Comment 50 for bug 1906476

>So to be clear this patch revert fixes the issue being caused new, but, if the issue already >happened on your filesystem it will continue to occur because the exception is reporting >corruption on disk. I don't currently

I don't think that's quite correct--- like the OP I can boot an older kernel, with a pre-regression ZFS driver (ZFS 2.02), with the same filesystem(s) (and the same/newest userspace library and utility versions) on the same hardware and it works quite happily, without any error or warning messages. I'm not at all convinced that the error message truly indicates irreparable filesystem damage--- there may not even be anything wrong at all with the on-disk data structures, only in the driver's in-memory reconstruction or interpretation of them.

I hit this bug after allowing a 20.04 LTS installation to upgrade from a 5.11.0-7620-generic kernel to the 5.13.0-7614-generic in stable. The panics occurred on every boot attempt under 5.13.0, at the same fairly early point in the boot process (first page of kernel messages) every time. Rebooting with 5.11.0 doesn't generate any errors and has been running stably for over two weeks (as it did for months before the failed attempt to upgrade to 5.13.0). The 5.11.0 build reports ZFS module version v2.0.2-1ubuntu5, while the 5.13.0 has 2.0.3-8ubuntu6. My zfs package family is all 0.8.3-1ubuntu12.12.

It's annoying to get a regression like this in an LTS kernel, but at least reverting is easy and seems effective.