
+ */
+ int (*rw_file)(struct dma_buf *dmabuf, struct dma_buf_rw_file *file);
};
/**
diff --git a/include/uapi/linux/dma-buf.h b/include/uapi/linux/dma-buf.h
index 5a6fda66d9ad..9b33279fef00 100644
--- a/include/uapi/linux/dma-buf.h
+++ b/include/uapi/linux/dma-buf.h
@@ -167,6 +167,28 @@ struct dma_buf_import_sync_file {
__s32 fd;
};
+/**
+ * struct dma_buf_rw_file - read/write file associated with a dma-buf
+ *
+ * Userspace can performs a DMA_BUF_IOCTL_BACK to save data from a dma-buf or
+ * restore data to a dma-buf.
+ */
+struct dma_buf_rw_file {
+ /** @flags: Flags indicating read/write for this dma-buf. */
+ __u32 flags;
+ /** @fd: File descriptor of the file associated with this dma-buf. */
+ __s32 fd;
+ /** @file_offset: Offset within the file where this dma-buf starts.
+ *
+ * Offset and Length must be page-aligned for direct I/O.
+ */
+ __u64 file_offset;
+ /** @buf_offset: Offset within this dma-buf where the read/write
starts. */
+ __u64 buf_offset;
+ /** @buf_len: Length of this dma-buf read/write. */
+ __u64 buf_len;
+};
+
#define DMA_BUF_BASE 'b'
#define DMA_BUF_IOCTL_SYNC _IOW(DMA_BUF_BASE, 0, struct dma_buf_sync)
@@ -179,4 +201,10 @@ struct dma_buf_import_sync_file {
#define DMA_BUF_IOCTL_EXPORT_SYNC_FILE _IOWR(DMA_BUF_BASE, 2, struct
dma_buf_export_sync_file)
#define DMA_BUF_IOCTL_IMPORT_SYNC_FILE _IOW(DMA_BUF_BASE, 3, struct
dma_buf_import_sync_file)
+#define DMA_BUF_RW_FLAGS_OP_MASK (0xFF << 0)
+#define DMA_BUF_RW_FLAGS_READ (1 << 0) /* Restore dma-buf data */
+#define DMA_BUF_RW_FLAGS_WRITE (2 << 0) /* Save dma-buf data */
+#define DMA_BUF_RW_FLAGS_DIRECT (1u << 31) /* Direct read/write file */
+#define DMA_BUF_IOCTL_RW_FILE _IOW(DMA_BUF_BASE, 4, struct dma_buf_rw_file)
+
#endif
--
2.17.1
