On Wed 29-11-17 16:13:53, Rasmus Villemoes wrote: > On 2017-11-29 15:42, Michal Hocko wrote: [...] > >The flag is introduced as a completely > > new one rather than a MAP_FIXED extension because of the backward > > compatibility. We really want a never-clobber semantic even on older > > kernels which do not recognize the flag. Unfortunately mmap sucks wrt. > > flags evaluation because we do not EINVAL on unknown flags. On those > > kernels we would simply use the traditional hint based semantic so the > > caller can still get a different address (which sucks) but at least not > > silently corrupt an existing mapping. I do not see a good way around > > that. > > I think it would be nice if this rationale was in the 1/2 changelog, > along with the hint about what userspace that wants to be compatible > with old kernels will have to do (namely, check that it got what it > requested) - which I see you did put in the man page. OK, I've added there. -- Michal Hocko SUSE Labs
