Why Is Linux Kernel Likely to Drop Bcachefs After a Heated Clash?

Background

Linus Torvalds warned that Linux kernel 6.16 could be the last release to adopt the new disk format, hinting that the kernel may part ways with Bcachefs in the 6.17 merge window.

About Bcachefs

Bcachefs is an emerging copy‑on‑write (COW) file system for Linux, led by Kent Overstreet, who previously created the block‑caching layer Bcache. The project reuses about 80% of Bcache code and was merged into the mainline kernel in version 6.7.

It aims to combine modern features from ZFS and Btrfs with the performance of traditional file systems like ext4 and XFS, but since its inclusion it has suffered numerous stability problems.

The Conflict

During the 6.16‑rc phase, Kent submitted a patch named “journal‑rewind” that added new functionality rather than fixing bugs, violating the kernel’s rule that only bug‑fixes are allowed after the merge window closes. Linus responded angrily, stating that if the patch were merged, Bcachefs would be removed in the next merge window.

Kent defended the patch as essential for data‑integrity, arguing that the rules should be flexible for critical fixes. The email exchange grew increasingly hostile, with Kent using coarse language toward Linus and Linus insisting on strict adherence to the merge‑window policy.

Other senior developers, including ext4 maintainer Theodore Ts’o, criticized Kent’s approach, emphasizing that the kernel community has long upheld the merge‑window conventions and that no individual should receive special treatment.

Community Opinions

Some observers argue that the rules are clear and that Bcachefs should not expect exceptions.

Others note Kent’s technical skill but question his collaborative attitude.

Many users express distrust in Bcachefs’s maturity and prefer to stick with proven file systems like ext4.

Conclusion and Outlook

Even if Bcachefs is removed from the mainline, the project can continue externally. Developers may build custom kernels with Bcachefs, use the FUSE subsystem to run it outside the kernel, or employ DKMS to compile it on demand. The controversy highlights the tension between innovative file‑system development and the disciplined processes that keep the Linux kernel stable.