by George Whittaker Introduction After years of debate and development, bcachefs—a modern copy-on-write filesystem once merged into the Linux kernel—is being removed from mainline. As of kernel 6.17, the in-kernel implementation has been excised, and future use is expected via an out-of-tree DKMS module. This marks a turning point for the bcachefs project, raising questions about its stability, adoption, and relationship with the kernel development community. In this article, we’ll explore the background of bcachefs, the sequence of events leading to its removal, the technical and community dynamics involved, and implications for users, distributions, and the filesystem’s future. What Is Bcachefs? Before diving into the removal, let’s recap what bcachefs is and why it attracted attention. Origin & goals: Developed by Kent Overstreet, bcachefs emerged from ideas in the earlier bcache project (a block-device caching layer). It aimed to build a full-featured, general-purpose filesystem co