Upcoming ABI Breakage in RELENG_7

[Heiko Wundram]

Am Mittwoch, 30. Juli 2008 13:03:34 schrieb Ronald Klop:
> I think in this case (the ABI breakage) it is more nice to say: "If you
> don't know what to do, you wil probably not see any problem because of
> this."
> The edge case of what can go wrong is so small, that you must be doing
> quite specialized stuff to see breakage. In that case you would understand
> what is going on. (IMHO)

Err, no.

As someone else has already noted, a prominent KLM that's distributed 
separately from the kernel which uses the vnode structure extensively (which 
I didn't think of at all until I read the respective mail) is fuse. A 
pre-upgrade compiled fuse is most certainly going to break because of this 
change. Some people have dual installations of Windows/FreeBSD (at least I'd 
presume that's the case with the fiddlers like me that track -STABLE as a 
hobby, not as a developer, or those developers who program for Windows as a 
day-job, also like me) who use ntfs-3g to mount their NTFS-data; 
additionally, I also extensively use ssh-fs, which is also fuse-based, and I 
guess there are also others who use it, and so the reach of this ABI-change, 
at least IMHO, is much larger than the original message makes you believe.

Now, after the update, a lot can go wrong, because the fuse KLM is loaded by 
an init-script, and your system is most probably going to Oops while booting 
if you didn't think of disabling the fuse init-script before you update your 
kernel, and will NOT fail "gracefully". If the respective person doesn't know 
how he/she should boot to single-user-mode, update rc.conf to disable this, 
reboot, rebuild the module to get the system back up, the only thing I can 
possibly say is: "don't track stable."

It might've sounded a bit harsh what I wrote, but tracking -STABLE means 
knowing your system enough so that you know how to fix things if they come 
back to bite you (especially after getting a HEADS UP). And that doesn't seem 
to be the case here if the respective person asks for SPECIFIC instructions 
what to do.

So, again: DON'T track -STABLE if you can't fix the system if it breaks, and 
AFAICT this change is most certainly going to break quite a few systems.

-- 
Heiko Wundram