On Sun, May 28, 2023 at 04:13:44PM +0100, Lorenzo Stoakes wrote: > On Sat, May 27, 2023 at 06:52:01AM -0300, Jason Gunthorpe wrote: > > On Sat, May 20, 2023 at 10:12:40AM +0100, Lorenzo Stoakes wrote: > > > > No, this returning 0 on failure is a foot gun. Failing to pin a single > > > > page is always an error, the only question is what sub reason caused > > > > the error to happen. There is no third case where it is not an error. > > > > > > The uprobe path thinks otherwise, but maybe the answer is that we just need > > > to -EFAULT on missing VMA and -EPERM on invalid flags. > > > > I think uprobe is just broken to think there is a third outcome. Let's > > just fix it instead of trying to pretend it makes sense. > > Sure, will take a look at that if I get a chance. We can at the very least > adjust get_user_page_vma_remote() with this fixed. > > Do you feel that a partially successful pinning for other GUP callers > should equally be treated as an error (and pages unpinned -> return error > code)? In that instance we'd need to audit things somewhat. That seems more deeply ingrained at least, I'm not as keen to change it as to get rid of the 0 return result. Jason
