Merge pull request #7254 from mxpv/go

Switch to Go 1.19

.github/workflows/build-test-images.yml

@@ -39,7 +39,7 @@ jobs:
     steps:
       - uses: actions/setup-go@v2
         with:
-          go-version: '1.18.5'
+          go-version: '1.19'
 
       - uses: actions/checkout@v2
         with:

.github/workflows/ci.yml

@@ -12,7 +12,7 @@ on:
 env:
   # Go version we currently use to build containerd across all CI.
   # Note: don't forget to update `Binaries` step, as it contains the matrix of all supported Go versions.
-  GO_VERSION: '1.18.5'
+  GO_VERSION: '1.19'
 
 jobs:
   #
@@ -35,7 +35,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: golangci/golangci-lint-action@v3
         with:
-          version: v1.46.2
+          version: v1.48.0
           skip-cache: true
           args: --timeout=5m
 
@@ -219,7 +219,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-18.04, macos-12, windows-2019, windows-2022]
-        go-version: ['1.17.13', '1.18.5']
+        go-version: ['1.19', '1.18.5']
     steps:
       - uses: actions/setup-go@v2
         with:
@@ -415,13 +415,13 @@ jobs:
       - name: Install containerd dependencies
         env:
           RUNC_FLAVOR: ${{ matrix.runc }}
-          GOFLAGS: -modcacherw
         run: |
           sudo apt-get install -y gperf
-          sudo -E PATH=$PATH script/setup/install-seccomp
-          sudo -E PATH=$PATH script/setup/install-runc
-          sudo -E PATH=$PATH script/setup/install-cni $(grep containernetworking/plugins go.mod | awk '{print $2}')
-          sudo -E PATH=$PATH script/setup/install-critools
+          script/setup/install-seccomp
+          script/setup/install-runc
+          script/setup/install-cni $(grep containernetworking/plugins go.mod | awk '{print $2}')
+          script/setup/install-critools
+          script/setup/install-failpoint-binaries
 
       - name: Install criu
         run: |
@@ -429,10 +429,6 @@ jobs:
           sudo apt-get update
           sudo apt-get install -y criu
 
-      - name: Install failpoint binaries
-        run: |
-          script/setup/install-failpoint-binaries
-
       - name: Install containerd
         env:
           CGO_ENABLED: 1
@@ -440,7 +436,7 @@ jobs:
           make binaries GO_BUILD_FLAGS="-mod=vendor"
           sudo -E PATH=$PATH make install
 
-      - run: sudo -E PATH=$PATH script/setup/install-gotestsum
+      - run: script/setup/install-gotestsum
       - name: Tests
         env:
           GOPROXY: direct
@@ -540,7 +536,7 @@ jobs:
         with:
           go-version: ${{ env.GO_VERSION }}
       - uses: actions/checkout@v2
-      - run: sudo -E PATH=$PATH script/setup/install-gotestsum
+      - run: script/setup/install-gotestsum
       - name: Tests
         env:
           GOPROXY: direct

.github/workflows/codeql.yml

@@ -26,7 +26,7 @@ jobs:
 
     - uses: actions/setup-go@v2
       with:
-        go-version: 1.18.5
+        go-version: 1.19
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL

.github/workflows/images.yml

@@ -24,7 +24,7 @@ jobs:
     steps:
       - uses: actions/setup-go@v2
         with:
-          go-version: '1.18.5'
+          go-version: '1.19'
 
       - uses: actions/checkout@v2
         with:

.github/workflows/nightly.yml

@@ -7,7 +7,7 @@ on:
       - '.github/workflows/nightly.yml'
 
 env:
-  GO_VERSION: '1.18.5'
+  GO_VERSION: '1.19'
 
 jobs:
   linux:

.github/workflows/release.yml

@@ -6,7 +6,7 @@ on:
 name: Containerd Release
 
 env:
-  GO_VERSION: '1.18.5'
+  GO_VERSION: '1.19'
 
 jobs:
   check:

.zuul/playbooks/containerd-build/integration-test.yaml

@@ -2,7 +2,7 @@
   become: yes
   roles:
   - role: config-golang
-    go_version: '1.18.5'
+    go_version: '1.19'
     arch: arm64
   tasks:
   - name: Install pre-requisites

.zuul/playbooks/containerd-build/run.yaml

@@ -2,7 +2,7 @@
   become: yes
   roles:
   - role: config-golang
-    go_version: '1.18.5'
+    go_version: '1.19'
     arch: arm64
   tasks:
   - name: Build containerd

.zuul/playbooks/containerd-build/unit-test.yaml

@@ -2,7 +2,7 @@
   become: yes
   roles:
   - role: config-golang
-    go_version: '1.18.5'
+    go_version: '1.19'
     arch: arm64
   tasks:
   - name: Build and test containerd

Vagrantfile

@@ -97,7 +97,7 @@ EOF
   config.vm.provision "install-golang", type: "shell", run: "once" do |sh|
     sh.upload_path = "/tmp/vagrant-install-golang"
     sh.env = {
-        'GO_VERSION': ENV['GO_VERSION'] || "1.18.5",
+        'GO_VERSION': ENV['GO_VERSION'] || "1.19",
     }
     sh.inline = <<~SHELL
         #!/usr/bin/env bash

content/local/store.go

@@ -34,7 +34,7 @@ import (
 	"github.com/containerd/containerd/log"
 	"github.com/sirupsen/logrus"
 
-	digest "github.com/opencontainers/go-digest"
+	"github.com/opencontainers/go-digest"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
@@ -643,7 +643,6 @@ func (s *store) ingestRoot(ref string) string {
 // - root: entire ingest directory
 // - ref: name of the starting ref, must be unique
 // - data: file where data is written
-//
 func (s *store) ingestPaths(ref string) (string, string, string) {
 	var (
 		fp = s.ingestRoot(ref)

contrib/Dockerfile.test

@@ -10,7 +10,7 @@
 #
 # docker build -t containerd-test --build-arg RUNC_VERSION=v1.0.0-rc94 -f Dockerfile.test ../
 
-ARG GOLANG_VERSION=1.18.5
+ARG GOLANG_VERSION=1.19
 ARG GOLANG_IMAGE=golang
 
 FROM ${GOLANG_IMAGE}:${GOLANG_VERSION} AS golang

contrib/fuzz/daemon.go

@@ -13,6 +13,7 @@
    See the License for the specific language governing permissions and
    limitations under the License.
 */
+
 package fuzz
 
 import (

contrib/fuzz/oss_fuzz_build.sh

@@ -40,11 +40,11 @@ compile_fuzzers() {
 
 apt-get update && apt-get install -y wget
 cd $SRC
-wget --quiet https://go.dev/dl/go1.18.5.linux-amd64.tar.gz
+wget --quiet https://go.dev/dl/go1.19.linux-amd64.tar.gz
 
 mkdir temp-go
 rm -rf /root/.go/*
-tar -C temp-go/ -xzf go1.18.5.linux-amd64.tar.gz
+tar -C temp-go/ -xzf go1.19.linux-amd64.tar.gz
 mv temp-go/go/* /root/.go/
 cd $SRC/containerd
 

filters/filter.go

@@ -65,7 +65,6 @@
 // ```
 // name==foo,labels.bar
 // ```
-//
 package filters
 
 import (

filters/parser.go

@@ -45,7 +45,6 @@ field     := quoted | [A-Za-z] [A-Za-z0-9_]+
 operator  := "==" | "!=" | "~="
 value     := quoted | [^\s,]+
 quoted    := <go string syntax>
-
 */
 func Parse(s string) (Filter, error) {
 	// special case empty to match all

filters/quote.go

@@ -31,10 +31,10 @@ var errQuoteSyntax = errors.New("quote syntax error")
 // or character literal represented by the string s.
 // It returns four values:
 //
-//	1) value, the decoded Unicode code point or byte value;
-//	2) multibyte, a boolean indicating whether the decoded character requires a multibyte UTF-8 representation;
-//	3) tail, the remainder of the string after the character; and
-//	4) an error that will be nil if the character is syntactically valid.
+//  1. value, the decoded Unicode code point or byte value;
+//  2. multibyte, a boolean indicating whether the decoded character requires a multibyte UTF-8 representation;
+//  3. tail, the remainder of the string after the character; and
+//  4. an error that will be nil if the character is syntactically valid.
 //
 // The second argument, quote, specifies the type of literal being parsed
 // and therefore which escaped quote character is permitted.

integration/failpoint/cmd/cni-bridge-fp/main_linux.go

@@ -20,7 +20,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"os"
 	"path/filepath"
 	"syscall"
@@ -168,7 +168,7 @@ func (c *failpointControl) updateTx(updateFn func(conf *failpointConf) error) er
 	}
 	defer unflock(f.Fd())
 
-	data, err := ioutil.ReadAll(f)
+	data, err := io.ReadAll(f)
 	if err != nil {
 		return fmt.Errorf("failed to read failpoint setting %s: %w", c.confPath, err)
 	}

metadata/buckets.go

@@ -46,10 +46,13 @@
 // the structure is changed in addition to adding a migration and incrementing
 // the database version.
 // Notes:
-//  * `╘══*...*` refers to maps with arbitrary keys
-//  * `version` is a key to a numeric value identifying the minor revisions
+//
+//   - `╘══*...*` refers to maps with arbitrary keys
+//
+//   - `version` is a key to a numeric value identifying the minor revisions
 //     of schema version
-//  * a namespace in a schema bucket cannot be named "version"
+//
+//   - a namespace in a schema bucket cannot be named "version"
 //
 //     └──v1                                        - Schema version bucket
 //     ├──version : <varint>                     - Latest version, see migrations
@@ -107,16 +110,16 @@
 //     │        └──expected : <digest>        - Expected commit digest
 //     └──leases
 //     ╘══*lease id*
-//              ├──createdat : <binary time>     - Created at
+//     ├──createdat : <binary time>     - Created at
 //     ├──labels
 //     │  ╘══*key* : <string>           - Label value
-//              ├──snapshots
+//     ├──snapshots
 //     │  ╘══*snapshotter*
 //     │     ╘══*snapshot key* : <nil>  - Snapshot reference
-//              ├──content
+//     ├──content
 //     │  ╘══*blob digest* : <nil>      - Content blob reference
 //     └──ingests
-//                 ╘══*ingest reference* : <nil> - Content ingest reference
+//     ╘══*ingest reference* : <nil> - Content ingest reference
 package metadata
 
 import (

namespaces/store.go

@@ -24,8 +24,6 @@ import "context"
 // oriented. A namespace is really just a name and a set of labels. Objects
 // that belong to a namespace are returned when the namespace is assigned to a
 // given context.
-//
-//
 type Store interface {
 	Create(ctx context.Context, namespace string, labels map[string]string) error
 	Labels(ctx context.Context, namespace string) (map[string]string, error)

oci/spec_opts.go

@@ -591,6 +591,7 @@ func WithNamespacedCgroup() SpecOpts {
 
 // WithUser sets the user to be used within the container.
 // It accepts a valid user string in OCI Image Spec v1.0.0:
+//
 //	user, uid, user:group, uid:gid, uid:group, user:gid
 func WithUser(userstr string) SpecOpts {
 	return func(ctx context.Context, client Client, c *containers.Container, s *Spec) error {

pkg/apparmor/apparmor.go

@@ -18,6 +18,7 @@ package apparmor
 
 // HostSupports returns true if apparmor is enabled for the host, // On non-Linux returns false
 // On Linux returns true if apparmor_parser is enabled, and if we
+//
 //	are not running docker-in-docker.
 //
 //	It is a modified version of libcontainer/apparmor.IsEnabled(), which does not

pkg/cri/opts/spec.go

@@ -77,6 +77,7 @@ func WithProcessArgs(config *runtime.ContainerConfig, image *imagespec.ImageConf
 
 // mounts defines how to sort runtime.Mount.
 // This is the same with the Docker implementation:
+//
 //	https://github.com/moby/moby/blob/17.05.x/daemon/volumes.go#L26
 type orderedMounts []*runtime.Mount
 

pkg/cri/streaming/server.go

@@ -45,7 +45,7 @@ import (
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 
-	restful "github.com/emicklei/go-restful/v3"
+	"github.com/emicklei/go-restful/v3"
 
 	"k8s.io/apimachinery/pkg/types"
 	remotecommandconsts "k8s.io/apimachinery/pkg/util/remotecommand"
@@ -165,6 +165,7 @@ func NewServer(config Config, runtime Runtime) (Server, error) {
 		Addr:              s.config.Addr,
 		Handler:           s.handler,
 		TLSConfig:         s.config.TLSConfig,
+		ReadHeaderTimeout: 3 * time.Second, // Fix linter G112: Potential Slowloris Attack because ReadHeaderTimeout is not configured in the http.Server
 	}
 
 	return s, nil

pkg/ioutil/write_closer.go

@@ -73,9 +73,9 @@ func (n *nopWriteCloser) Close() error {
 // serialWriteCloser wraps a write closer and makes sure all writes
 // are done in serial.
 // Parallel write won't intersect with each other. Use case:
-// 1) Pipe: Write content longer than PIPE_BUF.
+//  1. Pipe: Write content longer than PIPE_BUF.
 //     See http://man7.org/linux/man-pages/man7/pipe.7.html
-// 2) <3.14 Linux Kernel: write is not atomic
+//  2. <3.14 Linux Kernel: write is not atomic
 //     See http://man7.org/linux/man-pages/man2/write.2.html
 type serialWriteCloser struct {
 	mu sync.Mutex

pkg/os/os_windows.go

@@ -32,6 +32,7 @@ import (
 //   - os.Open on a directory returns a os.File where Fd() is a search handle from FindFirstFile.
 //   - syscall.Open does not provide a way to specify FILE_FLAG_BACKUP_SEMANTICS, which is needed to
 //     open a directory.
+//
 // We could use os.Open if the path is a file, but it's easier to just use the same code for both.
 // Therefore, we call windows.CreateFile directly.
 func openPath(path string) (windows.Handle, error) {
@@ -58,6 +59,7 @@ func openPath(path string) (windows.Handle, error) {
 }
 
 // GetFinalPathNameByHandle flags.
+//
 //nolint:revive // SNAKE_CASE is not idiomatic in Go, but aligned with Win32 API.
 const (
 	cFILE_NAME_OPENED = 0x8

platforms/platforms.go

@@ -42,7 +42,7 @@
 //
 // More details of the specifier syntax and platform spec follow.
 //
-// Declaring Platform Support
+// # Declaring Platform Support
 //
 // Components that have strict platform requirements should use the OCI
 // platform specification to declare their support. Typically, this will be
@@ -60,7 +60,7 @@
 // specification when in doubt). ARM should set variant under certain
 // discussions, which are outlined below.
 //
-// Platform Specifiers
+// # Platform Specifiers
 //
 // While the OCI platform specifications provide a tool for components to
 // specify structured information, user input typically doesn't need the full
@@ -77,7 +77,7 @@
 // where the architecture may be known but a runtime may support images from
 // different operating systems.
 //
-// Normalization
+// # Normalization
 //
 // Because not all users are familiar with the way the Go runtime represents
 // platforms, several normalizations have been provided to make this package
@@ -95,7 +95,7 @@
 //
 // We also normalize the operating system `macos` to `darwin`.
 //
-// ARM Support
+// # ARM Support
 //
 // To qualify ARM architecture, the Variant field is used to qualify the arm
 // version. The most common arm version, v7, is represented without the variant

process.go

@@ -72,8 +72,10 @@ type ExitStatus struct {
 
 // Result returns the exit code and time of the exit status.
 // An error may be returned here to which indicates there was an error
+//
 //	at some point while waiting for the exit status. It does not signify
 //	an error with the process itself.
+//
 // If an error is returned, the process may still be running.
 func (s ExitStatus) Result() (uint32, time.Time, error) {
 	return s.code, s.exitedAt, s.err

script/setup/install-cni

@@ -25,6 +25,12 @@ CNI_COMMIT=${1:-$(grep containernetworking/plugins "$GOPATH"/src/github.com/cont
 CNI_DIR=${DESTDIR:=''}/opt/cni
 CNI_CONFIG_DIR=${DESTDIR}/etc/cni/net.d
 
+# e2e and Cirrus will fail with "sudo: command not found"
+SUDO=''
+if (( $EUID != 0 )); then
+    SUDO='sudo'
+fi
+
 TMPROOT=$(mktemp -d)
 git clone https://github.com/containernetworking/plugins.git "${TMPROOT}"/plugins
 pushd "${TMPROOT}"/plugins
@@ -32,8 +38,8 @@ git checkout "$CNI_COMMIT"
 ./build_linux.sh
 mkdir -p $CNI_DIR
 cp -r ./bin $CNI_DIR
-mkdir -p $CNI_CONFIG_DIR
-cat << EOF | tee $CNI_CONFIG_DIR/10-containerd-net.conflist
+$SUDO mkdir -p $CNI_CONFIG_DIR
+$SUDO cat << EOF | $SUDO tee $CNI_CONFIG_DIR/10-containerd-net.conflist
 {
   "cniVersion": "1.0.0",
   "name": "containerd-net",

script/setup/install-critools

@@ -22,6 +22,12 @@ set -eu -o pipefail
 
 script_dir="$(cd -- "$(dirname -- "$0")" > /dev/null 2>&1; pwd -P)"
 
+# e2e will fail with "sudo: command not found"
+SUDO=''
+if (( $EUID != 0 )); then
+    SUDO='sudo'
+fi
+
 cd "$(go env GOPATH)"
 go install github.com/onsi/ginkgo/v2/ginkgo@v2.1.4
 
@@ -33,10 +39,10 @@ git clone https://github.com/kubernetes-sigs/cri-tools.git "${TMPROOT}/cri-tools
 pushd "${TMPROOT}"/cri-tools
 git checkout "$CRITEST_COMMIT"
 make
-make install -e DESTDIR="${DESTDIR}" BINDIR=/usr/local/bin
+$SUDO make install -e DESTDIR="${DESTDIR}" BINDIR=/usr/local/bin
 
 mkdir -p "${DESTDIR}/etc/"
-cat << EOF | tee "${DESTDIR}/etc/crictl.yaml"
+$SUDO cat << EOF | $SUDO tee "${DESTDIR}/etc/crictl.yaml"
 runtime-endpoint: unix:///run/containerd/containerd.sock
 EOF
 

script/setup/install-dev-tools

@@ -24,7 +24,7 @@ set -eu -o pipefail
 go install github.com/containerd/protobuild@v0.2.0
 go install github.com/containerd/protobuild/cmd/go-fix-acronym@v0.2.0
 go install github.com/cpuguy83/go-md2man/v2@v2.0.1
-go install github.com/golangci/golangci-lint/cmd/golangci-lint@v1.46.2
+go install github.com/golangci/golangci-lint/cmd/golangci-lint@v1.48.0
 go install google.golang.org/protobuf/cmd/protoc-gen-go@v1.28
 go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@v1.2
 go install github.com/containerd/ttrpc/cmd/protoc-gen-go-ttrpc@944ef4a40df3446714a823207972b7d9858ffac5

script/setup/install-runc

@@ -22,6 +22,12 @@ set -eu -o pipefail
 
 script_dir="$(cd -- "$(dirname -- "$0")" > /dev/null 2>&1; pwd -P)"
 
+# e2e and Cirrus will fail with "sudo: command not found"
+SUDO=''
+if (( $EUID != 0 )); then
+    SUDO='sudo'
+fi
+
 function install_runc() {
 	# When updating runc-version, consider updating the runc module in go.mod as well
 	: "${RUNC_VERSION:=$(cat "${script_dir}/runc-version")}"
@@ -31,15 +37,15 @@ function install_runc() {
 	pushd "${TMPROOT}"/runc
 	git checkout "${RUNC_VERSION}"
 	make BUILDTAGS='seccomp' runc
-	make install
+	$SUDO make install
 	popd
 	rm -fR "${TMPROOT}"
 }
 
 function install_crun() {
 	: "${CRUN_VERSION:=$(cat "${script_dir}/crun-version")}"
-	curl -S -o /usr/local/sbin/runc -L https://github.com/containers/crun/releases/download/"${CRUN_VERSION}"/crun-"${CRUN_VERSION}"-linux-"$(go env GOARCH)"
-	chmod +x /usr/local/sbin/runc
+	$SUDO curl -S -o /usr/local/sbin/runc -L https://github.com/containers/crun/releases/download/"${CRUN_VERSION}"/crun-"${CRUN_VERSION}"-linux-"$(go env GOARCH)"
+	$SUDO chmod +x /usr/local/sbin/runc
 }
 
 : "${RUNC_FLAVOR:=runc}"

script/setup/install-seccomp

@@ -30,8 +30,8 @@ curl -fsSL "https://github.com/seccomp/libseccomp/releases/download/v${SECCOMP_V
 	cd "$SECCOMP_PATH"
 	./configure --prefix=/usr/local
 	make
-	make install
-	ldconfig
+	sudo make install
+	sudo ldconfig
 )
 
 rm -rf "$SECCOMP_PATH"

script/setup/prepare_env_windows.ps1

@@ -5,7 +5,7 @@
 # lived test environment.
 Set-MpPreference -DisableRealtimeMonitoring:$true
 
-$PACKAGES= @{ mingw = "10.2.0"; git = ""; golang = "1.18.5"; make = ""; nssm = "" }
+$PACKAGES= @{ mingw = "10.2.0"; git = ""; golang = "1.19"; make = ""; nssm = "" }
 
 Write-Host "Downloading chocolatey package"
 curl.exe -L "https://packages.chocolatey.org/chocolatey.0.10.15.nupkg" -o 'c:\choco.zip'

snapshots/devmapper/dmsetup/dmsetup.go

@@ -353,6 +353,7 @@ func BlockDeviceSize(path string) (int64, error) {
 }
 
 // DiscardBlocks discards all blocks for the given thin device
+//
 //	ported from https://github.com/moby/moby/blob/7b9275c0da707b030e62c96b679a976f31f929d3/pkg/devicemapper/devmapper.go#L416
 func DiscardBlocks(deviceName string) error {
 	inUse, err := isInUse(deviceName)
@@ -402,8 +403,10 @@ func tryGetUnixError(output string) (unix.Errno, bool) {
 }
 
 // dmsetup returns error messages in format:
+//
 //	device-mapper: message ioctl on <name> failed: File exists\n
 //	Command failed\n
+//
 // parseDmsetupError extracts text between "failed: " and "\n"
 func parseDmsetupError(output string) string {
 	lines := strings.SplitN(output, "\n", 2)

snapshots/devmapper/pool_device.go

@@ -484,7 +484,9 @@ func (p *PoolDevice) IsLoaded(deviceName string) bool {
 // GetUsage reports total size in bytes consumed by a thin-device.
 // It relies on the number of used blocks reported by 'dmsetup status'.
 // The output looks like:
+//
 //	device2: 0 204800 thin 17280 204799
+//
 // Where 17280 is the number of used sectors
 func (p *PoolDevice) GetUsage(deviceName string) (int64, error) {
 	status, err := dmsetup.Status(deviceName)

snapshots/snapshotter.go

@@ -167,7 +167,7 @@ type WalkFunc func(context.Context, Info) error
 //
 // We cover several examples below to demonstrate the utility of the snapshotter.
 //
-// Importing a Layer
+// # Importing a Layer
 //
 // To import a layer, we simply have the snapshotter provide a list of
 // mounts to be applied such that our dst will capture a changeset. We start
@@ -220,7 +220,7 @@ type WalkFunc func(context.Context, Info) error
 // Now, we have a layer in the snapshotter that can be accessed with the digest
 // provided during commit.
 //
-// Importing the Next Layer
+// # Importing the Next Layer
 //
 // Making a layer depend on the above is identical to the process described
 // above except that the parent is provided as parent when calling
@@ -231,7 +231,7 @@ type WalkFunc func(context.Context, Info) error
 // We then mount, apply and commit, as we did above. The new snapshot will be
 // based on the content of the previous one.
 //
-// Running a Container
+// # Running a Container
 //
 // To run a container, we simply provide snapshotter.Prepare() the committed image
 // snapshot as the parent. After mounting, the prepared path can

snapshots/testsuite/testsuite.go

@@ -559,6 +559,7 @@ func checkRemoveIntermediateSnapshot(ctx context.Context, t *testing.T, snapshot
 
 // baseTestSnapshots creates a base set of snapshots for tests, each snapshot is empty
 // Tests snapshots:
+//
 //	c1 - committed snapshot, no parent
 //	c2 - committed snapshot, c1 is parent
 //	a1 - active snapshot, c2 is parent