Bcachefs may be headed out of the kernel

Does the filesystem actually need to be part of the kernel project to work? I can see where you'd need that for the root filesystem, but even then, couldn't one migrate an existing installation to a new partition with a different filesystem?

We ZFS for that. What we want is something in kernel, ready to go, 100% supported on root ok any Linux system with no license ambiguity. We want to replace ext4. Maybe btrfs can do it. I hear it has outgrown its rocky puberty.

Bcachefs and Btrfs are not really competing with Ext4. There are basically 2 filesystem niches.

First niche is the full featured CoW filesystem; it has snapshots, detects and repairs corruption, transparent compression, all that good stuff.

The other niche is being an allocator of sectors. There's one storage device, divide it up amongst all these processes asking for storage. That's Ext4: an allocator of disk sectors, dressed up in a filesystem API. When you are running databases or VMs, all you want is an allocator of sectors. You don't want lots of stuff getting in the way of your writes. You don't want checksumming, you don't want your writes going to a new place every time. You just want write access to part of the disk.

I want COW everywhere because I want to revert to snapshots on my laptop as much as on my servers. I want it integrated into the bootloader and boot into snapshots, I want ransomware protection on my laptop, etc.