Re: udev and devfs - The final word

Linus Torvalds
2004-01-05T02:53:12Z

On Sun, 4 Jan 2004, Andries Brouwer wrote:
>
> Surprise! Are you leaving POSIX? Or ditching NFS?
> Or demanding that NFS servers must never reboot?

Ok, Andries, time for you to take a deep breath, and calm down. Because
your arguments are getting ridiculous in the extreme.

A NFS server is sure as hell not going to export _its_ dynamic /dev to its
clients. That would be not just stupid, but crazy. Next you tell me that
you were using devfs and exporting that over NFS.

A NFS server is going to export something _totally_ different than its own
/dev directory - it needs to be _client_-specific anyway. That's true with
stable numbers too, btw - ever tried to mount a Solaris /dev on a Linux
client? No workee.

> A common Unix idiom is testing for the identity
> of two files by comparing st_ino and st_dev.
> A broken idiom?

No. It still works. Even if the device numbers change across reboots.

Why? Becuase that _program_ sure as hell isn't running across a reboot.

And again, this is not something we haven't seen before. Have you ever
looked at the "st_dev" values? Try once - look at what it returns for a
NFS-mounted filesystem. Ponder. Notice how it already is NOT stable across
reboots.

In other words, the stuff you're complaining about is all stuff that
nobody has _ever_ been able to rely on, and that has nothign to do with
udev or anythign else. It all just shows how 100% right I am for saying
that you cannot rely on stable numbers.

So I repeat: calm down, and think it through.

Linus