Filesystems and case-insensitivity

No, you can't do it in userspace. The kernel does not have directory locking, which you'd need for an atomic "create a file while making sure that there is no other file with the same name (case-insensitive)" operation. Thus if you create "makefile" you need to scan the whole directory for any other matching filename, and that *still* doesn't stop anybody from introducing consistency errors (you can race to create "Makefile" and "MakeFile" at the same time).