On Wed 08-04-20 09:20:00, Linus Torvalds wrote: > On Wed, Apr 8, 2020 at 8:59 AM Peter Xu <peterx@xxxxxxxxxx> wrote: > > > > __get_user_pages_locked() will return 0 instead of -EINTR after commit > > 4426e945df588 which added extra code to allow gup detect fatal signal > > faster. Restore that behavior. > > I've applied this, but it's worth noting that > __get_user_pages_locked() can still return 0 in other situations. > > I realize that "I got zero pages" is a valid return value, but I do > wonder if we should make the rule be that a zero return value isn't > possible (return -EAGAIN or whatever if you doin't have the > EFAULT/EINTR conditions). > > So that you'd always get either an error, or a successful number of pages. > > The only case where __get_user_pages_locked() might return zero is if > you pass in a zero 'nr_pages', although I suspect even for that case > returning -EINVAL might be a better option. Yeah, that makes sense to me. And get_user_pages_locked documentation would benefit from an actual documentation as well. What we have right now is more suited to the lower level (__get_user_pages_locked) and have a high level user oriented documentation. -- Michal Hocko SUSE Labs
