containerd/cri: enable the btrfs snapshotter (#4316)

.github/workflows/snapshotter.yaml

+name: Snapshotter Testing
+on:
+  push:
+    paths-ignore:
+      - "install.sh"
+      - "tests/cgroup2/**"
+      - "tests/install/**"
+      - "tests/integration/**"
+      - "tests/unitcoverage/**"
+  pull_request:
+    paths-ignore:
+      - "install.sh"
+      - "tests/cgroup2/**"
+      - "tests/install/**"
+      - "tests/integration/**"
+      - "tests/unitcoverage/**"
+  workflow_dispatch: {}
+jobs:
+  build:
+    name: "Build"
+    runs-on: ubuntu-20.04
+    timeout-minutes: 40
+    steps:
+      - name: "Checkout"
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 1
+      - name: "Build"
+        run: DOCKER_BUILDKIT=1 SKIP_VALIDATE=1 make
+      - name: "Upload Binary"
+        uses: actions/upload-artifact@v2
+        with:
+          name: k3s
+          path: dist/artifacts/k3s
+      - name: "Upload Images"
+        uses: actions/upload-artifact@v2
+        with:
+          name: k3s-airgap-images-amd64.tar
+          path: dist/artifacts/k3s-airgap-images-amd64.tar
+  test:
+    name: "Test"
+    # nested virtualization is only available on macOS hosts
+    runs-on: macos-10.15
+    needs: build
+    timeout-minutes: 40
+    strategy:
+      matrix:
+        vm: [opensuse-leap]
+    steps:
+      - name: "Checkout"
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 1
+      - name: "Download Binary"
+        uses: actions/download-artifact@v2
+        with:
+          name: k3s
+          path: dist/artifacts/
+      - name: "Download Images"
+        uses: actions/download-artifact@v2
+        with:
+          name: k3s-airgap-images-amd64.tar
+          path: dist/artifacts/
+      - name: "Vagrant Plugin(s)"
+        working-directory: tests/snapshotter/btrfs/${{ matrix.vm }}
+        run: vagrant plugin install vagrant-k3s
+      - name: "Vagrant VM"
+        working-directory: tests/snapshotter/btrfs/${{ matrix.vm }}
+        env:
+          VAGRANT_EXPERIMENTAL: disks
+        run: vagrant up

Dockerfile.dapper

@@ -11,7 +11,7 @@ ENV no_proxy=$no_proxy
 RUN apk -U --no-cache add bash git gcc musl-dev docker vim less file curl wget ca-certificates jq linux-headers \
     zlib-dev tar zip squashfs-tools npm coreutils python3 openssl-dev libffi-dev libseccomp libseccomp-dev \
     libseccomp-static make libuv-static sqlite-dev sqlite-static libselinux libselinux-dev zlib-dev zlib-static \
-    zstd gzip alpine-sdk binutils-gold
+    zstd gzip alpine-sdk binutils-gold btrfs-progs-dev btrfs-progs-static
 RUN if [ "$(go env GOARCH)" = "arm64" ]; then                                                               \
     wget https://github.com/aquasecurity/trivy/releases/download/v0.16.0/trivy_0.16.0_Linux-ARM64.tar.gz && \
     tar -zxvf trivy_0.16.0_Linux-ARM64.tar.gz                                                            && \

go.sum

@@ -155,6 +155,7 @@ github.com/cockroachdb/logtags v0.0.0-20190617123548-eb05cc24525f/go.mod h1:i/u9
 github.com/container-storage-interface/spec v1.5.0 h1:lvKxe3uLgqQeVQcrnL2CPQKISoKjTJxojEs9cBk+HXo=
 github.com/container-storage-interface/spec v1.5.0/go.mod h1:8K96oQNkJ7pFcC2R9Z1ynGGBB1I93kcS6PGg3SsOk8s=
 github.com/containerd/aufs v1.0.0/go.mod h1:kL5kd6KM5TzQjR79jljyi4olc1Vrx6XBlcyj3gNv2PU=
+github.com/containerd/btrfs v1.0.0 h1:osn1exbzdub9L5SouXO5swW4ea/xVdJZ3wokxN5GrnA=
 github.com/containerd/btrfs v1.0.0/go.mod h1:zMcX3qkXTAi9GI50+0HOeuV8LU2ryCE/V2vG/ZBiTss=
 github.com/containerd/cgroups v1.0.1 h1:iJnMvco9XGvKUvNQkv88bE4uJXxRQH18efbKo9w5vHQ=
 github.com/containerd/cgroups v1.0.1/go.mod h1:0SJrPIenamHDcZhEcJMNBB85rHcUsw4f25ZfBiPYRkU=

pkg/containerd/builtins_linux.go

@@ -24,6 +24,7 @@ import (
 	_ "github.com/containerd/containerd/runtime/v2/runc/options"
 	_ "github.com/containerd/containerd/snapshots/native/plugin"
 	_ "github.com/containerd/containerd/snapshots/overlay/plugin"
+	_ "github.com/containerd/containerd/snapshots/btrfs/plugin"
 	_ "github.com/containerd/fuse-overlayfs-snapshotter/plugin"
 	_ "github.com/containerd/stargz-snapshotter/service/plugin"
 )

scripts/build

@@ -42,7 +42,7 @@ STATIC="
 STATIC_SQLITE="
     -extldflags '-static -lm -ldl -lz -lpthread'
 "
-TAGS="ctrd apparmor seccomp no_btrfs netcgo osusergo providerless"
+TAGS="ctrd apparmor seccomp netcgo osusergo providerless"
 RUNC_TAGS="apparmor seccomp"
 RUNC_STATIC="static"
 

tests/snapshotter/btrfs/opensuse-leap/Vagrantfile

+# -*- mode: ruby -*-
+# vi: set ft=ruby :
+#
+
+ENV['TEST_VM_NAME'] ||= 'snapshotter-btrfs'
+ENV['TEST_VM_HOSTNAME'] ||= 'test'
+
+Vagrant.configure("2") do |config|
+  config.vagrant.plugins = {
+    'vagrant-k3s' => {:version => '~> 0.1.3'},
+  }
+  config.vm.define ENV['TEST_VM_NAME'], primary: true do |test|
+    test.vm.box = "opensuse/Leap-15.3.x86_64"
+    test.vm.hostname = ENV['TEST_VM_HOSTNAME']
+    test.vm.provision 'k3s-prepare', type: 'shell', run: 'once', privileged: true do |sh|
+      sh.inline = <<~EOF
+        #!/usr/bin/env bash
+        set -eu -o pipefail
+        zypper install -y btrfsprogs hostname
+        mkdir -p /var/lib/rancher/k3s /etc/rancher/k3s /usr/local/bin
+        if ! mountpoint -q /var/lib/rancher/k3s; then
+            : ${BTRFS_DEV:=#{ENV['BTRFS_DEV']}}
+            for disk in sd[b-d] vd[b-d] xd[b-d]; do
+                if [ -n "${BTRFS_DEV}" ]; then break; fi
+                : ${BTRFS_DEV:=$(test -b /dev/$disk && echo $disk)}
+            done
+            btrfs filesystem show /dev/${BTRFS_DEV:?unable to determine automatically, please specify} 2>/dev/null || mkfs -t btrfs /dev/${BTRFS_DEV}
+            mountpoint -q /mnt || mount -t btrfs /dev/${BTRFS_DEV} /mnt
+            btrfs subvolume show /mnt/@k3s 2>/dev/null || btrfs subvolume create /mnt/@k3s
+            umount /mnt
+            mount -t btrfs -o subvol=@k3s /dev/${BTRFS_DEV} /var/lib/rancher/k3s
+        fi
+        if [ -e /vagrant/k3s ]; then
+            cp -vf /vagrant/k3s /usr/local/bin/
+            chmod -v +x /usr/local/bin/k3s
+        fi
+        if [ -e /vagrant/*.tar ]; then
+            mkdir -vp /var/lib/rancher/k3s/agent/images
+            for tar in /vagrant/*.tar; do
+                cp -vf $tar /var/lib/rancher/k3s/agent/images/
+            done
+        fi
+      EOF
+    end
+    test.vm.provision 'k3s-install', type: 'k3s', run: 'once' do |k3s|
+      k3s.args = %w[server --snapshotter=btrfs]
+      k3s.env = %w[INSTALL_K3S_NAME=server INSTALL_K3S_SKIP_DOWNLOAD=true K3S_TOKEN=vagrant]
+      k3s.config = {
+        'disable' => %w[local-storage metrics-server servicelb traefik],
+        'disable-helm-controller' => true,
+        'disable-network-policy' => true,
+        'write-kubeconfig-mode' => '0644',
+      }
+      k3s.config_mode = '0644' # side-step https://github.com/k3s-io/k3s/issues/4321
+    end
+    test.vm.provision "k3s-ready", type: "shell", run: "once" do |sh|
+      sh.env = { :PATH => "/usr/local/bin:/usr/local/sbin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin" }
+      sh.inline = <<~SHELL
+        #!/usr/bin/env bash
+        set -eu -o pipefail
+        echo 'Waiting for node to be ready ...'
+        time timeout 120 bash -c 'while ! (kubectl wait --for condition=ready node/$(hostname) 2>/dev/null); do sleep 5; done'
+        time timeout 300 bash -c 'while ! (kubectl --namespace kube-system rollout status --timeout 10s deploy/coredns 2>/dev/null); do sleep 5; done'
+      SHELL
+    end
+    test.vm.provision "k3s-status", type: "shell", run: "once" do |sh|
+      sh.env = { :PATH => "/usr/local/bin:/usr/local/sbin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin" }
+      sh.inline = <<~SHELL
+        #!/usr/bin/env bash
+        set -eux -o pipefail
+        kubectl get node,all -A -o wide
+        btrfs subvolume list /var/lib/rancher/k3s/agent/containerd/io.containerd.snapshotter.v1.btrfs
+      SHELL
+    end
+  end
+
+  %w[hyperv libvirt virtualbox vmware_desktop].each do |p|
+    config.vm.provider p do |v|
+      v.cpus = ENV['CPUS'] || 2
+      v.memory = ENV['MEMORY'] || 2048
+    end
+  end
+
+  config.vm.provider :hyperv do |v,o|
+    o.vm.disk :disk, name: "btrfs", size: "8GB" # Requires VAGRANT_EXPERIMENTAL="disks"
+  end
+
+  config.vm.provider :libvirt do |v,o|
+    v.storage :file, :size => '8G'
+  end
+
+  config.vm.provider :virtualbox do |v,o|
+    v.gui = false
+    v.check_guest_additions = false
+    o.vm.disk :disk, name: "btrfs", size: "8GB" # Requires VAGRANT_EXPERIMENTAL="disks"
+  end
+
+  config.vm.synced_folder '../../../../dist/artifacts', '/vagrant', type: 'rsync', disabled: ['1', 'true'].include?(ENV['RSYNC_DISABLE']),
+    rsync__exclude: ENV['RSYNC_EXCLUDE'] || '*.tar.*'
+end

vendor/github.com/containerd/btrfs/.gitignore

+# Compiled Object files, Static and Dynamic libs (Shared Objects)
+*.o
+*.a
+*.so
+bin/
+
+# Folders
+_obj
+_test
+
+# Architecture specific extensions/prefixes
+*.[568vq]
+[568vq].out
+
+*.cgo1.go
+*.cgo2.c
+_cgo_defun.c
+_cgo_gotypes.go
+_cgo_export.*
+
+_testmain.go
+
+*.exe
+*.test
+*.prof
+
+# Support running go modules in vendor mode for local development
+/vendor/

vendor/github.com/containerd/btrfs/Makefile

+#   Copyright The containerd Authors.
+
+#   Licensed under the Apache License, Version 2.0 (the "License");
+#   you may not use this file except in compliance with the License.
+#   You may obtain a copy of the License at
+
+#       http://www.apache.org/licenses/LICENSE-2.0
+
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an "AS IS" BASIS,
+#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#   See the License for the specific language governing permissions and
+#   limitations under the License.
+
+
+.PHONY: clean binaries generate lint vet test
+all: vet lint test binaries
+
+binaries: bin/btrfs-test
+
+vet:
+	go vet ./...
+
+lint:
+	golint ./...
+
+test:
+	go test -v ./...
+
+bin/%: ./cmd/% *.go
+	go build -o ./$@ ./$<
+
+clean:
+	rm -rf bin/*

vendor/github.com/containerd/btrfs/README.md

+# go-btrfs
+
+[![PkgGoDev](https://pkg.go.dev/badge/github.com/containerd/btrfs)](https://pkg.go.dev/github.com/containerd/btrfs)
+[![Build Status](https://github.com/containerd/btrfs/workflows/CI/badge.svg)](https://github.com/containerd/btrfs/actions?query=workflow%3ACI)
+[![Go Report Card](https://goreportcard.com/badge/github.com/containerd/btrfs)](https://goreportcard.com/report/github.com/containerd/btrfs)
+
+Native Go bindings for btrfs.
+
+# Status
+
+These are in the early stages. We will try to maintain stability, but please
+vendor if you are relying on these directly.
+
+# Contribute
+
+This package may not cover all the use cases for btrfs. If something you need
+is missing, please don't hesitate to submit a PR.
+
+Note that due to struct alignment issues, this isn't yet fully native.
+Preferably, this could be resolved, so contributions in this direction are
+greatly appreciated.
+
+## Applying License Header to New Files
+
+If you submit a contribution that adds a new file, please add the license
+header. You can do so manually or use the `ltag` tool:
+
+
+```console
+$ go get github.com/kunalkushwaha/ltag
+$ ltag -t ./license-templates
+```
+
+The above will add the appropriate licenses to Go files. New templates will
+need to be added if other kinds of files are added. Please consult the
+documentation at https://github.com/kunalkushwaha/ltag
+
+## Project details
+
+btrfs is a containerd sub-project, licensed under the [Apache 2.0 license](./LICENSE).
+As a containerd sub-project, you will find the:
+ * [Project governance](https://github.com/containerd/project/blob/master/GOVERNANCE.md),
+ * [Maintainers](https://github.com/containerd/project/blob/master/MAINTAINERS),
+ * and [Contributing guidelines](https://github.com/containerd/project/blob/master/CONTRIBUTING.md)
+
+information in our [`containerd/project`](https://github.com/containerd/project) repository.

vendor/github.com/containerd/btrfs/btrfs.c

+/*
+  Copyright The containerd Authors
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+#include <stddef.h>
+#include <linux/magic.h>
+#include <btrfs/ioctl.h>
+#include <btrfs/ctree.h>
+
+#include "btrfs.h"
+
+void unpack_root_item(struct gosafe_btrfs_root_item* dst, struct btrfs_root_item* src) {
+	memcpy(dst->uuid, src->uuid, BTRFS_UUID_SIZE);
+	memcpy(dst->parent_uuid, src->parent_uuid, BTRFS_UUID_SIZE);
+	memcpy(dst->received_uuid, src->received_uuid, BTRFS_UUID_SIZE);
+	dst->gen = btrfs_root_generation(src);
+	dst->ogen = btrfs_root_otransid(src);
+	dst->flags = btrfs_root_flags(src);
+}
+
+/* unpack_root_ref(struct gosafe_btrfs_root_ref* dst, struct btrfs_root_ref* src) { */

vendor/github.com/containerd/btrfs/btrfs.h

+/*
+  Copyright The containerd Authors
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+#include <stddef.h>
+#include <linux/magic.h>
+#include <btrfs/ioctl.h>
+#include <btrfs/ctree.h>
+
+// unfortunately, we need to define "alignment safe" C structs to populate for
+// packed structs that aren't handled by cgo. Fields will be added here, as
+// needed.
+
+struct gosafe_btrfs_root_item {
+	u8 uuid[BTRFS_UUID_SIZE];
+	u8 parent_uuid[BTRFS_UUID_SIZE];
+	u8 received_uuid[BTRFS_UUID_SIZE];
+
+	u64 gen;
+	u64 ogen;
+	u64 flags;
+};
+
+void unpack_root_item(struct gosafe_btrfs_root_item* dst, struct btrfs_root_item* src);
+/* void unpack_root_ref(struct gosafe_btrfs_root_ref* dst, struct btrfs_root_ref* src); */

vendor/github.com/containerd/btrfs/doc.go

+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+// Package btrfs provides bindings for working with btrfs partitions from Go.
+package btrfs

vendor/github.com/containerd/btrfs/go.mod

+module github.com/containerd/btrfs
+
+go 1.15
+
+require github.com/pkg/errors v0.9.1

vendor/github.com/containerd/btrfs/go.sum

+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=

vendor/github.com/containerd/btrfs/helpers.go

+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package btrfs
+
+/*
+#include <stddef.h>
+#include <btrfs/ioctl.h>
+#include <btrfs/ctree.h>
+*/
+import "C"
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"os"
+	"strings"
+	"unsafe"
+
+	"github.com/pkg/errors"
+)
+
+func subvolID(fd uintptr) (uint64, error) {
+	var args C.struct_btrfs_ioctl_ino_lookup_args
+	args.objectid = C.BTRFS_FIRST_FREE_OBJECTID
+
+	if err := ioctl(fd, C.BTRFS_IOC_INO_LOOKUP, uintptr(unsafe.Pointer(&args))); err != nil {
+		return 0, err
+	}
+
+	return uint64(args.treeid), nil
+}
+
+var (
+	zeroArray = [16]byte{}
+	zeros     = zeroArray[:]
+)
+
+func uuidString(uuid *[C.BTRFS_UUID_SIZE]C.u8) string {
+	b := (*[maxByteSliceSize]byte)(unsafe.Pointer(uuid))[:C.BTRFS_UUID_SIZE]
+
+	if bytes.Equal(b, zeros) {
+		return ""
+	}
+
+	return fmt.Sprintf("%x-%x-%x-%x-%x", b[:4], b[4:4+2], b[6:6+2], b[8:8+2], b[10:16])
+}
+
+func findMountPoint(path string) (string, error) {
+	fp, err := os.Open("/proc/self/mounts")
+	if err != nil {
+		return "", err
+	}
+	defer fp.Close()
+
+	const (
+		deviceIdx = 0
+		pathIdx   = 1
+		typeIdx   = 2
+		options   = 3
+	)
+
+	var (
+		mount   string
+		scanner = bufio.NewScanner(fp)
+	)
+
+	for scanner.Scan() {
+		fields := strings.Fields(scanner.Text())
+		if fields[typeIdx] != "btrfs" {
+			continue // skip non-btrfs
+		}
+
+		if strings.HasPrefix(path, fields[pathIdx]) {
+			mount = fields[pathIdx]
+		}
+	}
+
+	if scanner.Err() != nil {
+		return "", scanner.Err()
+	}
+
+	if mount == "" {
+		return "", errors.Errorf("mount point of %v not found", path)
+	}
+
+	return mount, nil
+}

vendor/github.com/containerd/btrfs/info.go

+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package btrfs
+
+// Info describes metadata about a btrfs subvolume.
+type Info struct {
+	ID         uint64 // subvolume id
+	ParentID   uint64 // aka ref_tree
+	TopLevelID uint64 // not actually clear what this is, not set for now.
+	Offset     uint64 // key offset for root
+	DirID      uint64
+
+	Generation         uint64
+	OriginalGeneration uint64
+
+	UUID         string
+	ParentUUID   string
+	ReceivedUUID string
+
+	Name string
+	Path string // absolute path of subvolume
+	Root string // path of root mount point
+
+	Readonly bool // true if the snaps hot is readonly, extracted from flags
+}
+
+type infosByID []Info
+
+func (b infosByID) Len() int           { return len(b) }
+func (b infosByID) Less(i, j int) bool { return b[i].ID < b[j].ID }
+func (b infosByID) Swap(i, j int)      { b[i], b[j] = b[j], b[i] }

vendor/github.com/containerd/btrfs/ioctl.go

+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package btrfs
+
+import "syscall"
+
+func ioctl(fd, request, args uintptr) error {
+	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, fd, request, args)
+	if errno != 0 {
+		return errno
+	}
+	return nil
+}

vendor/github.com/containerd/containerd/snapshots/btrfs/plugin/plugin.go

+// +build linux,!no_btrfs,cgo
+
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package plugin
+
+import (
+	"errors"
+
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+
+	"github.com/containerd/containerd/platforms"
+	"github.com/containerd/containerd/plugin"
+	"github.com/containerd/containerd/snapshots/btrfs"
+)
+
+// Config represents configuration for the btrfs plugin.
+type Config struct {
+	// Root directory for the plugin
+	RootPath string `toml:"root_path"`
+}
+
+func init() {
+	plugin.Register(&plugin.Registration{
+		ID:     "btrfs",
+		Type:   plugin.SnapshotPlugin,
+		Config: &Config{},
+		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
+			ic.Meta.Platforms = []ocispec.Platform{platforms.DefaultSpec()}
+
+			config, ok := ic.Config.(*Config)
+			if !ok {
+				return nil, errors.New("invalid btrfs configuration")
+			}
+
+			root := ic.Root
+			if len(config.RootPath) != 0 {
+				root = config.RootPath
+			}
+
+			ic.Meta.Exports = map[string]string{"root": root}
+			return btrfs.NewSnapshotter(root)
+		},
+	})
+}

vendor/modules.txt

@@ -174,6 +174,8 @@ github.com/cilium/ebpf/internal/unix
 github.com/cilium/ebpf/link
 # github.com/container-storage-interface/spec v1.5.0
 github.com/container-storage-interface/spec/lib/go/csi
+# github.com/containerd/btrfs v1.0.0 => github.com/containerd/btrfs v1.0.0
+github.com/containerd/btrfs
 # github.com/containerd/cgroups v1.0.1 => github.com/containerd/cgroups v1.0.1
 ## explicit
 github.com/containerd/cgroups
@@ -345,6 +347,8 @@ github.com/containerd/containerd/services/snapshots
 github.com/containerd/containerd/services/tasks
 github.com/containerd/containerd/services/version
 github.com/containerd/containerd/snapshots
+github.com/containerd/containerd/snapshots/btrfs
+github.com/containerd/containerd/snapshots/btrfs/plugin
 github.com/containerd/containerd/snapshots/native
 github.com/containerd/containerd/snapshots/native/plugin
 github.com/containerd/containerd/snapshots/overlay