On 16 Nov 2022, at 0:12, Christoph Hellwig wrote: > On Mon, Nov 07, 2022 at 09:05:11PM -0800, Jonathan Lemon wrote: >> The network stack passes up pages, which must be mapped to >> zctap device buffers in order to get the reference count and >> other items. Mark the page as private, and use the page_private >> field to record the lookup and ownership information. > > Who coordinate ownership of page_private here? What other parts > of the kernel could touch these pages? This may be an issue. The driver, network stack, and application all utilize the pages, which have been pinned by io_uring. If the pages are passed to another subsystem which wants to use the private area for its own purposes, there will be a conflict. There doesn’t seem to be a good way to maintain long term information in the current page structure. A resolution for this would be using an external lookup indexed by the page, or changing the information passed up in the skb. — Jonathan
