On Fri, Nov 29, 2024 at 01:12:57PM +0100, David Hildenbrand wrote: > Well, I think we simply will want vm_insert_pages_prot() that stops treating > these things like folios :) . *likely* we'd want a distinct memdesc/type. > > We could start that work right now by making some user (iouring, > ring_buffer) set a new page->_type, and checking that in > vm_insert_pages_prot() + vm_normal_page(). If set, don't touch the refcount > and the mapcount. > > Because then, we can just make all the relevant drivers set the type, refuse > in vm_insert_pages_prot() anything that doesn't have the type set, and > refuse in vm_normal_page() any pages with this memdesc. > > Maybe we'd have to teach CoW to copy from such pages, maybe not. GUP of > these things will stop working, I hope that is not a problem. Well... perf-tool likes to call write() upon these pages in order to write out the data from the mmap() into a file.
