On Fri, Jul 11, 2025, Ira Weiny wrote: > Michael Roth wrote: > > For in-place conversion: the idea is that userspace will convert > > private->shared to update in-place, then immediately convert back > > shared->private; > > Why convert from private to shared and back to private? Userspace which > knows about mmap and supports it should create shared pages, mmap, write > data, then convert to private. Dunno if there's a strong usecase for converting to shared *and* populating the data, but I also don't know that it's worth going out of our way to prevent such behavior, at least not without a strong reason to do so. E.g. if it allowed for a cleaner implementation or better semantics, then by all means. But I don't think that's true here? Though I haven't thought hard about this, so don't quote me on that. :-) > Old userspace will create private and pass in a source pointer for the > initial data as it does today. > > Internally, the post_populate() callback only needs to know if the data is > in place or coming from somewhere else (ie src != NULL). I think there will be a third option: data needs to be zeroed, i.e. the !src && !PRESERVED case.
