Bcachefs Fixes Deadlock In Recovery, More Fixes Coming

Following the revised Bcachefs code making it into Linux 6.9 and a warning for Bcachefs multi-device users to move past Linux 6.7, a batch of fixes was merged overnight for Linux 6.9 while further fixes to this file-system are expected soon.

Bcachefs maintainer Kent Overstreet sent in an initial batch of fixes to the file-system for Linux 6.9. He explained in that pull request:

Going to have a larger pull for you soon with some new repair code - some users got hit bad with the failure to downgrade bug (the fix for which is still not in 6.7) - that caused the splitbrain detection to attempt to kick out every device from the filesystem, and some users attempted to run in very_degraded mode got things very borked.

For users:
- there's a no_splitbrain_check option which runs the splitbrain checks in dry run mode, that should suffice to get most people going
- if your fs is very borked, 'scan entire device for btree nodes and reconstruct' is almost done; it looks like that will be a pretty bulletproof way to reconstruct.

Some poeple may have their filesystems unavailable for a bit but I'm trying to make sure no one looses data, and no one should be forced to migrate either, we should always get back to a working functional rw fs.

With last night's merge request having assorted bug fixes, but most significant is a fix for a deadlock in recovery mode when there is a need to rewrite large numbers of btree inodes to fix errors.