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The bcachefs filesystem, and the process for getting it upstream, were the topics of a session led remotely by Kent Overstreet, creator of bcachefs, at the 2023 Linux Storage, Filesystem, Memory-Management and BPF Summit. He has also discussed bcachefs in previous editions of the summit, first in 2018 and at last year's event; in both of those cases, the question of getting bcachefs merged into the mainline kernel came up, but that merge has not happened yet. This time around, though, Overstreet seemed closer than ever to being ready to actually start that process.

The kernel's "direct map" makes the entirety of a system's physical memory available in the kernel's virtual address space. Normally, huge pages are used for this mapping, making it relatively efficient to access. Increasingly, though, there is a need to carve some pages out of the direct map; this splits up those huge pages and makes the system as a whole less efficient. During a memory-management session at the 2022 Linux Storage, Filesystem, Memory-management and BPF Summit (LSFMM), Mike Rapoport led a session on direct-map fragmentation and how it might be avoided.

The kernel's direct map makes all of a system's physical memory available to the kernel within its address space — on 64-bit systems, at least. This seemingly simple feature has proved to be hard to maintain, in the face of the requirements faced by current systems, while keeping good performance. The latest attempt to address this issue is this patch set from Mike Rapoport adding more direct-map awareness to the kernel's page allocator.