bcachefs: enable in-tree module and add userspace-tools sysext#4136
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ananthb wants to merge 5 commits into
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bcachefs: enable in-tree module and add userspace-tools sysext#4136ananthb wants to merge 5 commits into
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Pull request overview
Adds a new optional Flatcar systemd-sysext (flatcar-bcachefs) that bundles the bcachefs userspace tools and out-of-tree kernel module, built from a vendored Gentoo sys-fs/bcachefs-tools ebuild and registered in the extra sysext build matrix.
Changes:
- Vendor
sys-fs/bcachefs-tools-1.38.6intoportage-stable(ebuild, metadata, Manifest). - Add sysext build integration: env override for kernel-binpkg installs, sysext mangle script, and registration in
extra_sysexts.sh. - Add a user-facing changelog entry describing enablement and kernel floor (≥ 6.16).
Reviewed changes
Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| sdk_container/src/third_party/portage-stable/sys-fs/bcachefs-tools/metadata.xml | Adds Gentoo package metadata for the vendored bcachefs tools ebuild. |
| sdk_container/src/third_party/portage-stable/sys-fs/bcachefs-tools/Manifest | Adds distfile checksums (bcachefs tarball + Rust crates) needed for offline builds. |
| sdk_container/src/third_party/portage-stable/sys-fs/bcachefs-tools/bcachefs-tools-1.38.6.ebuild | Introduces the vendored build recipe including optional module build via linux-mod-r1. |
| sdk_container/src/third_party/coreos-overlay/coreos/config/env/sys-fs/bcachefs-tools | Ensures kernel version/env is preserved for module builds when installing from binpkgs. |
| build_library/sysext_mangle_flatcar-bcachefs | Prunes non-runtime files, relocates /usr/sbin payload, and wires module loading via shared helper. |
| build_library/extra_sysexts.sh | Registers the new sysext in the extra sysext build list (amd64, USE=modules). |
| changelog/changes/2026-07-08-bcachefs.md | Documents the new extension, enablement, and kernel version floor for users. |
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ananthb
changed the title
Introduces a `flatcar-bcachefs` sysext following the shape of the existing `flatcar-zfs` sysext. Ships both the bcachefs userspace utilities and the bcachefs.ko kernel module, built together from a single ebuild against the exact kernel Flatcar's SDK produces. Files: - sdk_container/.../portage-stable/sys-fs/bcachefs-tools/: verbatim vendor of Gentoo's sys-fs/bcachefs-tools 1.38.6 from the main tree. Gentoo's ebuild has MODULES_OPTIONAL_IUSE=+modules and inherits linux-mod-r1, so with USE="modules" (default-on) it produces both the userspace binaries and bcachefs.ko in one pass. - sdk_container/.../coreos-overlay/coreos/config/env/sys-fs/bcachefs-tools: the same SKIP_KERNEL_BINPKG_ENV_RESET / LINUX_INFO_BINARY_RESET env pattern used by sys-fs/zfs-kmod so binpkg installs pick up Flatcar's kernel headers correctly. - build_library/sysext_mangle_flatcar-bcachefs: prunes dev/debug bits and calls the shared configure_modprobe helper (from sysext_mangle_kmod) to wire bcachefs.ko through the overlay-based modprobe helper — same shape as the ZFS mangle script. - build_library/extra_sysexts.sh: registers `bcachefs|sys-fs/bcachefs-tools|modules|amd64`. amd64-only for now; arm64 keywording follows once upstream marks it stable. - changelog/changes/2026-07-08-bcachefs.md: user-facing note. Kernel requirement: bcachefs's DKMS harness has BUILD_EXCLUSIVE_KERNEL_MIN=6.16, so the sysext will only build cleanly on channels whose kernel meets that floor (currently alpha). This is enforced by the ebuild — no additional gating is added here. Stable and lts channels will start producing the sysext once their kernels reach 6.16+. Background: bcachefs was mainlined in Linux 6.7 and removed in 6.18 after Kent Overstreet moved it to a DKMS-shape out-of-tree module. See https://lwn.net/Articles/1040120/ for the removal context. bcachefs is pre-1.0 for on-disk format stability, so this sysext is opt-in (users enable it by writing 'bcachefs' to /etc/flatcar/enabled-sysext.conf) and not supported for the root partition — matching the ZFS experimental posture. Signed-off-by: Ananth Bhaskararaman <antsub@gmail.com>
Registering bcachefs in EXTRA_SYSEXTS unconditionally would let the ebuild's MODULES_KERNEL_MIN=6.16 refusal abort create_prod_sysexts() on channels whose kernel is older, since the loop runs under set -e with no per-sysext gating. Extend the EXTRA_SYSEXTS schema with an optional fifth min_kernel field and skip entries whose requirement outpaces the board's coreos-kernel version. Also fix the /usr/sbin relocation in the mangle script: mv ./usr/sbin/* misses Portage .keep* placeholders, leaving the directory non-empty and making the following rmdir fail under set -e. cp -a src/. dst/ includes dotfiles, and rm -rf tolerates emptiness. Signed-off-by: Ananth Bhaskararaman <antsub@gmail.com>
Kent Overstreet's plan for bcachefs (1.38.7+) makes out-of-tree module builds impractical: once Rust becomes a hard dependency (kernel 7.0), DKMS needs an exact rustc match, the Rust stdlib sources, bindgen and the kernel build's .rlib/.rmeta artifacts. Flatcar builds its own kernel and can sidestep the whole mess by enabling bcachefs in-tree. Enable CONFIG_BCACHEFS_FS=m (and CONFIG_BCACHEFS_POSIX_ACL=y to match btrfs's shape) in coreos-modules commonconfig-6.12 so bcachefs.ko ships with the base image and is loaded on demand via modprobe. Rework the sysext to userspace-only: - extra_sysexts.sh: drop the `modules` USE flag (explicit `-modules`) and the min_kernel gate — the ebuild refuses to build below 6.16 only when it builds the OOT module, which we no longer do. - prod_image_util.sh: revert the min_kernel schema field; it existed solely to gate this sysext. - sysext_mangle_flatcar-bcachefs: drop configure_modprobe wiring, no OOT module to install. - coreos/config/env/sys-fs/bcachefs-tools: delete; the KV env dance was needed only for module builds against the board root's kernel. Keep the dotfile-safe /usr/sbin relocation (Portage .keep* under set -e). Update the changelog to describe the new shape. Signed-off-by: Ananth Bhaskararaman <antsub@gmail.com>
- src_unpack(): the previous flow ran `unpacker ${P}.tar.zst` and then
`cargo_src_unpack`, which itself iterates ${A} and re-extracts the
tarball. With USE=verify-sig the .sign file also lands in ${A} and
cargo's per-file unpack chokes on it. Fold everything into a single
pass: verify-sig streams the tarball into tar during signature check,
and we then hand cargo_src_unpack an ${A} with the tarball / .sign
filtered out. In the non-verify-sig path cargo_src_unpack extracts
the tarball itself.
- Drop `[[ -e bcachefs ]] && die` in src_compile: the workaround is
purely defensive against upstream's mangled symlink; killing the
build once upstream stops mangling would be an unnecessary trap.
`ln -rsf` is idempotent — just force the link.
- metadata.xml: drop the `fuse` USE flag entry. The ebuild does not
declare `IUSE=fuse` and the FUSE bits are unconditionally included,
so the flag entry only produces QA warnings.
Signed-off-by: Ananth Bhaskararaman <antsub@gmail.com>
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Address a second round of Copilot review feedback: - `src_install`: switch `into /` → `into /usr` and retarget all six compat symlinks (fsck/mkfs/mount plus the .fuse.* variants) from /sbin to /usr/sbin. `build_sysext` prunes every non-/usr top-level before running the mangle script, so anything installed to /sbin was quietly getting dropped from the final sysext. On usrmerge systems (Flatcar, modern Gentoo) this doesn't change what users see on disk since /sbin unifies with /usr/sbin — but it lets the mangle script's existing /usr/sbin → /usr/bin relocation catch the whole payload. - `QA_FLAGS_IGNORED`: retarget /sbin/bcachefs → /usr/sbin/bcachefs so the QA ignore still matches the actual install path. - `MODULES_OPTIONAL_IUSE=+modules` → `MODULES_OPTIONAL_IUSE=modules`: make the DKMS/OOT module build opt-in. With Flatcar shipping CONFIG_BCACHEFS_FS=m in coreos-modules, the ebuild's CONFIG_CHECK refuses to build the module (`!BCACHEFS_FS`). A default `emerge sys-fs/bcachefs-tools` would fail unless users remembered to pass USE=-modules; flipping the default keeps `emerge` working out of the box for the userspace tools. `extra_sysexts.sh` still passes `USE="-modules"` explicitly as belt-and-suspenders in case a profile force-enables it. Signed-off-by: Ananth Bhaskararaman <antsub@gmail.com>
| @@ -0,0 +1 @@ | |||
| - Enabled the in-tree bcachefs kernel module (`CONFIG_BCACHEFS_FS=m` with POSIX ACLs) and provided a companion bcachefs Flatcar extension as an optional systemd-sysext image with the release. Write `bcachefs` to `/etc/flatcar/enabled-sysext.conf` through Ignition and the sysext will be installed during provisioning; it ships the userspace utilities (`mkfs.bcachefs`, `mount.bcachefs`, ...) that pair with the kernel module. bcachefs is still experimental (pre-1.0 on-disk format) and is not supported for the root partition. | |||
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| if use verify-sig; then | ||
| # Upstream signs the uncompressed tarball. Stream-verify the | ||
| # detached signature while extracting the tarball via tee, | ||
| # leaving the source tree in place. | ||
| einfo "Verifying and unpacking ${P}.tar.zst ..." | ||
| verify-sig_verify_detached - "${DISTDIR}"/${P}.tar.sign \ | ||
| < <(zstd -fdc "${DISTDIR}"/${P}.tar.zst | tee >(tar -xf -)) | ||
| assert "Unpack failed" | ||
| # Filter the tarball and its detached signature out of ${A} | ||
| # so cargo_src_unpack doesn't re-extract the tarball or feed | ||
| # the .sign file to unpack (which would die). | ||
| local A=${A//${P}.tar.zst/} | ||
| A=${A//${P}.tar.sign/} | ||
| fi |
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Summary
Ships bcachefs on Flatcar as:
bcachefs.kobuilt in-tree withcoreos-modules(CONFIG_BCACHEFS_FS=m,CONFIG_BCACHEFS_POSIX_ACL=y). The module is part of the base image and loads on demand viamodprobe.flatcar-bcachefssysext that carries the bcachefs userspace utilities (bcachefs,mkfs.bcachefs,fsck.bcachefs,mount.bcachefs, ...).Users opt into the tools by writing
bcachefsto/etc/flatcar/enabled-sysext.conf. The kernel module is available on every Flatcar image whether or not the sysext is merged.amd64-only
Keeping the sysext amd64-only until arm64 stabilizes. The kernel module itself is architecture-neutral in Kconfig, so it will also be available on arm64 images without any further config change.
Test plan
emerge sys-kernel/coreos-modulesbuilds cleanly with the new config;olddefconfigdoesn't downgradeBCACHEFS_FSton(i.e., everyselected dep is satisfied by the existing config).bcachefs.koviamodprobe bcachefsandgrep bcachefs /proc/filesystemsreports it.USE=\"-modules\" emerge sys-fs/bcachefs-toolsproduces/usr/bin/bcachefsand the compat symlinks without touching any kernel module tree.flatcar-bcachefssysext exposesmkfs.bcachefs,mount.bcachefs, etc.mkfs.bcachefson a loopback file +mount -t bcachefsround-trip.