Filesystems

Kent Overstreet, who was banned from Linux 6.13 due to disagreements with other kernel developers, has submitted a patchset for kernel 6.12. He hopes to be able to remove bcachefs' Experimental tag in 2025 [17]. In Linux 6.12, XFS achieves an important goal that people have been pursuing for 16 years. Changes to the Virtual File System (VFS) block size code now enable block sizes that exceed the system page size (large block sizes). In the future, it will presumably also be possible to enable these advances in VFS block sizes for other filesystems [18].

NFS has experienced performance improvements through the integration of the LOCALIO extension. The protocol can be used to determine whether the client and server are located on the same host. If this is the case, the network Remote Procedure Call (RPC) protocol can be bypassed, resulting in significantly higher transfer rates. This is the case, for example, for containerized workloads that run on the same server as the NFS daemon providing storage [19].

The integration of Rust into the kernel has made progress in terms of its support for handling CPU mitigations. Retpoline, Straight-Line Speculation (SLS), and Rethunk are now handled by Rust code. In addition, support for the Kernel Address Sanitizer (KASAN), kernel control flow integrity (KCFI), and shadow call sanitizers has been implemented in Rust [20].

Conclusions and Outlook

Linux 6.12 is in the upper-middle range in terms of its size, but it does come with some significant developments that will benefit users. Besides mainlining the PREEMPT_RT patchset, the benefits mainly relate to the sched_ext extensible scheduler and initial support for the Raspberry Pi 5. As always, the Kernel Newbies website [21] provides an overview of all the new features in Linux 6.12.

The release of Linux 6.12 also heralded the opening of the two-week merge window for its successor, Linux 6.13, with the first kernel released in January 2025. Among other things, Linux 6.13 adds real-time capabilities for the Loongarch architecture and removes the ReiserFS filesystem code from the kernel, reducing the kernel's size by about 32,800 lines [22].