On Tue, Jun 20, 2023 at 05:28:28PM +0200, David Hildenbrand wrote: > On 20.06.23 01:10, Peter Xu wrote: > > follow_page() doesn't use FOLL_PIN, meanwhile hugetlb seems to not be the > > target of FOLL_WRITE either. However add the checks. > > > > Namely, either the need to CoW due to missing write bit, or proper CoR on > > !AnonExclusive pages over R/O pins to reject the follow page. That brings > > this function closer to follow_hugetlb_page(). > > > > So we don't care before, and also for now. But we'll care if we switch > > over slow-gup to use hugetlb_follow_page_mask(). We'll also care when to > > return -EMLINK properly, as that's the gup internal api to mean "we should > > do CoR". Not really needed for follow page path, though. > > > > When at it, switching the try_grab_page() to use WARN_ON_ONCE(), to be > > clear that it just should never fail. > > Oh, and does this comment really belong into this patch or am I confused? Ah yeh, thanks for spotting. I used to have it in v1 but I kept the old failure path here to partly address Lorenzo's worry; but then I forgot to add the WARN_ON_ONCE back to guard. I'll remember to add that in v3. -- Peter Xu
