On Mon, Jan 11, 2021 at 02:18:13PM -0800, Linus Torvalds wrote: > The whole "optimistic page references throigh page cache" etc are > complete non-issues, because the whole point is that we already know > it's not a page cache page. There is simply no other way to reach that > page than through GUP. The thing about the speculative page cache references is that they can temporarily bump a refcount on a page which _used_ to be in the page cache and has now been reallocated as some other kind of page. Now, this is obviously rare, so if it's only a performance question, it'll be fine. If there's a correctness issue with copying pages that would otherwise not have been copied, then it's a problem.
