On Tue, Jun 03, 2025 at 03:14:20PM +0200, Christian König wrote: > On 6/3/25 15:00, Christoph Hellwig wrote: > > This is a really weird interface. No one has yet to explain why dmabuf > > is so special that we can't support direct I/O to it when we can support > > it to otherwise exotic mappings like PCI P2P ones. > > With udmabuf you can do direct I/O, it's just inefficient to walk the > page tables for it when you already have an array of all the folios. Does it matter compared to the I/O in this case? Either way there has been talk (in case of networking implementations) that use a dmabuf as a first class container for lower level I/O. I'd much rather do that than adding odd side interfaces. I.e. have a version of splice that doesn't bother with the pipe, but instead just uses in-kernel direct I/O on one side and dmabuf-provided folios on the other.
