Hi John, Thanks for your comments and sorry for the delayed response, I was off the last few days. On 2024-06-14 20:40, John Hubbard wrote: > s/folio_fast_pin_allowed/gup_fast_folio_allowed/ ? Nice catch! That function got renamed from the original work we did on this series. > This comment is very difficult, because it states that one cannot > do something, right before explicitly enable something else. And the > reader is given little help on connecting the two. > > And there are several subtypes of ZONE_DEVICE. Is it really true that > none of them can be mapped to user space? For p2p BAR1 mappings, those > actually go to user space, yes? Confused, need help. :) This is a fair point, I had only looked at p2p but I can't say anything about the other subtypes of ZONE_DEVICE. For p2p, yes, they will go to userspace, however folio->mapping was NULL for those cases. And hence fast path would reject it. In any case, I think we could drop this patch for now and revisit when/if required, the regular gup path was not measurably slower. Thanks, Martin
