Ah, yes, the (2**64 - 1) + 1 problem. The fact max allowed remaining is (2**64 - 2) is perhaps surprising... should we clamp? or warn? userspace has: if (cb->entry->id == O_REMAIN) info->remain++; should this error out in userspace if we end up at zero? +-m quota --quota 18446744073709551615 --remain 18446744073709551614;;FAIL this one really should also pass... kernel has: if (atomic64_read(&q->counter) > q->quota + 1) this should probably be: if (atomic64_read(&q->counter) && atomic64_read(&q->counter) - 1 > q->quota) Also I think there's something ugly with -m quota --quota 18446744073709551614 vs -m quota --quota 18446744073709551615 and thus possibly: if (current_count <= skb->len) { should actually be if (current_count && current_count <= skb->len) { Maybe all of this would actually be easier if we were counting bytes used instead of bytes remaining.