On Fri, Jun 13, 2025 at 09:33:55AM +0000, wangtao wrote:

...

On Mon, Jun 09, 2025 at 09:32:20AM +0000, wangtao wrote:

...

Are you suggesting adding an ITER_DMABUF type to iov_iter,

Yes.

May I clarify: Do all disk operations require data to pass through memory (reading into memory or writing from memory)? In the block layer, the bio structure uses bio_iov_iter_get_pages to convert iter_type objects into memory-backed bio_vec representations. However, some dmabufs are not memory-based, making page-to-bio_vec conversion impossible. This suggests adding a callback function in dma_buf_ops to handle dmabuf- to-bio_vec conversion.

bios do support PCI P2P tranfers. This could be fairly easily extended to other peer to peer transfers if we manage to come up with a coherent model for them. No need for a callback.