Hi, I'm trying to remove the current page handling in binder and switch to using ->fault() and other mm/ infrastructure. See, we currently allocate and insert pages manually into vmas, so dropping this boilerplate code seems like a great idea to me. Before starting on this though, I could use some pointers on some of the implementation details. In binder the messages are not buffered. What happens is that a server task mmaps a region and then allows clients to write their user data directly into this _remote_ vma. This is currently achieved by caching pointers to every page allocated in the server's region. Instead of caching page pointers, I believe binder could make use of get_user_pages_remote() and trigger a page fault as needed. Basically, implement something similar to access_remote_vm() but that instead does a copy_from_user(). However, I don't see many in-tree users of these routines, so I wonder if I'm overlooking something in this approach? One more reason for the page caching in binder is being able to free pages from the shrinker's callback. Unused pages are added to an LRU list and we manually zap/free them when they are reclaimed. It is not evident to me how can binder mark a range within the vma region as reclaimable? Any pointers are appreciated! -- Carlos Llamas
