On Tue, Oct 19, 2021 at 12:11:35PM -0400, Kent Overstreet wrote: > I have no idea if this approach works for network pool pages or how those would > be used, I haven't gotten that far - if someone can chime in about those that Generally the driver goal is to create a shared memory buffer between kernel and user space. The broadly two common patterns are to have userspace call mmap() and the kernel side returns the kernel pages from there - getting them from some kernel allocator. Or, userspace allocates the buffer and the kernel driver does pin_user_pages() to import them to its address space. I think it is quite feasible to provide some simple library API to manage the shared buffer through mmap approach, and if that library wants to allocate inodes, folios and what not it should be possible. It would help this idea to see Christoph's cleanup series go forward: https://lore.kernel.org/all/20200508153634.249933-1-hch@xxxxxx/ As it makes it alot easier for drivers to get inodes in the first place. > would be great. But, the end goal I'm envisioning is a world where _only_ bog > standard file & anonymous pages are mapped to userspace - then _mapcount can be > deleted from struct page and only needs to live in struct folio. There is a lot of work in the past years on ZONE_DEVICE pages into userspace. Today FSDAX is kind of a mashup of a file and device page, but other stuff is less obvious, especially DEVICE_COHERENT. Jason
