devmapper: add snapshotter config

Signed-off-by: Maksym Pavlenko <makpav@amazon.com>

snapshots/devmapper/config.go

@@ -0,0 +1,158 @@
+/*
+   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 devmapper
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/BurntSushi/toml"
+	"github.com/containerd/containerd/snapshots/devmapper/dmsetup"
+	"github.com/docker/go-units"
+	"github.com/hashicorp/go-multierror"
+	"github.com/pkg/errors"
+)
+
+const (
+	// See https://www.kernel.org/doc/Documentation/device-mapper/thin-provisioning.txt for details
+	dataBlockMinSize = 128
+	dataBlockMaxSize = 2097152
+)
+
+var (
+	errInvalidBlockSize      = errors.Errorf("block size should be between %d and %d", dataBlockMinSize, dataBlockMaxSize)
+	errInvalidBlockAlignment = errors.Errorf("block size should be multiple of %d sectors", dataBlockMinSize)
+)
+
+// Config represents device mapper configuration loaded from file.
+// Size units can be specified in human-readable string format (like "32KIB", "32GB", "32Tb")
+type Config struct {
+	// Device snapshotter root directory for metadata
+	RootPath string `toml:"root_path"`
+
+	// Name for 'thin-pool' device to be used by snapshotter (without /dev/mapper/ prefix)
+	PoolName string `toml:"pool_name"`
+
+	// Path to data volume to be used by thin-pool
+	DataDevice string `toml:"data_device"`
+
+	// Path to metadata volume to be used by thin-pool
+	MetadataDevice string `toml:"meta_device"`
+
+	// The size of allocation chunks in data file.
+	// Must be between 128 sectors (64KB) and 2097152 sectors (1GB) and a multiple of 128 sectors (64KB)
+	// Block size can't be changed after pool created.
+	// See https://www.kernel.org/doc/Documentation/device-mapper/thin-provisioning.txt
+	DataBlockSize        string `toml:"data_block_size"`
+	DataBlockSizeSectors uint32 `toml:"-"`
+
+	// Defines how much space to allocate when creating base image for container
+	BaseImageSize      string `toml:"base_image_size"`
+	BaseImageSizeBytes uint64 `toml:"-"`
+}
+
+// LoadConfig reads devmapper configuration file JSON format from disk
+func LoadConfig(path string) (*Config, error) {
+	if _, err := os.Stat(path); err != nil {
+		if os.IsNotExist(err) {
+			return nil, os.ErrNotExist
+		}
+
+		return nil, err
+	}
+
+	config := Config{}
+	if _, err := toml.DecodeFile(path, &config); err != nil {
+		return nil, errors.Wrapf(err, "failed to unmarshal data at '%s'", path)
+	}
+
+	if err := config.parse(); err != nil {
+		return nil, err
+	}
+
+	if err := config.Validate(); err != nil {
+		return nil, err
+	}
+
+	return &config, nil
+}
+
+func (c *Config) parse() error {
+	var result *multierror.Error
+
+	if c.DataBlockSize != "" {
+		if blockSize, err := units.RAMInBytes(c.DataBlockSize); err != nil {
+			result = multierror.Append(result, errors.Wrapf(err, "failed to parse data block size: %q", c.DataBlockSize))
+		} else {
+			c.DataBlockSizeSectors = uint32(blockSize / dmsetup.SectorSize)
+		}
+	}
+
+	if baseImageSize, err := units.RAMInBytes(c.BaseImageSize); err != nil {
+		result = multierror.Append(result, errors.Wrapf(err, "failed to parse base image size: %q", c.BaseImageSize))
+	} else {
+		c.BaseImageSizeBytes = uint64(baseImageSize)
+	}
+
+	return result.ErrorOrNil()
+}
+
+// Validate makes sure configuration fields are valid
+func (c *Config) Validate() error {
+	var result *multierror.Error
+
+	if c.PoolName == "" {
+		result = multierror.Append(result, fmt.Errorf("pool_name is required"))
+	}
+
+	if c.RootPath == "" {
+		result = multierror.Append(result, fmt.Errorf("root_path is required"))
+	}
+
+	if c.BaseImageSize == "" {
+		result = multierror.Append(result, fmt.Errorf("base_image_size is required"))
+	}
+
+	// The following fields are required only if we want to create or reload pool.
+	// Otherwise existing pool with 'PoolName' (prepared in advance) can be used by snapshotter.
+	if c.DataDevice != "" || c.MetadataDevice != "" || c.DataBlockSize != "" || c.DataBlockSizeSectors != 0 {
+		strChecks := []struct {
+			field string
+			name  string
+		}{
+			{c.DataDevice, "data_device"},
+			{c.MetadataDevice, "meta_device"},
+			{c.DataBlockSize, "data_block_size"},
+		}
+
+		for _, check := range strChecks {
+			if check.field == "" {
+				result = multierror.Append(result, errors.Errorf("%s is empty", check.name))
+			}
+		}
+
+		if c.DataBlockSizeSectors < dataBlockMinSize || c.DataBlockSizeSectors > dataBlockMaxSize {
+			result = multierror.Append(result, errInvalidBlockSize)
+		}
+
+		if c.DataBlockSizeSectors%dataBlockMinSize != 0 {
+			result = multierror.Append(result, errInvalidBlockAlignment)
+		}
+	}
+
+	return result.ErrorOrNil()
+}

snapshots/devmapper/config_test.go

@@ -0,0 +1,122 @@
+/*
+   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 devmapper
+
+import (
+	"io/ioutil"
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/BurntSushi/toml"
+	"github.com/hashicorp/go-multierror"
+	"gotest.tools/assert"
+	is "gotest.tools/assert/cmp"
+)
+
+func TestLoadConfig(t *testing.T) {
+	expected := Config{
+		RootPath:       "/tmp",
+		PoolName:       "test",
+		DataDevice:     "/dev/loop0",
+		MetadataDevice: "/dev/loop1",
+		DataBlockSize:  "1mb",
+		BaseImageSize:  "128Mb",
+	}
+
+	file, err := ioutil.TempFile("", "devmapper-config-")
+	assert.NilError(t, err)
+
+	encoder := toml.NewEncoder(file)
+	err = encoder.Encode(&expected)
+	assert.NilError(t, err)
+
+	defer func() {
+		err := file.Close()
+		assert.NilError(t, err)
+
+		err = os.Remove(file.Name())
+		assert.NilError(t, err)
+	}()
+
+	loaded, err := LoadConfig(file.Name())
+	assert.NilError(t, err)
+
+	assert.Equal(t, loaded.RootPath, expected.RootPath)
+	assert.Equal(t, loaded.PoolName, expected.PoolName)
+	assert.Equal(t, loaded.DataDevice, expected.DataDevice)
+	assert.Equal(t, loaded.MetadataDevice, expected.MetadataDevice)
+	assert.Equal(t, loaded.DataBlockSize, expected.DataBlockSize)
+	assert.Equal(t, loaded.BaseImageSize, expected.BaseImageSize)
+
+	assert.Assert(t, loaded.DataBlockSizeSectors == 1*1024*1024/512)
+	assert.Assert(t, loaded.BaseImageSizeBytes == 128*1024*1024)
+}
+
+func TestLoadConfigInvalidPath(t *testing.T) {
+	_, err := LoadConfig("")
+	assert.Equal(t, os.ErrNotExist, err)
+
+	_, err = LoadConfig("/dev/null")
+	assert.Assert(t, err != nil)
+}
+
+func TestParseInvalidData(t *testing.T) {
+	config := Config{
+		DataBlockSize: "x",
+		BaseImageSize: "y",
+	}
+
+	err := config.parse()
+	assert.Assert(t, err != nil)
+
+	multErr := (err).(*multierror.Error)
+	assert.Assert(t, is.Len(multErr.Errors, 2))
+
+	assert.Assert(t, strings.Contains(multErr.Errors[0].Error(), "failed to parse data block size: \"x\""))
+	assert.Assert(t, strings.Contains(multErr.Errors[1].Error(), "failed to parse base image size: \"y\""))
+}
+
+func TestFieldValidation(t *testing.T) {
+	config := &Config{DataBlockSizeSectors: 1}
+	err := config.Validate()
+	assert.Assert(t, err != nil)
+
+	multErr := (err).(*multierror.Error)
+	assert.Assert(t, is.Len(multErr.Errors, 8))
+
+	assert.Assert(t, multErr.Errors[0] != nil, "pool_name is empty")
+	assert.Assert(t, multErr.Errors[1] != nil, "root_path is empty")
+	assert.Assert(t, multErr.Errors[2] != nil, "base_image_size is empty")
+	assert.Assert(t, multErr.Errors[3] != nil, "data_device is empty")
+	assert.Assert(t, multErr.Errors[4] != nil, "meta_device is empty")
+	assert.Assert(t, multErr.Errors[5] != nil, "data_block_size is empty")
+
+	assert.Equal(t, multErr.Errors[6], errInvalidBlockSize)
+	assert.Equal(t, multErr.Errors[7], errInvalidBlockAlignment)
+}
+
+func TestExistingPoolFieldValidation(t *testing.T) {
+	config := &Config{
+		PoolName:      "test",
+		RootPath:      "test",
+		BaseImageSize: "10mb",
+	}
+
+	err := config.Validate()
+	assert.NilError(t, err)
+}