Implement mount from image

Signed-off-by: Laurent Goderre <laurent.goderre@docker.com>
moby · Oct 30, 2024 · fd65589 · fd65589
1 parent 8eba9bf
commit fd65589
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Showing 8 changed files with 110 additions and 23 deletions.
diff --git a/api/types/mount/mount.go b/api/types/mount/mount.go
@@ -19,6 +19,8 @@ const (
 	TypeNamedPipe Type = "npipe"
 	// TypeCluster is the type for Swarm Cluster Volumes.
 	TypeCluster Type = "cluster"
+	// TypeImage is the type for mounting another image's filesystem
+	TypeImage Type = "image"
 )
 
 // Mount represents a mount (volume).

diff --git a/daemon/containerd/service.go b/daemon/containerd/service.go
@@ -20,6 +20,7 @@ import (
 	dimages "github.com/docker/docker/daemon/images"
 	"github.com/docker/docker/daemon/snapshotter"
 	"github.com/docker/docker/errdefs"
+	"github.com/docker/docker/image"
 	"github.com/docker/docker/layer"
 	"github.com/docker/docker/pkg/idtools"
 	"github.com/docker/docker/registry"
@@ -115,6 +116,10 @@ func (i *ImageService) CreateLayer(container *container.Container, initFunc laye
 	return nil, errdefs.NotImplemented(errdefs.NotImplemented(errors.New("not implemented")))
 }
 
+func (i *ImageService) CreateLayerFromImage(img *image.Image, layerName string, rwLayerOpts *layer.CreateRWLayerOpts) (layer.RWLayer, error) {
+	return nil, errdefs.NotImplemented(errdefs.NotImplemented(errors.New("not implemented")))
+}
+
 // LayerStoreStatus returns the status for each layer store
 // called from info.go
 func (i *ImageService) LayerStoreStatus() [][2]string {
@@ -124,6 +129,12 @@ func (i *ImageService) LayerStoreStatus() [][2]string {
 	}
 }
 
+// GetLayerByID returns a layer by ID
+// called from daemon.go Daemon.restore().
+func (i *ImageService) GetLayerByID(cid string) (layer.RWLayer, error) {
+	return nil, errdefs.NotImplemented(errors.New("not implemented"))
+}
+
 // GetLayerMountID returns the mount ID for a layer
 // called from daemon.go Daemon.Shutdown(), and Daemon.Cleanup() (cleanup is actually containerCleanup)
 // TODO: needs to be refactored to Unmount (see callers), or removed and replaced with GetLayerByID

diff --git a/daemon/image_service.go b/daemon/image_service.go
@@ -54,7 +54,9 @@ type ImageService interface {
 
 	GetImageAndReleasableLayer(ctx context.Context, refOrID string, opts backend.GetImageAndLayerOptions) (builder.Image, builder.ROLayer, error)
 	CreateLayer(container *container.Container, initFunc layer.MountInit) (layer.RWLayer, error)
+	CreateLayerFromImage(img *image.Image, layerName string, rwLayerOpts *layer.CreateRWLayerOpts) (layer.RWLayer, error)
 	LayerStoreStatus() [][2]string
+	GetLayerByID(cid string) (layer.RWLayer, error)
 	GetLayerMountID(cid string) (string, error)
 	ReleaseLayer(rwlayer layer.RWLayer) error
 	LayerDiskUsage(ctx context.Context) (int64, error)

diff --git a/daemon/images/service.go b/daemon/images/service.go
@@ -118,13 +118,13 @@ func (i *ImageService) Children(_ context.Context, id image.ID) ([]image.ID, err
 // called from create.go
 // TODO: accept an opt struct instead of container?
 func (i *ImageService) CreateLayer(container *container.Container, initFunc layer.MountInit) (layer.RWLayer, error) {
-	var layerID layer.ChainID
+	var img *image.Image
 	if container.ImageID != "" {
-		img, err := i.imageStore.Get(container.ImageID)
+		i, err := i.imageStore.Get(container.ImageID)
 		if err != nil {
 			return nil, err
 		}
-		layerID = img.RootFS.ChainID()
+		img = i
 	}
 
 	rwLayerOpts := &layer.CreateRWLayerOpts{
@@ -133,7 +133,15 @@ func (i *ImageService) CreateLayer(container *container.Container, initFunc laye
 		StorageOpt: container.HostConfig.StorageOpt,
 	}
 
-	return i.layerStore.CreateRWLayer(container.ID, layerID, rwLayerOpts)
+	return i.CreateLayerFromImage(img, container.ID, rwLayerOpts)
+}
+
+// CreateLayerFromImage creates a file system from an arbitrary image
+// Used to mount an image inside another
+func (i *ImageService) CreateLayerFromImage(img *image.Image, layerName string, rwLayerOpts *layer.CreateRWLayerOpts) (layer.RWLayer, error) {
+	layerID := img.RootFS.ChainID()
+
+	return i.layerStore.CreateRWLayer(layerName, layerID, rwLayerOpts)
 }
 
 // GetLayerByID returns a layer by ID

diff --git a/daemon/mounts.go b/daemon/mounts.go
@@ -38,28 +38,46 @@ func (daemon *Daemon) removeMountPoints(container *container.Container, rm bool)
 	var rmErrors []string
 	ctx := context.TODO()
 	for _, m := range container.MountPoints {
-		if m.Type != mounttypes.TypeVolume || m.Volume == nil {
-			continue
-		}
-		daemon.volumes.Release(ctx, m.Volume.Name(), container.ID)
-		if !rm {
-			continue
-		}
+		if m.Type == mounttypes.TypeVolume {
+			if m.Volume == nil {
+				continue
+			}
+			daemon.volumes.Release(ctx, m.Volume.Name(), container.ID)
+			if !rm {
+				continue
+			}
 
-		// Do not remove named mountpoints
-		// these are mountpoints specified like `docker run -v <name>:/foo`
-		if m.Spec.Source != "" {
-			continue
+			// Do not remove named mountpoints
+			// these are mountpoints specified like `docker run -v <name>:/foo`
+			if m.Spec.Source != "" {
+				continue
+			}
+
+			err := daemon.volumes.Remove(ctx, m.Volume.Name())
+			// Ignore volume in use errors because having this
+			// volume being referenced by other container is
+			// not an error, but an implementation detail.
+			// This prevents docker from logging "ERROR: Volume in use"
+			// where there is another container using the volume.
+			if err != nil && !volumesservice.IsInUse(err) {
+				rmErrors = append(rmErrors, err.Error())
+			}
 		}
 
-		err := daemon.volumes.Remove(ctx, m.Volume.Name())
-		// Ignore volume in use errors because having this
-		// volume being referenced by other container is
-		// not an error, but an implementation detail.
-		// This prevents docker from logging "ERROR: Volume in use"
-		// where there is another container using the volume.
-		if err != nil && !volumesservice.IsInUse(err) {
-			rmErrors = append(rmErrors, err.Error())
+		if m.Type == mounttypes.TypeImage {
+			layerName := fmt.Sprintf("%s-%s", container.ID, m.Spec.Source)
+			layer, err := daemon.imageService.GetLayerByID(layerName)
+			if err != nil {
+				rmErrors = append(rmErrors, err.Error())
+			}
+			err = daemon.imageService.ReleaseLayer(layer)
+			if err != nil {
+				rmErrors = append(rmErrors, err.Error())
+			}
+			err = layer.Unmount()
+			if err != nil {
+				rmErrors = append(rmErrors, err.Error())
+			}
 		}
 	}
 

diff --git a/daemon/volumes.go b/daemon/volumes.go
@@ -2,19 +2,22 @@ package daemon // import "github.com/docker/docker/daemon"
 
 import (
 	"context"
+	"fmt"
 	"os"
 	"path/filepath"
 	"sort"
 	"strings"
 	"time"
 
 	"github.com/containerd/log"
+	"github.com/docker/docker/api/types/backend"
 	containertypes "github.com/docker/docker/api/types/container"
 	"github.com/docker/docker/api/types/mount"
 	mounttypes "github.com/docker/docker/api/types/mount"
 	volumetypes "github.com/docker/docker/api/types/volume"
 	"github.com/docker/docker/container"
 	"github.com/docker/docker/errdefs"
+	"github.com/docker/docker/layer"
 	"github.com/docker/docker/volume"
 	volumemounts "github.com/docker/docker/volume/mounts"
 	"github.com/docker/docker/volume/service"
@@ -245,6 +248,29 @@ func (daemon *Daemon) registerMountPoints(container *container.Container, hostCo
 			}
 		}
 
+		if mp.Type == mounttypes.TypeImage {
+			img, err := daemon.imageService.GetImage(ctx, mp.Source, backend.GetImageOpts{})
+			if err != nil {
+				return err
+			}
+
+			rwLayerOpts := &layer.CreateRWLayerOpts{
+				StorageOpt: container.HostConfig.StorageOpt,
+			}
+
+			layerName := fmt.Sprintf("%s-%s", container.ID, mp.Source)
+			layer, err := daemon.imageService.CreateLayerFromImage(img, layerName, rwLayerOpts)
+			if err != nil {
+				return err
+			}
+			path, err := layer.Mount("")
+			if err != nil {
+				return err
+			}
+
+			mp.Source = path
+		}
+
 		binds[mp.Destination] = true
 		dereferenceIfExists(mp.Destination)
 		mountPoints[mp.Destination] = mp

diff --git a/volume/mounts/linux_parser.go b/volume/mounts/linux_parser.go
@@ -119,6 +119,13 @@ func (p *linuxParser) validateMountConfigImpl(mnt *mount.Mount, validateBindSour
 		if _, err := p.ConvertTmpfsOptions(mnt.TmpfsOptions, mnt.ReadOnly); err != nil {
 			return &errMountConfig{mnt, err}
 		}
+	case mount.TypeImage:
+		if mnt.BindOptions != nil {
+			return &errMountConfig{mnt, errExtraField("BindOptions")}
+		}
+		if len(mnt.Source) == 0 {
+			return &errMountConfig{mnt, errMissingField("Source")}
+		}
 	default:
 		return &errMountConfig{mnt, errors.New("mount type unknown")}
 	}
@@ -353,6 +360,15 @@ func (p *linuxParser) parseMountSpec(cfg mount.Mount, validateBindSourceExists b
 		}
 	case mount.TypeTmpfs:
 		// NOP
+	case mount.TypeImage:
+		mp.Source = cfg.Source
+		if cfg.BindOptions != nil && len(cfg.BindOptions.Propagation) > 0 {
+			mp.Propagation = cfg.BindOptions.Propagation
+		} else {
+			// If user did not specify a propagation mode, get
+			// default propagation mode.
+			mp.Propagation = linuxDefaultPropagationMode
+		}
 	}
 	return mp, nil
 }

diff --git a/volume/mounts/parser_test.go b/volume/mounts/parser_test.go
@@ -76,6 +76,10 @@ func TestParseMountSpec(t *testing.T) {
 			input:    mount.Mount{Type: mount.TypeVolume, Target: testDestinationPath + string(os.PathSeparator)},
 			expected: MountPoint{Type: mount.TypeVolume, Destination: testDestinationPath, RW: true, CopyData: parser.DefaultCopyMode()},
 		},
+		{
+			input:    mount.Mount{Type: mount.TypeImage, Source: "alpine", Target: testDestinationPath},
+			expected: MountPoint{Type: mount.TypeImage, Source: "alpine", Destination: testDestinationPath, RW: true, Propagation: parser.DefaultPropagationMode()},
+		},
 	}
 
 	for _, tc := range cases {