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devmapper: add losetup
Signed-off-by: Maksym Pavlenko <[email protected]>
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‎snapshots/devmapper/losetup/losetup.go‎

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/*
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Copyright The containerd Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package losetup
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import (
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"os/exec"
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"strings"
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"github.com/pkg/errors"
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)
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// FindAssociatedLoopDevices returns a list of loop devices attached to a given image
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func FindAssociatedLoopDevices(imagePath string) ([]string, error) {
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output, err := losetup("--list", "--output", "NAME", "--associated", imagePath)
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if err != nil {
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return nil, errors.Wrapf(err, "failed to get loop devices: '%s'", output)
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}
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if output == "" {
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return []string{}, nil
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}
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items := strings.Split(output, "\n")
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if len(items) <= 1 {
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return []string{}, nil
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}
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// Skip header with column names
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return items[1:], nil
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}
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// AttachLoopDevice finds first available loop device and associates it with an image.
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func AttachLoopDevice(imagePath string) (string, error) {
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return losetup("--find", "--show", imagePath)
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}
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// DetachLoopDevice detaches loop devices
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func DetachLoopDevice(loopDevice ...string) error {
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args := append([]string{"--detach"}, loopDevice...)
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_, err := losetup(args...)
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return err
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}
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// RemoveLoopDevicesAssociatedWithImage detaches all loop devices attached to a given sparse image
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func RemoveLoopDevicesAssociatedWithImage(imagePath string) error {
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loopDevices, err := FindAssociatedLoopDevices(imagePath)
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if err != nil {
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return err
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}
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for _, loopDevice := range loopDevices {
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if err = DetachLoopDevice(loopDevice); err != nil {
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return err
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}
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}
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return nil
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}
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// losetup is a wrapper around losetup command line tool
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func losetup(args ...string) (string, error) {
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data, err := exec.Command("losetup", args...).CombinedOutput()
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output := string(data)
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if err != nil {
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return "", errors.Wrapf(err, "losetup %s\nerror: %s\n", strings.Join(args, " "), output)
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}
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return strings.TrimSuffix(output, "\n"), err
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}

‎snapshots/devmapper/losetup/losetup_test.go‎

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/*
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Copyright The containerd Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package losetup
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import (
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"io/ioutil"
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"os"
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"testing"
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"github.com/containerd/containerd/pkg/testutil"
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"github.com/docker/go-units"
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"gotest.tools/assert"
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is "gotest.tools/assert/cmp"
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)
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func TestLosetup(t *testing.T) {
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testutil.RequiresRoot(t)
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var (
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imagePath = createSparseImage(t)
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loopDevice1 string
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loopDevice2 string
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)
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defer func() {
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err := os.Remove(imagePath)
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assert.NilError(t, err)
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}()
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t.Run("AttachLoopDevice", func(t *testing.T) {
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dev1, err := AttachLoopDevice(imagePath)
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assert.NilError(t, err)
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assert.Assert(t, dev1 != "")
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dev2, err := AttachLoopDevice(imagePath)
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assert.NilError(t, err)
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assert.Assert(t, dev2 != dev1, "should attach different loop device")
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loopDevice1 = dev1
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loopDevice2 = dev2
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})
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t.Run("AttachEmptyLoopDevice", func(t *testing.T) {
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_, err := AttachLoopDevice("")
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assert.Assert(t, err != nil, "shouldn't attach empty path")
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})
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t.Run("FindAssociatedLoopDevices", func(t *testing.T) {
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devices, err := FindAssociatedLoopDevices(imagePath)
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assert.NilError(t, err)
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assert.Assert(t, is.Len(devices, 2), "unexpected number of attached devices")
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assert.Assert(t, is.Contains(devices, loopDevice1))
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assert.Assert(t, is.Contains(devices, loopDevice2))
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})
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t.Run("FindAssociatedLoopDevicesForInvalidImage", func(t *testing.T) {
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devices, err := FindAssociatedLoopDevices("")
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assert.NilError(t, err)
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assert.Assert(t, is.Len(devices, 0))
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})
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t.Run("DetachLoopDevice", func(t *testing.T) {
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err := DetachLoopDevice(loopDevice2)
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assert.NilError(t, err, "failed to detach %q", loopDevice2)
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})
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t.Run("DetachEmptyDevice", func(t *testing.T) {
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err := DetachLoopDevice("")
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assert.Assert(t, err != nil, "shouldn't detach empty path")
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})
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t.Run("RemoveLoopDevicesAssociatedWithImage", func(t *testing.T) {
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err := RemoveLoopDevicesAssociatedWithImage(imagePath)
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assert.NilError(t, err)
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devices, err := FindAssociatedLoopDevices(imagePath)
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assert.NilError(t, err)
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assert.Assert(t, is.Len(devices, 0))
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})
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t.Run("RemoveLoopDevicesAssociatedWithInvalidImage", func(t *testing.T) {
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err := RemoveLoopDevicesAssociatedWithImage("")
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assert.NilError(t, err)
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})
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}
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func createSparseImage(t *testing.T) string {
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file, err := ioutil.TempFile("", "losetup-tests-")
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assert.NilError(t, err)
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size, err := units.RAMInBytes("16Mb")
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assert.NilError(t, err)
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err = file.Truncate(size)
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assert.NilError(t, err)
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err = file.Close()
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assert.NilError(t, err)
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return file.Name()
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}

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