On Fri, Jan 18, 2019 at 9:45 AM Vlastimil Babka <vbabka@xxxxxxx> wrote: > > Or maybe we could resort to the 5.0-rc1 page table check (that is now being > reverted) but only in cases when we are not allowed the page cache residency > check? Or would that be needlessly complicated? I think it would be good fallback semantics, but I'm not sure it's worth it. Have you tried writing a patch for it? I don't think you'd want to do the check *when* you find a hole, so you'd have to do it upfront and then pass the cached data down with the private pointer (or have a separate "struct mm_walk" structure, perhaps? So I suspect we're better off with the patch we have. But if somebody *wants* to try to do that fancier patch, and it doesn't look horrendous, I think it might be the "quality" solution. Linus