Re: kcmp(2)

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

>>> Don't cloner instances differ in minor number?  [...]
>> Not that I?m aware of.  [...]
> Well, as noted in this thread, traditionally you can tell when two
> files are the same by examining stat results.

Maybe that should be a hint.  See below.

> And the cloner mechanism replaced an older scheme where you had to
> pick the number of instances you wanted, and unless I'm
> misremembering badly in that world each had to have its own minor
> number.

That's my understanding as well.

> That said, it almost certainly isn't important...

Well, if it means that with a minor tweak NetBSD could have kcmp(3)
instead of kcmp(2), it could be.

It occurs to me that, if you give each device_t a unique-per-boot
serial number and return that in structs stat, writing a kcmp(3) would
border on trivial.  (The _implementation_ would be NetBSD-specific, in
that it would depend on st_serial or whatever you call it, but the
_interface_ wouldn't.)

Except, hmm.  The above covers only DTYPE_VNODE.  I'm not sure what
could be done about other DTYPEs.  If you really want to support
Linuxisms - IMO that way lies madness, but it's ben somewhere between a
long time and forever since NetBSD cared about MO - it might have to be
kcmp(2) in order to DTRT for all DTYPEs.  Or else each DTYPE would need
its own analog of st_serial.  Perhaps st_serial could be done in a way
that's common across all DTYPEs?  It'd probably need to be 64-bit to
avoid running out in the face of extreme use cases, but that's hardly
impossible.

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