Bcachefs may be headed out of the kernel

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.

At the same time, many VM and containerization solutions build these features themselves. It seems attractive to reuse the heavily optimized machinery that a COW filesystem offers. And indeed at least Docker can use Btrfs snapshots to create images. It has been a while since I looked into it though; no clue how mature and performant it is nowadays.

https://docs.docker.com/engine/storage/drivers/btrfs-driver/

I want the default file system everywhere be CoW and snapshot-enabled (a perfection would have snapshot on the file and directory level) so that tooling starts to assume it is available and begins to use it.

Technological progress comes from us all being lifted to new levels and higher standards, I think. The Bcachefs/Btrfs niche is the standard we want/expect now and I think people are right to imagine it, develop it and make it happen.

Funnily enough Windows went there with NTFS and full-fledged transactional FS and registry APIs with snapshots and rollbacks:

https://learn.microsoft.com/en-us/windows/win32/fileio/about...

But then for some reason it was all deprecated in Win11.