Hey, I've just got pinged by Lennart who discovered that you can get your system into an unuseable state by writing something that exceeds a s64 into /proc/sys/fs/file-max. Say,
echo 20000000000000000000 > /proc/sys/fs/file-max which will trigger an overflow and percpu_counter_read_positive() will return 0 and cat /proc/sys/fs/file-max will return 0. That effectively means you write that number and it succeeds and all is well and a few seconds/minutes later your system just dies or gets into an unuseable state pretty quickly I wonder if we shouldn't accept overflows or - if we have no way in this codepath to detect them - set it to some pre-defined hard-coded value. Or maybe this is even a known issue and by design but before I work on a patch here I just wanted to check. Christian
