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Merge pull request #5756 from Kern--/discard-blocks
Discard blocks when removing a thin device
2 parents f6fa3fd + f1d79d3 commit 3b7a3d5

7 files changed

Lines changed: 114 additions & 4 deletions

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‎snapshots/devmapper/README.md‎

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@@ -26,6 +26,7 @@ The following configuration flags are supported:
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should be the same as in `/dev/mapper/` directory
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* `base_image_size` - defines how much space to allocate when creating the base device
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* `async_remove` - flag to async remove device using snapshot GC's cleanup callback
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* `discard_blocks` - whether to discard blocks when removing a device. This is especially useful for returning disk space to the filesystem when using loopback devices.
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Pool name and base image size are required snapshotter parameters.
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@@ -93,6 +94,7 @@ cat << EOF
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pool_name = "${POOL_NAME}"
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root_path = "${DATA_DIR}"
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base_image_size = "10GB"
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discard_blocks = true
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EOF
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```
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‎snapshots/devmapper/blkdiscard/blkdiscard.go‎

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@@ -0,0 +1,41 @@
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// +build linux
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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 blkdiscard
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import "os/exec"
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// Version returns the output of "blkdiscard --version"
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func Version() (string, error) {
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return blkdiscard("--version")
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}
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// BlkDiscard discards all blocks of a device.
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// devicePath is expected to be a fully qualified path.
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// BlkDiscard expects the caller to verify that the device is not in use.
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func BlkDiscard(devicePath string) (string, error) {
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return blkdiscard(devicePath)
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}
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func blkdiscard(args ...string) (string, error) {
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output, err := exec.Command("blkdiscard", args...).CombinedOutput()
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if err != nil {
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return "", err
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}
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return string(output), nil
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}

‎snapshots/devmapper/config.go‎

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@@ -43,6 +43,9 @@ type Config struct {
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// Flag to async remove device using Cleanup() callback in snapshots GC
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AsyncRemove bool `toml:"async_remove"`
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// Whether to discard blocks when removing a thin device.
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DiscardBlocks bool `toml:"discard_blocks"`
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}
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// LoadConfig reads devmapper configuration file from disk in TOML format

‎snapshots/devmapper/dmsetup/dmsetup.go‎

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@@ -16,6 +16,8 @@
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limitations under the License.
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*/
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// Copyright 2012-2017 Docker, Inc.
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package dmsetup
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2123
import (
@@ -26,6 +28,7 @@ import (
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"strconv"
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"strings"
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blkdiscard "github.com/containerd/containerd/snapshots/devmapper/blkdiscard"
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"github.com/pkg/errors"
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"golang.org/x/sys/unix"
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)
@@ -37,6 +40,9 @@ const (
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SectorSize = 512
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)
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// ErrInUse represents an error mutating a device because it is in use elsewhere
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var ErrInUse = errors.New("device is in use")
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// DeviceInfo represents device info returned by "dmsetup info".
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// dmsetup(8) provides more information on each of these fields.
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type DeviceInfo struct {
@@ -345,6 +351,24 @@ func BlockDeviceSize(path string) (int64, error) {
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return size, nil
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}
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// DiscardBlocks discards all blocks for the given thin device
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// ported from https://github.com/moby/moby/blob/7b9275c0da707b030e62c96b679a976f31f929d3/pkg/devicemapper/devmapper.go#L416
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func DiscardBlocks(deviceName string) error {
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inUse, err := isInUse(deviceName)
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if err != nil {
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return err
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}
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if inUse {
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return ErrInUse
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}
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path := GetFullDevicePath(deviceName)
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_, err = blkdiscard.BlkDiscard(path)
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if err != nil {
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return err
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}
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return nil
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}
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func dmsetup(args ...string) (string, error) {
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data, err := exec.Command("dmsetup", args...).CombinedOutput()
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output := string(data)
@@ -406,3 +430,14 @@ func parseDmsetupError(output string) string {
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str = strings.ToLower(str)
407431
return str
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}
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func isInUse(deviceName string) (bool, error) {
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info, err := Info(deviceName)
436+
if err != nil {
437+
return true, err
438+
}
439+
if len(info) != 1 {
440+
return true, errors.New("could not get device info")
441+
}
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return info[0].OpenCount != 0, nil
443+
}

‎snapshots/devmapper/dmsetup/dmsetup_test.go‎

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@@ -83,6 +83,7 @@ func TestDMSetup(t *testing.T) {
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t.Run("ActivateDevice", testActivateDevice)
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t.Run("DeviceStatus", testDeviceStatus)
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t.Run("SuspendResumeDevice", testSuspendResumeDevice)
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t.Run("DiscardBlocks", testDiscardBlocks)
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t.Run("RemoveDevice", testRemoveDevice)
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t.Run("RemovePool", func(t *testing.T) {
@@ -169,6 +170,11 @@ func testSuspendResumeDevice(t *testing.T) {
169170
assert.NilError(t, err)
170171
}
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173+
func testDiscardBlocks(t *testing.T) {
174+
err := DiscardBlocks(testDeviceName)
175+
assert.NilError(t, err, "failed to discard blocks")
176+
}
177+
172178
func testRemoveDevice(t *testing.T) {
173179
err := RemoveDevice(testPoolName)
174180
assert.Assert(t, err == unix.EBUSY, "removing thin-pool with dependencies shouldn't be allowed")

‎snapshots/devmapper/pool_device.go‎

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@@ -29,13 +29,15 @@ import (
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"golang.org/x/sys/unix"
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3131
"github.com/containerd/containerd/log"
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blkdiscard "github.com/containerd/containerd/snapshots/devmapper/blkdiscard"
3233
"github.com/containerd/containerd/snapshots/devmapper/dmsetup"
3334
)
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3536
// PoolDevice ties together data and metadata volumes, represents thin-pool and manages volumes, snapshots and device ids.
3637
type PoolDevice struct {
37-
poolName string
38-
metadata *PoolMetadata
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poolName string
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metadata *PoolMetadata
40+
discardBlocks bool
3941
}
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4143
// NewPoolDevice creates new thin-pool from existing data and metadata volumes.
@@ -51,6 +53,15 @@ func NewPoolDevice(ctx context.Context, config *Config) (*PoolDevice, error) {
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5254
log.G(ctx).Infof("using dmsetup:\n%s", version)
5355

56+
if config.DiscardBlocks {
57+
blkdiscardVersion, err := blkdiscard.Version()
58+
if err != nil {
59+
log.G(ctx).Error("blkdiscard is not available")
60+
return nil, err
61+
}
62+
log.G(ctx).Infof("using blkdiscard:\n%s", blkdiscardVersion)
63+
}
64+
5465
dbpath := filepath.Join(config.RootPath, config.PoolName+".db")
5566
poolMetaStore, err := NewPoolMetadata(dbpath)
5667
if err != nil {
@@ -64,8 +75,9 @@ func NewPoolDevice(ctx context.Context, config *Config) (*PoolDevice, error) {
6475
}
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6677
poolDevice := &PoolDevice{
67-
poolName: config.PoolName,
68-
metadata: poolMetaStore,
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poolName: config.PoolName,
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metadata: poolMetaStore,
80+
discardBlocks: config.DiscardBlocks,
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}
7082

7183
if err := poolDevice.ensureDeviceStates(ctx); err != nil {
@@ -422,6 +434,16 @@ func (p *PoolDevice) DeactivateDevice(ctx context.Context, deviceName string, de
422434

423435
if err := p.transition(ctx, deviceName, Deactivating, Deactivated, func() error {
424436
return retry(ctx, func() error {
437+
if !deferred && p.discardBlocks {
438+
err := dmsetup.DiscardBlocks(deviceName)
439+
if err != nil {
440+
if err == dmsetup.ErrInUse {
441+
log.G(ctx).Warnf("device %q is in use, skipping blkdiscard", deviceName)
442+
} else {
443+
return err
444+
}
445+
}
446+
}
425447
if err := dmsetup.RemoveDevice(deviceName, opts...); err != nil {
426448
return errors.Wrap(err, "failed to deactivate device")
427449
}

‎snapshots/devmapper/pool_device_test.go‎

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@@ -85,6 +85,7 @@ func TestPoolDevice(t *testing.T) {
8585
RootPath: tempDir,
8686
BaseImageSize: "16mb",
8787
BaseImageSizeBytes: 16 * 1024 * 1024,
88+
DiscardBlocks: true,
8889
}
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pool, err := NewPoolDevice(ctx, config)

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