is this maybe different under the HWE kernel (I’m running 16.04 xenial’s 4.10.0-27-generic HWE kernel)? There appears to be a regression that @jdstrand and I have been working to diagnose with this kernel and accessing /dev/zero (File_mmap of /dev/zero is currently blocked) so it surely isn’t inconceivable that there are other problems, such as maybe this one.