Merge branch 'add-file-locks' into 'main'

Lock the cache dir for doing operations

Closes #11

See merge request bootc-org/podman-bootc-cli!62

Author: ckyrouac

cmd/list.go

@@ -1,14 +1,15 @@
 package cmd
 
 import (
-	"github.com/sirupsen/logrus"
 	"os"
 
 	"gitlab.com/bootc-org/podman-bootc/pkg/config"
 	"gitlab.com/bootc-org/podman-bootc/pkg/user"
+	"gitlab.com/bootc-org/podman-bootc/pkg/utils"
 	"gitlab.com/bootc-org/podman-bootc/pkg/vm"
 
 	"github.com/containers/common/pkg/report"
+	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 )
 
@@ -83,13 +84,20 @@ func getVMInfo(user user.User, libvirtUri string, imageId string) (*vm.BootcVMCo
 		ImageID:    imageId,
 		User:       user,
 		LibvirtUri: libvirtUri,
+		Locking:    utils.Shared,
 	})
 
 	if err != nil {
 		return nil, err
 	}
 
-	defer bootcVM.CloseConnection()
+	// Let's be explicit instead of relying on the defer exec order
+	defer func() {
+		bootcVM.CloseConnection()
+		if err := bootcVM.Unlock(); err != nil {
+			logrus.Warningf("unable to unlock VM %s: %v", imageId, err)
+		}
+	}()
 
 	cfg, err := bootcVM.GetConfig()
 	if err != nil {

cmd/rm.go

@@ -6,6 +6,7 @@ import (
 
 	"gitlab.com/bootc-org/podman-bootc/pkg/config"
 	"gitlab.com/bootc-org/podman-bootc/pkg/user"
+	"gitlab.com/bootc-org/podman-bootc/pkg/utils"
 	"gitlab.com/bootc-org/podman-bootc/pkg/vm"
 
 	"github.com/sirupsen/logrus"
@@ -60,12 +61,19 @@ func prune(id string) error {
 		ImageID:    id,
 		LibvirtUri: config.LibvirtUri,
 		User:       user,
+		Locking:    utils.Exclusive,
 	})
 	if err != nil {
 		return fmt.Errorf("unable to get VM %s: %v", id, err)
 	}
 
-	defer bootcVM.CloseConnection()
+	// Let's be explicit instead of relying on the defer exec order
+	defer func() {
+		bootcVM.CloseConnection()
+		if err := bootcVM.Unlock(); err != nil {
+			logrus.Warningf("unable to unlock VM %s: %v", id, err)
+		}
+	}()
 
 	if force {
 		err := forceKillVM(bootcVM)

cmd/run.go

@@ -116,13 +116,20 @@ func doRun(flags *cobra.Command, args []string) error {
 		ImageID:    bootcDisk.GetImageId(),
 		User:       user,
 		LibvirtUri: config.LibvirtUri,
+		Locking:    utils.Shared,
 	})
 
 	if err != nil {
 		return fmt.Errorf("unable to initialize VM: %w", err)
 	}
 
-	defer bootcVM.CloseConnection()
+	// Let's be explicit instead of relying on the defer exec order
+	defer func() {
+		bootcVM.CloseConnection()
+		if err := bootcVM.Unlock(); err != nil {
+			logrus.Warningf("unable to unlock VM %s: %v", bootcDisk.GetImageId(), err)
+		}
+	}()
 
 	cmd := args[1:]
 	err = bootcVM.Run(vm.RunVMParameters{

cmd/ssh.go

@@ -6,6 +6,7 @@ import (
 	"gitlab.com/bootc-org/podman-bootc/pkg/utils"
 	"gitlab.com/bootc-org/podman-bootc/pkg/vm"
 
+	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 )
 
@@ -35,13 +36,20 @@ func doSsh(_ *cobra.Command, args []string) error {
 		ImageID:    id,
 		User:       user,
 		LibvirtUri: config.LibvirtUri,
+		Locking:    utils.Shared,
 	})
 
 	if err != nil {
 		return err
 	}
 
-	defer vm.CloseConnection()
+	// Let's be explicit instead of relying on the defer exec order
+	defer func() {
+		vm.CloseConnection()
+		if err := vm.Unlock(); err != nil {
+			logrus.Warningf("unable to unlock VM %s: %v", id, err)
+		}
+	}()
 
 	err = vm.SetUser(sshUser)
 	if err != nil {

cmd/stop.go

@@ -3,8 +3,10 @@ package cmd
 import (
 	"gitlab.com/bootc-org/podman-bootc/pkg/config"
 	"gitlab.com/bootc-org/podman-bootc/pkg/user"
+	"gitlab.com/bootc-org/podman-bootc/pkg/utils"
 	"gitlab.com/bootc-org/podman-bootc/pkg/vm"
 
+	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 )
 
@@ -31,10 +33,19 @@ func doStop(_ *cobra.Command, args []string) (err error) {
 		ImageID:    id,
 		LibvirtUri: config.LibvirtUri,
 		User:       user,
+		Locking:    utils.Exclusive,
 	})
 	if err != nil {
 		return err
 	}
-	defer bootcVM.CloseConnection()
+
+	// Let's be explicit instead of relying on the defer exec order
+	defer func() {
+		bootcVM.CloseConnection()
+		if err := bootcVM.Unlock(); err != nil {
+			logrus.Warningf("unable to unlock VM %s: %v", id, err)
+		}
+	}()
+
 	return bootcVM.Delete()
 }

go.mod

@@ -7,6 +7,7 @@ require (
 	github.com/containers/common v0.58.1
 	github.com/containers/podman/v5 v5.0.1
 	github.com/docker/go-units v0.5.0
+	github.com/gofrs/flock v0.8.1
 	github.com/onsi/ginkgo/v2 v2.17.1
 	github.com/onsi/gomega v1.32.0
 	github.com/opencontainers/runtime-spec v1.2.0

go.sum

@@ -229,6 +229,8 @@ github.com/goccy/go-json v0.10.2/go.mod h1:6MelG93GURQebXPDq3khkgXZkazVtN9CRI+MG
 github.com/godbus/dbus/v5 v5.1.0/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
 github.com/godbus/dbus/v5 v5.1.1-0.20230522191255-76236955d466 h1:sQspH8M4niEijh3PFscJRLDnkL547IeP7kpPe3uUhEg=
 github.com/godbus/dbus/v5 v5.1.1-0.20230522191255-76236955d466/go.mod h1:ZiQxhyQ+bbbfxUKVvjfO498oPYvtYhZzycal3G/NHmU=
+github.com/gofrs/flock v0.8.1 h1:+gYjHKf32LDeiEEFhQaotPbLuUXjY5ZqxKgXy7n59aw=
+github.com/gofrs/flock v0.8.1/go.mod h1:F1TvTiK9OcQqauNUHlbJvyl9Qa1QvF/gOUDKA14jxHU=
 github.com/gogo/protobuf v1.3.2 h1:Ov1cvc58UF3b5XjBnZv7+opcTcQFZebYjWzi34vdm4Q=
 github.com/gogo/protobuf v1.3.2/go.mod h1:P1XiOD3dCwIKUDQYPy72D8LYyHL2YPYrpS2s69NZV8Q=
 github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=

pkg/bootc/bootc_disk.go

@@ -13,6 +13,7 @@ import (
 
 	"gitlab.com/bootc-org/podman-bootc/pkg/config"
 	"gitlab.com/bootc-org/podman-bootc/pkg/user"
+	"gitlab.com/bootc-org/podman-bootc/pkg/utils"
 
 	"github.com/containers/podman/v5/pkg/bindings/containers"
 	"github.com/containers/podman/v5/pkg/bindings/images"
@@ -103,6 +104,27 @@ func (p *BootcDisk) Install(quiet bool) (err error) {
 		return
 	}
 
+	// Create VM cache dir; one per oci bootc image
+	p.Directory = filepath.Join(p.User.CacheDir(), p.ImageId)
+	lock := utils.NewCacheLock(p.User.RunDir(), p.Directory)
+	locked, err := lock.TryLock(utils.Exclusive)
+	if err != nil {
+		return fmt.Errorf("error locking the VM cache path: %w", err)
+	}
+	if !locked {
+		return fmt.Errorf("unable to lock the VM cache path")
+	}
+
+	defer func() {
+		if err := lock.Unlock(); err != nil {
+			logrus.Errorf("unable to unlock VM %s: %v", p.ImageId, err)
+		}
+	}()
+
+	if err := os.MkdirAll(p.Directory, os.ModePerm); err != nil {
+		return fmt.Errorf("error while making bootc disk directory: %w", err)
+	}
+
 	err = p.getOrInstallImageToDisk(quiet)
 	if err != nil {
 		return
@@ -246,12 +268,6 @@ func (p *BootcDisk) pullImage() (err error) {
 	p.ImageId = imageId
 	p.RepoTag = image.RepoTags[0]
 
-	// Create VM cache dir; one per oci bootc image
-	p.Directory = filepath.Join(p.User.CacheDir(), imageId)
-	if err := os.MkdirAll(p.Directory, os.ModePerm); err != nil {
-		return fmt.Errorf("error while making bootc disk directory: %w", err)
-	}
-
 	return
 }
 

pkg/utils/locks.go

@@ -0,0 +1,41 @@
+package utils
+
+import (
+	"path/filepath"
+
+	"github.com/gofrs/flock"
+)
+
+type AccessMode uint
+
+const (
+	Exclusive AccessMode = iota
+	Shared
+)
+
+type CacheLock struct {
+	inner *flock.Flock
+}
+
+// NewCacheLock  returns a new instance of *CacheLock. It takes the path to the VM cache dir.
+func NewCacheLock(lockDir, cacheDir string) CacheLock {
+	imageLongID := filepath.Base(cacheDir)
+	cacheDirLockFile := filepath.Join(lockDir, imageLongID+".lock")
+	return CacheLock{inner: flock.New(cacheDirLockFile)}
+}
+
+// TryLock takes an exclusive or shared lock, based on the parameter mode.
+// The lock is non-blocking, if we are unable to lock the cache directory,
+// the function will return false instead of waiting for the lock.
+func (l CacheLock) TryLock(mode AccessMode) (bool, error) {
+	if mode == Exclusive {
+		return l.inner.TryLock()
+	} else {
+		return l.inner.TryRLock()
+	}
+}
+
+// Unlock unlocks the cache lock.
+func (l CacheLock) Unlock() error {
+	return l.inner.Unlock()
+}

pkg/vm/vm.go

@@ -3,6 +3,7 @@ package vm
 import (
 	"encoding/base64"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"os"
 	"os/exec"
@@ -14,12 +15,15 @@ import (
 	"gitlab.com/bootc-org/podman-bootc/pkg/bootc"
 	"gitlab.com/bootc-org/podman-bootc/pkg/config"
 	"gitlab.com/bootc-org/podman-bootc/pkg/user"
+	"gitlab.com/bootc-org/podman-bootc/pkg/utils"
 
 	"github.com/docker/go-units"
 	"github.com/sirupsen/logrus"
 	"golang.org/x/crypto/ssh"
 )
 
+var ErrVMInUse = errors.New("VM already in use")
+
 // GetVMCachePath returns the path to the VM cache directory
 func GetVMCachePath(imageId string, user user.User) (path string, err error) {
 	files, err := os.ReadDir(user.CacheDir())
@@ -45,6 +49,7 @@ type NewVMParameters struct {
 	ImageID    string
 	User       user.User //user who is running the podman bootc command
 	LibvirtUri string    //linux only
+	Locking    utils.AccessMode
 }
 
 type RunVMParameters struct {
@@ -71,6 +76,7 @@ type BootcVM interface {
 	GetConfig() (*BootcVMConfig, error)
 	CloseConnection()
 	PrintConsole() error
+	Unlock() error
 }
 
 type BootcVMCommon struct {
@@ -92,6 +98,7 @@ type BootcVMCommon struct {
 	cloudInitDir  string
 	cloudInitArgs string
 	bootcDisk     bootc.BootcDisk
+	cacheDirLock  utils.CacheLock
 }
 
 type BootcVMConfig struct {
@@ -274,3 +281,31 @@ func (b *BootcVMCommon) tmpFileInjectSshKeyEnc() (string, error) {
 	tmpFileCmdEnc := base64.StdEncoding.EncodeToString([]byte(tmpFileCmd))
 	return tmpFileCmdEnc, nil
 }
+
+func lockVM(params NewVMParameters, cacheDir string) (utils.CacheLock, error) {
+	lock := utils.NewCacheLock(params.User.RunDir(), cacheDir)
+	locked, err := lock.TryLock(params.Locking)
+	if err != nil {
+		return lock, fmt.Errorf("unable to lock the VM cache path: %w", err)
+	}
+
+	if !locked {
+		return lock, ErrVMInUse
+	}
+
+	cacheDirExists, err := utils.FileExists(cacheDir)
+	if err != nil {
+		if err := lock.Unlock(); err != nil {
+			logrus.Debugf("unlock failed: %v", err)
+		}
+		return lock, fmt.Errorf("unable to check cache path: %w", err)
+	}
+	if !cacheDirExists {
+		if err := lock.Unlock(); err != nil {
+			logrus.Debugf("unlock failed: %v", err)
+		}
+		return lock, fmt.Errorf("'%s' does not exists", params.ImageID)
+	}
+
+	return lock, nil
+}