Re: udev and devfs - The final word

Rob Love
2004-01-01T15:22:55Z

On Thu, 2004-01-01 at 07:34, Rob Landley wrote:

> Fundamental problem: "Unique" depends on the other devices in the system. You
> can't guarantee unique by looking at one device, more or less by definition.

Of course.

> Combine that with hotplug and you have a world of pain. Generating a number
> from a device is just a fancy hashing function, but as soon as you have two
> devices that generate the same number independently (when in separate
> systems) and you plug them both into the same system: boom.

A solution would have to deal with collisions.

> Of course the EASY way to deal with collisions is to just fail the hash thingy
> in a detectable way, and punt to some kind of udev override. So if you yank
> a drive from system A, throw it in system B, try to re-export it NFS, and
> it's not going to work, it TELLS you.

No no no. Nothing this complicated. No punting to udev.

> Solve 90% of the problem space and have a human deal with the exceptions. How
> big's the unique number being exported, anyway? (If it's 32 bits, the
> exceptions are 1 in 4 billion. It may never be seen in the wild...)

Device numbers are 64-bit now.

Rob Love