=== Originally posted on twitter at x.com/bob_beck/status/1077103234815160320 ==

Twas the night before Christmas
And in my abode
There were bugs to be chased
Through the VFS code

The kernel was running
My diffs in as a test
Could put it in snapshots
And hope for the best

My vnodes were locked
With vput and vget
Vref and vrele
For reference count checks

When in my right window
There spewed a great wail
Of regression test errors
A big bag of fail

I jumped into emacs
And grabbed the test output
To look for some info
to chase down the problem

When what
To my wandering eyes
Should appear
But a DDB prompt
Dumb shit you crashed here

A kernel page fault trap
With backtrace below it
Showed vget had followed
NULL pointer and blown it

While traverseing dot dot
Into filesystem other
I had copied a NULL up
from mnt_vnodecovered

I spoke not a word,
But with a small curse
I added a test
For this vnode traverse

I adjusted some cases
To fix a few nits
And the regress test failures
Then baked a new diff

I ran it through regress
And checked for the crashes
It might just be ready
To mail to the masses

So I sent out the diff
And I poured out a drink
Happy Christmas for OpenBSD Hackers
I think...