On Wed, Apr 19, 2023 at 07:45:06PM +0100, Lorenzo Stoakes wrote: > For example, imagine if a user (yes it'd be weird) mlock'd some pages in a > buffer and not others, then we'd break their use case. Also (perhaps?) more > feasibly, a user might mix hugetlb and anon pages. So I think that'd be too > restrictive here. Yeah, I agree we should not add a broad single-vma restriction to GUP. It turns any split of a VMA into a potentially uABI breaking change and we just don't need that headache in the mm.. > I do like the idea of a FOLL_SINGLE_VMA for other use cases though, the > majority of which want one and one page only. Perhaps worth taking the > helper added in this series (get_user_page_vma_remote() from [1]) and > replacing it with an a full GUP function which has an interface explicitly > for this common single page/vma case. Like I showed in another thread a function signature that can only do one page and also returns the VMA would force it to be used properly and we don't need a FOLL flag. Jason
