On Thu, Jul 18, 2024 at 09:51:39AM +0800, Huan Yang wrote:

Yes, actually, if dma-buf want's to copy_file_range from a file, it need change something in vfs_copy_file_range:

No, it doesn't. copy_file_range is specifically designed to copy inside a single file system as already mentioned. The generic offload for copying between arbitrary FDs is splice and the sendfile convenience wrapper around it