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? -- Cheers, David / dhildenb
