On Thu, Feb 16, 2023 at 01:33:16PM +0100, Jan Kara wrote: > I'm a bit skeptical we can reasonably assess that (as much as I would love > to just not write these pages and be done with it) because a lot of > FOLL_LONGTERM users just pin passed userspace address range, then allow > userspace to manipulate it with other operations, and finally unpin it with > another call. Who knows whether shared pagecache pages are passed in and > what userspace is doing with them while they are pinned? True. So what other sensible thing could we do at a higher level? Treat MAP_SHARED buffers that are long term registered as MAP_PRIVATE while registered, and just do writeback using in-kernel O_DIRECT on fsync?
