Bcachefs file system apparently remains stagnant in Linux

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After repeated disagreements with the developer of the Bcachefs file system, Linus Torvalds has now declared the Bcachefs code of Linux as "externally maintained". The label is a novelty – and since the inventor and lead developer of the kernel has not explained it in detail, it is unclear what exactly it means. However, the generally expected removal of Bcachefs support, which is considered experimental in Linux, and which Torvalds has repeatedly held out the prospect of, appears to be off the table for the time being.

No direct code ejection

At the same time, however, the new award also indicates that the Bcachefs code preserved in the kernel will not be changed significantly for the time being – It will therefore remain at the level of Linux 6.16, as Torvalds had not integrated the changes that Bcachefs developer Kent Overstreet had submitted for the version 6.17 currently being prepared. However, users already using Bcachefs can safely switch to 6.17 and later kernel versions by remaining –. This approach avoids a "regression" for users, which is prohibited in Linux development because it is a major thorn in Torvalds' side.

Caution is advised when using the externally maintained Bcachefs

Kernel updates work without problems, at least as long as users and distributions do not use kernels with newer Bcachefs code that is maintained externally by Overstreet: This or associated userspace tools could make incompatible changes to the file system structures if used once, whereupon the Bcachefs code of the official kernel should then refuse to mount the file system.

In principle, it would be possible for someone else to act as an intermediary and take newer Bcachefs code from Overstreet and send it to Torvalds for inclusion in Linux, where it would be maintained. However, such a person would probably quickly get caught between the fronts, which would make the work enormously difficult. A while ago there was a Bcachefs co-developer who was apparently willing to take on such a position – but he turned his back on Bcachefs development after a dispute with Overstreet.

Cause of the friction

Kent Overstreet had fallen out with Torvalds, among other things, because he repeatedly submitted major changes for inclusion during the stabilization phase of new kernel versions. From Torvalds' point of view, these were dangerous and should therefore have waited a few weeks until the start of development of the next version. Hundreds of other kernel developers have mastered this development model largely without any problems for decades. Overstreet also had several disputes with these developers in the context of Bcachefs development, for example because he changed Linux kernel code maintained by them without adequate consultation or even behind their backs. Over a decade ago, Bcachefs' predecessor Bcache also had its share of disputes with Overstreet – until the latter gave up support for the SSD hard disk cache solution Bcache and turned to Bcachefs without having built up a successor.

The patch description for the new status at Bcachefs and some voices in the kernel environment indicated that Torvalds took the course of action now implemented in consultation with other central Linux developers. It remains to be seen what impact the move will have on the Linux world. Large distributors such as Debian, Fedora or openSUSE will continue to use the Bcachefs included in Linux or disable it completely in their kernels. It is unlikely that these overstreets will incorporate newer Bcachefs code, as this complicates maintenance. In addition, even more kernel developers are likely to refuse bug reports submitted by users of the distributions because such modifications can easily lead to errors. These should not occur with the official kernel. However, individual smaller distributions will probably not shy away from this in order to specifically address fans of Bcachefs.

(nie)