[Linaro-mm-sig] Re: [PATCH v4 2/4] dmabuf: Implement copy_file_range callback for dmabuf direct I/O prep

On Tue, Jun 03, 2025 at 05:52:43PM +0800, wangtao wrote:

+static ssize_t dma_buf_rw_file(struct dma_buf *dmabuf, loff_t my_pos,

• struct file *file, loff_t pos, size_t count, bool is_write)

+{

• if (!dmabuf->ops->rw_file)

• return -EINVAL;
  

• if (my_pos >= dmabuf->size)

• count = 0;
  

• else

• count = min_t(size_t, count, dmabuf->size - my_pos);
  

• if (!count)

• return 0;
  

• return dmabuf->ops->rw_file(dmabuf, my_pos, file, pos, count, is_write);

So despite claiming in the cover letter that dmabufs can't support direct I/O you are just reimplementing it badly here using a side interface.