Wouldn't this have been caught by an exhaustive unit test or even a fuzz test? I don't know what kind of testing practices are applied to projects like zfs, nor what kinds or amounts of tests functions like this are subject to, but I would imagine that especially for low-level functions like this, unit tests with all of the known edge cases would be written.
(yes this is very much an armchair opinion, I mostly do front-end JS for a living)
Yeah that surprised me too - I would have assumed that ZFS had a bunch of "store and retrieve" tests in many different configurations that would have caught this.
(yes this is very much an armchair opinion, I mostly do front-end JS for a living)