Thread by @DanielMicay

Unfortunately, some users upgrading from this cancelled beta release may encounter a broken upgrade path to the next beta release where the device forces you to do a factory reset. This is caused by downgrading the kernel, but we're unsure exactly why.

Our suspicion is that the backport of f2fs made changes to the on-disk format that are not backwards compatible with the previous version. It's seemingly only an issue on a subset of users on the Pixel 3a and Pixel 3a XL. This does not impact people that aren't beta testing.

We always test the future upgrade path before pushing out a release to the beta channel. However, in this case the upgrade path is being broken by reverting a large set of changes that proved to be too problematic for us to ship rather than waiting for Android 11 as a whole.

Not really sure what else we can do beyond pushing out this release and accepting that some of the beta testers on the Pixel 3a and 3a XL are going to need to do a factory reset in order to upgrade to this next beta release, which doesn't have any of these problems anymore.

These issues demonstrate why the beta testing is so important. Testing betas is an important kind of contribution to the project, but if you're doing it, it's important to follow along with our news, make regular backups (do that now!) and upgrade when you can deal with issues.

I think some people using the beta channel without thinking much about they're doing will be upset with these problems, but there's not much we can do about it. Need to get out the next beta release with the resolution for these issues and then work on getting it out to stable.

It would be difficult to fully narrow down and then somehow hack around the issue that makes downgrading the kernel force a factory reset for some users. We made the mistake of not anticipating so many breaking changes to userspace ABI including apparently f2fs format changes.