Linus Torvalds hints Bcachefs may get dropped from the Linux kernel

Kernel 6.16 may be the last with the new disk format

The geek titans are clashing once again, and Linux supremo Linus Torvalds has warned: "I think we'll be parting ways" as of kernel 6.17.

The latest installment in the continuing drama over the next-gen bcachefs filesystem is that Torvalds accepted the code, for now, but added a sobering warning:

I have pulled this, but also as per that discussion, I think we'll be parting ways in the 6.17 merge window.

You made it very clear that I can't even question any bug-fixes and I should just pull anything and everything.

Honestly, at that point, I don't really feel comfortable being involved at all, and the only thing we both seemed to really fundamentally agree on in that discussion was "we're done."

The Linux kernel is the world's biggest FOSS project, thanks in part to the strong control exerted by Torvalds himself. There's a process, although it's not something that is formally documented and described. Like Linux itself, this process has evolved over time. Each time a new point-release of the kernel comes out, Torvalds starts work on the next one. He opens what's termed a merge window, as The Register described a few years ago.

During that time window, developers submit new code for inclusion. Then follows a series of work-in-progress test releases, with rc for "release candidate" on the end of the version number: right now, we're on 6.16-rc4. Code submissions – in the terminology of the Git revision-control system, "pull requests" – continue during that time, but they are meant to be bug fixes and only bug fixes.

This time around, bcachefs maintainer Kent Overstreet submitted a PR that included some new functionality. That's a big no-no: the RC phase is for fixing stuff sent in during the merge window. Torvalds was not happy, but Overstreet, as he tends to, didn't back down but rather defended the change.

Overstreet has been rebuked before; indeed, he was barred from contributing to kernel 6.13 in November 2024. Linux Weekly News summarizes what's happening and we link to that because Overstreet himself appears to be defending his moves at some length in the article comments.

The bcachefs saga has been going on for a decade now; The Reg first reported on it in August 2015. Now, after finally being included in kernel 6.7 in January 2024, it looks possible that it could get kicked out again.

If this happens, it does not spell the end of the bcachefs project. In fact, there are several potential ways forward, as discussed in the LWN comments. It could continue as an external development. In order to use it, there are multiple possibilities. People wanting to try it could build their own custom, modified kernels.

In another scenario, a version could be built that used the FUSE subsystem, which allows filesystem code to run outside of the kernel itself. That works and it's been optimized in recent years, but it's substantially slower than in-kernel code. Alternatively, the code could be built on demand when the kernel is updated: there's a standard tool for this, called DKMS, which is how people running the Nvidia display drivers get them.

Or, potentially, the dispute between these two genius-level personalities could get resolved… but no amount of code will help there. ®