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btrfs-devel

This directory contains the fs/btrfs/ subtree from kdave/btrfs-devel — the upstream Linux kernel development tree for BTRFS.

Purpose

It serves two roles in this repository:

  1. Build reference — the btrfs-dwarfs/ kernel module can be compiled against this tree instead of the system kernel headers, which is useful for testing against bleeding-edge BTRFS APIs before they land in a distribution kernel:

    # Build btrfs_dwarfs.ko against the in-tree btrfs-devel source
make -C btrfs-dwarfs kernel-devel

  2. Source reference — the internal BTRFS data structures and APIs used by btrfs-dwarfs/ (partition backends, blend layer) are documented here. When upstream changes an API, this tree shows the new signature.

Runtime dependency

This directory is not a runtime dependency. At runtime, the BTRFS kernel module is the one built into (or loaded by) the Linux distribution running inside the microVM. Any modern distribution kernel (≥ 5.15) includes BTRFS.

The userspace tools (btrfs-progs) are installed inside the VM by the cloud-init setup in linuxfs/.

Keeping in sync

To pull the latest fs/btrfs/ from upstream:

# From the repository root
git fetch btrfs-devel master
BTRFS_TREE=$(git ls-tree btrfs-devel/master fs/btrfs | awk '{print $3}')
git read-tree --prefix=btrfs-devel/ -u "${BTRFS_TREE}"
git commit -m "btrfs-devel: sync with kdave/btrfs-devel $(date +%Y-%m-%d)"

License

The files in this directory are part of the Linux kernel and are licensed under GPL-2.0-only. See individual file headers.