tests/*: introduce go-dmflakey

This commit is to add go-binding for go-dmflakey. It's used to simulate
powerfailure with common filesystems.

Signed-off-by: Wei Fu <fuweid89@gmail.com>

.github/workflows/failpoint_test.yaml

@@ -15,5 +15,6 @@ jobs:
         with:
           go-version: ${{ steps.goversion.outputs.goversion }}
       - run: |
+          sudo make root-test
           make gofail-enable
           make test-failpoint

Makefile

@@ -81,3 +81,6 @@ test-failpoint:
 	@echo "[failpoint] array freelist test"
 	BBOLT_VERIFY=all TEST_FREELIST_TYPE=array go test -v ${TESTFLAGS} -timeout 30m ./tests/failpoint
 
+.PHONY: root-test # run tests that require root
+root-test:
+	go test -v ${TESTFLAGS} ./tests/dmflakey -test.root

tests/dmflakey/dmflakey.go

@@ -0,0 +1,322 @@
+//go:build linux
+
+package dmflakey
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"golang.org/x/sys/unix"
+)
+
+type featCfg struct {
+	// SyncFS attempts to synchronize filesystem before inject failure.
+	syncFS bool
+	// interval is used to determine the up time for feature.
+	//
+	// For AllowWrites, it means that the device is available for `interval` seconds.
+	// For Other features, the device exhibits unreliable behaviour for
+	// `interval` seconds.
+	interval time.Duration
+}
+
+// Default values.
+const (
+	// defaultImgSize is the default size for filesystem image.
+	defaultImgSize int64 = 1024 * 1024 * 1024 * 10 // 10 GiB
+	// defaultInterval is the default interval for the up time of feature.
+	defaultInterval = 2 * time.Minute
+)
+
+// defaultFeatCfg is the default setting for flakey feature.
+var defaultFeatCfg = featCfg{interval: defaultInterval}
+
+// FeatOpt is used to configure failure feature.
+type FeatOpt func(*featCfg)
+
+// WithIntervalFeatOpt updates the up time for the feature.
+func WithIntervalFeatOpt(interval time.Duration) FeatOpt {
+	return func(cfg *featCfg) {
+		cfg.interval = interval
+	}
+}
+
+// WithSyncFSFeatOpt is to determine if the caller wants to synchronize
+// filesystem before inject failure.
+func WithSyncFSFeatOpt(syncFS bool) FeatOpt {
+	return func(cfg *featCfg) {
+		cfg.syncFS = syncFS
+	}
+}
+
+// Flakey is to inject failure into device.
+type Flakey interface {
+	// DevicePath returns the flakey device path.
+	DevicePath() string
+
+	// Filesystem returns filesystem's type.
+	Filesystem() FSType
+
+	// AllowWrites allows write I/O.
+	AllowWrites(opts ...FeatOpt) error
+
+	// DropWrites drops all write I/O silently.
+	DropWrites(opts ...FeatOpt) error
+
+	// ErrorWrites drops all write I/O and returns error.
+	ErrorWrites(opts ...FeatOpt) error
+
+	// Teardown releases the flakey device.
+	Teardown() error
+}
+
+// FSType represents the filesystem name.
+type FSType string
+
+// Supported filesystems.
+const (
+	FSTypeEXT4 FSType = "ext4"
+	FSTypeXFS  FSType = "xfs"
+)
+
+// InitFlakey creates an filesystem on a loopback device and returns Flakey on it.
+//
+// The device-mapper device will be /dev/mapper/$flakeyDevice. And the filesystem
+// image will be created at $dataStorePath/$flakeyDevice.img. By default, the
+// device is available for 2 minutes and size is 10 GiB.
+func InitFlakey(flakeyDevice, dataStorePath string, fsType FSType) (_ Flakey, retErr error) {
+	imgPath := filepath.Join(dataStorePath, fmt.Sprintf("%s.img", flakeyDevice))
+	if err := createEmptyFSImage(imgPath, fsType); err != nil {
+		return nil, err
+	}
+	defer func() {
+		if retErr != nil {
+			os.RemoveAll(imgPath)
+		}
+	}()
+
+	loopDevice, err := attachToLoopDevice(imgPath)
+	if err != nil {
+		return nil, err
+	}
+	defer func() {
+		if retErr != nil {
+			_ = detachLoopDevice(loopDevice)
+		}
+	}()
+
+	imgSize, err := getBlkSize(loopDevice)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := newFlakeyDevice(flakeyDevice, loopDevice, defaultInterval); err != nil {
+		return nil, err
+	}
+
+	return &flakey{
+		fsType:  fsType,
+		imgPath: imgPath,
+		imgSize: imgSize,
+
+		loopDevice:   loopDevice,
+		flakeyDevice: flakeyDevice,
+	}, nil
+}
+
+type flakey struct {
+	fsType  FSType
+	imgPath string
+	imgSize int64
+
+	loopDevice   string
+	flakeyDevice string
+}
+
+// DevicePath returns the flakey device path.
+func (f *flakey) DevicePath() string {
+	return fmt.Sprintf("/dev/mapper/%s", f.flakeyDevice)
+}
+
+// Filesystem returns filesystem's type.
+func (f *flakey) Filesystem() FSType {
+	return f.fsType
+}
+
+// AllowWrites allows write I/O.
+func (f *flakey) AllowWrites(opts ...FeatOpt) error {
+	var o = defaultFeatCfg
+	for _, opt := range opts {
+		opt(&o)
+	}
+
+	// NOTE: Table parameters
+	//
+	// 0 imgSize flakey <dev path> <offset> <up interval> <down interval> [<num_features> [<feature arguments>]]
+	//
+	// Mandatory parameters:
+	//
+	//  <dev path>: Full pathname to the underlying block-device, or a "major:minor" device-number.
+	//  <offset>: Starting sector within the device.
+	//  <up interval>: Number of seconds device is available.
+	//  <down interval>: Number of seconds device returns errors.
+	//
+	// Optional:
+	//
+	// If no feature parameters are present, during the periods of unreliability, all I/O returns errors.
+	//
+	// For AllowWrites, the device will handle data correctly in `interval` seconds.
+	//
+	// REF: https://docs.kernel.org/admin-guide/device-mapper/dm-flakey.html.
+	table := fmt.Sprintf("0 %d flakey %s 0 %d 0",
+		f.imgSize, f.loopDevice, int(o.interval.Seconds()))
+
+	return reloadFlakeyDevice(f.flakeyDevice, o.syncFS, table)
+}
+
+// DropWrites drops all write I/O silently.
+func (f *flakey) DropWrites(opts ...FeatOpt) error {
+	var o = defaultFeatCfg
+	for _, opt := range opts {
+		opt(&o)
+	}
+
+	// NOTE: Table parameters
+	//
+	// 0 imgSize flakey <dev path> <offset> <up interval> <down interval> [<num_features> [<feature arguments>]]
+	//
+	// Mandatory parameters:
+	//
+	//  <dev path>: Full pathname to the underlying block-device, or a "major:minor" device-number.
+	//  <offset>: Starting sector within the device.
+	//  <up interval>: Number of seconds device is available.
+	//  <down interval>: Number of seconds device returns errors.
+	//
+	// Optional:
+	//
+	// <num_features>: How many arguments (length of <feature_arguments>)
+	//
+	// For DropWrites,
+	//
+	// num_features: 1 (there is only one argument)
+	// feature_arguments: drop_writes
+	//
+	// The Device will drop all the writes into disk in `interval` seconds.
+	// Read I/O is handled correctly.
+	//
+	// For example, the application calls fsync, all the dirty pages will
+	// be flushed into disk ideally. But during DropWrites, device will
+	// ignore all the data and return successfully. It can be used to
+	// simulate data-loss after power failure.
+	//
+	// REF: https://docs.kernel.org/admin-guide/device-mapper/dm-flakey.html.
+	table := fmt.Sprintf("0 %d flakey %s 0 0 %d 1 drop_writes",
+		f.imgSize, f.loopDevice, int(o.interval.Seconds()))
+
+	return reloadFlakeyDevice(f.flakeyDevice, o.syncFS, table)
+}
+
+// ErrorWrites drops all write I/O and returns error.
+func (f *flakey) ErrorWrites(opts ...FeatOpt) error {
+	var o = defaultFeatCfg
+	for _, opt := range opts {
+		opt(&o)
+	}
+
+	// NOTE: Table parameters
+	//
+	// 0 imgSize flakey <dev path> <offset> <up interval> <down interval> [<num_features> [<feature arguments>]]
+	//
+	// Mandatory parameters:
+	//
+	//  <dev path>: Full pathname to the underlying block-device, or a "major:minor" device-number.
+	//  <offset>: Starting sector within the device.
+	//  <up interval>: Number of seconds device is available.
+	//  <down interval>: Number of seconds device returns errors.
+	//
+	// Optional:
+	//
+	// <num_features>: How many arguments (length of <feature_arguments>)
+	//
+	// For ErrorWrites,
+	//
+	// num_features: 1 (there is only one argument)
+	// feature_arguments: error_writes
+	//
+	// The Device will drop all the writes into disk in `interval` seconds
+	// and return failure to caller. Read I/O is handled correctly.
+	//
+	// REF: https://docs.kernel.org/admin-guide/device-mapper/dm-flakey.html.
+	table := fmt.Sprintf("0 %d flakey %s 0 0 %d 1 error_writes",
+		f.imgSize, f.loopDevice, int(o.interval.Seconds()))
+
+	return reloadFlakeyDevice(f.flakeyDevice, o.syncFS, table)
+}
+
+// Teardown releases the flakey device.
+func (f *flakey) Teardown() error {
+	if err := deleteFlakeyDevice(f.flakeyDevice); err != nil {
+		if !strings.Contains(err.Error(), "No such device or address") {
+			return err
+		}
+	}
+	if err := detachLoopDevice(f.loopDevice); err != nil {
+		if !errors.Is(err, unix.ENXIO) {
+			return err
+		}
+	}
+	return os.RemoveAll(f.imgPath)
+}
+
+// createEmptyFSImage creates empty filesystem on dataStorePath folder with
+// default size - 10 GiB.
+func createEmptyFSImage(imgPath string, fsType FSType) error {
+	if err := validateFSType(fsType); err != nil {
+		return err
+	}
+
+	mkfs, err := exec.LookPath(fmt.Sprintf("mkfs.%s", fsType))
+	if err != nil {
+		return fmt.Errorf("failed to ensure mkfs.%s: %w", fsType, err)
+	}
+
+	if _, err := os.Stat(imgPath); err == nil {
+		return fmt.Errorf("failed to create image because %s already exists", imgPath)
+	}
+
+	f, err := os.Create(imgPath)
+	if err != nil {
+		return fmt.Errorf("failed to create image %s: %w", imgPath, err)
+	}
+
+	if err = func() error {
+		defer f.Close()
+
+		return f.Truncate(defaultImgSize)
+	}(); err != nil {
+		return fmt.Errorf("failed to truncate image %s with %v bytes: %w",
+			imgPath, defaultImgSize, err)
+	}
+
+	output, err := exec.Command(mkfs, imgPath).CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("failed to mkfs.%s on %s (out: %s): %w",
+			fsType, imgPath, string(output), err)
+	}
+	return nil
+}
+
+// validateFSType validates the fs type input.
+func validateFSType(fsType FSType) error {
+	switch fsType {
+	case FSTypeEXT4, FSTypeXFS:
+		return nil
+	default:
+		return fmt.Errorf("unsupported filesystem %s", fsType)
+	}
+}