On Mon, May 12, 2025 at 03:51:30PM +0100, David Howells wrote: > I'm looking at how to make sendmsg() handle page pinning - and also working > towards supporting the page refcount eventually being removed and only being > available with certain memory types. Yes, that would be great. > The question is what should happen here to a memory span for which the network > layer or pipe driver is not allowed to take reference, but rather must call a > destructor? Particularly if, say, it's just a small part of a larger span. What is a "span" in this context? In general splice unlike direct I/O relies on page reference counts inside the splice machinery. But that is configurable through the pipe_buf_operations. So if you want something to be handled by splice that does not use simple page refcounts you need special pipe_buf_operations for it. And you'd better have a really good use case for this to be worthwhile. > And then there's vmsplice(). The same goes for vmsplice() to AF_UNIX or to a > pipe. That should also pin memory. It may also be possible to vmsplice a > pinned page into the target process's VM or a page from a memory span with > some other type of destruction. I don't suppose we can deprecate vmsplice()? You'll need a longterm pin for vmsplice. I'd love to deprecate it, but I doubt it's going to go away any time soon if ever.
