mount: Add From/ToProto helpers

Helpers to convert from containerd's [Mount] to its protobuf structure for
[Mount] and vice-versa appear three times. It seems sane to just expose
this facility in /mount.

Signed-off-by: Danny Canter <danny@dcantah.dev>

contrib/diffservice/service.go

@@ -50,7 +50,7 @@ func (s *service) Apply(ctx context.Context, er *diffapi.ApplyRequest) (*diffapi
 		ocidesc ocispec.Descriptor
 		err     error
 		desc    = toDescriptor(er.Diff)
-		mounts  = toMounts(er.Mounts)
+		mounts  = mount.FromProto(er.Mounts)
 	)
 
 	var opts []diff.ApplyOpt
@@ -79,8 +79,8 @@ func (s *service) Diff(ctx context.Context, dr *diffapi.DiffRequest) (*diffapi.D
 	var (
 		ocidesc ocispec.Descriptor
 		err     error
-		aMounts = toMounts(dr.Left)
+		aMounts = mount.FromProto(dr.Left)
-		bMounts = toMounts(dr.Right)
+		bMounts = mount.FromProto(dr.Right)
 	)
 
 	var opts []diff.Opt
@@ -108,19 +108,6 @@ func (s *service) Diff(ctx context.Context, dr *diffapi.DiffRequest) (*diffapi.D
 	}, nil
 }
 
-func toMounts(apim []*types.Mount) []mount.Mount {
-	mounts := make([]mount.Mount, len(apim))
-	for i, m := range apim {
-		mounts[i] = mount.Mount{
-			Type:    m.Type,
-			Source:  m.Source,
-			Target:  m.Target,
-			Options: m.Options,
-		}
-	}
-	return mounts
-}
-
 func toDescriptor(d *types.Descriptor) ocispec.Descriptor {
 	return ocispec.Descriptor{
 		MediaType:   d.MediaType,

contrib/snapshotservice/service.go

@@ -20,7 +20,6 @@ import (
 	"context"
 
 	snapshotsapi "github.com/containerd/containerd/api/services/snapshots/v1"
-	"github.com/containerd/containerd/api/types"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/mount"
 	"github.com/containerd/containerd/protobuf"
@@ -51,7 +50,7 @@ func (s service) Prepare(ctx context.Context, pr *snapshotsapi.PrepareSnapshotRe
 	}
 
 	return &snapshotsapi.PrepareSnapshotResponse{
-		Mounts: fromMounts(mounts),
+		Mounts: mount.ToProto(mounts),
 	}, nil
 }
 
@@ -65,7 +64,7 @@ func (s service) View(ctx context.Context, pr *snapshotsapi.ViewSnapshotRequest)
 		return nil, errdefs.ToGRPC(err)
 	}
 	return &snapshotsapi.ViewSnapshotResponse{
-		Mounts: fromMounts(mounts),
+		Mounts: mount.ToProto(mounts),
 	}, nil
 }
 
@@ -75,7 +74,7 @@ func (s service) Mounts(ctx context.Context, mr *snapshotsapi.MountsRequest) (*s
 		return nil, errdefs.ToGRPC(err)
 	}
 	return &snapshotsapi.MountsResponse{
-		Mounts: fromMounts(mounts),
+		Mounts: mount.ToProto(mounts),
 	}, nil
 }
 
@@ -199,19 +198,6 @@ func fromInfo(info snapshots.Info) *snapshotsapi.Info {
 	}
 }
 
-func fromMounts(mounts []mount.Mount) []*types.Mount {
-	out := make([]*types.Mount, len(mounts))
-	for i, m := range mounts {
-		out[i] = &types.Mount{
-			Type:    m.Type,
-			Source:  m.Source,
-			Target:  m.Target,
-			Options: m.Options,
-		}
-	}
-	return out
-}
-
 func toInfo(info *snapshotsapi.Info) snapshots.Info {
 	return snapshots.Info{
 		Name:    info.Name,

diff/proxy/differ.go

@@ -60,7 +60,7 @@ func (r *diffRemote) Apply(ctx context.Context, desc ocispec.Descriptor, mounts
 
 	req := &diffapi.ApplyRequest{
 		Diff:     fromDescriptor(desc),
-		Mounts:   fromMounts(mounts),
+		Mounts:   mount.ToProto(mounts),
 		Payloads: payloads,
 	}
 	resp, err := r.client.Apply(ctx, req)
@@ -85,8 +85,8 @@ func (r *diffRemote) Compare(ctx context.Context, a, b []mount.Mount, opts ...di
 		sourceDateEpoch = timestamppb.New(*config.SourceDateEpoch)
 	}
 	req := &diffapi.DiffRequest{
-		Left:            fromMounts(a),
+		Left:            mount.ToProto(a),
-		Right:           fromMounts(b),
+		Right:           mount.ToProto(b),
 		MediaType:       config.MediaType,
 		Ref:             config.Reference,
 		Labels:          config.Labels,
@@ -119,16 +119,3 @@ func fromDescriptor(d ocispec.Descriptor) *types.Descriptor {
 		Annotations: d.Annotations,
 	}
 }
-
-func fromMounts(mounts []mount.Mount) []*types.Mount {
-	apiMounts := make([]*types.Mount, len(mounts))
-	for i, m := range mounts {
-		apiMounts[i] = &types.Mount{
-			Type:    m.Type,
-			Source:  m.Source,
-			Target:  m.Target,
-			Options: m.Options,
-		}
-	}
-	return apiMounts
-}

mount/mount.go

@@ -20,6 +20,7 @@ import (
 	"fmt"
 	"strings"
 
+	"github.com/containerd/containerd/api/types"
 	"github.com/containerd/continuity/fs"
 )
 
@@ -130,3 +131,33 @@ func readonlyOverlay(opt []string) []string {
 	}
 	return out
 }
+
+// ToProto converts from [Mount] to the containerd
+// APIs protobuf definition of a Mount.
+func ToProto(mounts []Mount) []*types.Mount {
+	apiMounts := make([]*types.Mount, len(mounts))
+	for i, m := range mounts {
+		apiMounts[i] = &types.Mount{
+			Type:    m.Type,
+			Source:  m.Source,
+			Target:  m.Target,
+			Options: m.Options,
+		}
+	}
+	return apiMounts
+}
+
+// FromProto converts from the protobuf definition [types.Mount] to
+// [Mount].
+func FromProto(mm []*types.Mount) []Mount {
+	mounts := make([]Mount, len(mm))
+	for i, m := range mm {
+		mounts[i] = Mount{
+			Type:    m.Type,
+			Source:  m.Source,
+			Target:  m.Target,
+			Options: m.Options,
+		}
+	}
+	return mounts
+}

services/diff/local.go

@@ -98,7 +98,7 @@ func (l *local) Apply(ctx context.Context, er *diffapi.ApplyRequest, _ ...grpc.C
 		ocidesc ocispec.Descriptor
 		err     error
 		desc    = toDescriptor(er.Diff)
-		mounts  = toMounts(er.Mounts)
+		mounts  = mount.FromProto(er.Mounts)
 	)
 
 	var opts []diff.ApplyOpt
@@ -131,8 +131,8 @@ func (l *local) Diff(ctx context.Context, dr *diffapi.DiffRequest, _ ...grpc.Cal
 	var (
 		ocidesc ocispec.Descriptor
 		err     error
-		aMounts = toMounts(dr.Left)
+		aMounts = mount.FromProto(dr.Left)
-		bMounts = toMounts(dr.Right)
+		bMounts = mount.FromProto(dr.Right)
 	)
 
 	var opts []diff.Opt
@@ -165,19 +165,6 @@ func (l *local) Diff(ctx context.Context, dr *diffapi.DiffRequest, _ ...grpc.Cal
 	}, nil
 }
 
-func toMounts(apim []*types.Mount) []mount.Mount {
-	mounts := make([]mount.Mount, len(apim))
-	for i, m := range apim {
-		mounts[i] = mount.Mount{
-			Type:    m.Type,
-			Source:  m.Source,
-			Target:  m.Target,
-			Options: m.Options,
-		}
-	}
-	return mounts
-}
-
 func toDescriptor(d *types.Descriptor) ocispec.Descriptor {
 	return ocispec.Descriptor{
 		MediaType:   d.MediaType,

services/snapshots/service.go

@@ -21,7 +21,6 @@ import (
 	"errors"
 
 	snapshotsapi "github.com/containerd/containerd/api/services/snapshots/v1"
-	"github.com/containerd/containerd/api/types"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/log"
 	"github.com/containerd/containerd/mount"
@@ -102,7 +101,7 @@ func (s *service) Prepare(ctx context.Context, pr *snapshotsapi.PrepareSnapshotR
 	}
 
 	return &snapshotsapi.PrepareSnapshotResponse{
-		Mounts: fromMounts(mounts),
+		Mounts: mount.ToProto(mounts),
 	}, nil
 }
 
@@ -121,7 +120,7 @@ func (s *service) View(ctx context.Context, pr *snapshotsapi.ViewSnapshotRequest
 		return nil, errdefs.ToGRPC(err)
 	}
 	return &snapshotsapi.ViewSnapshotResponse{
-		Mounts: fromMounts(mounts),
+		Mounts: mount.ToProto(mounts),
 	}, nil
 }
 
@@ -137,7 +136,7 @@ func (s *service) Mounts(ctx context.Context, mr *snapshotsapi.MountsRequest) (*
 		return nil, errdefs.ToGRPC(err)
 	}
 	return &snapshotsapi.MountsResponse{
-		Mounts: fromMounts(mounts),
+		Mounts: mount.ToProto(mounts),
 	}, nil
 }
 
@@ -304,19 +303,6 @@ func fromUsage(usage snapshots.Usage) *snapshotsapi.UsageResponse {
 	}
 }
 
-func fromMounts(mounts []mount.Mount) []*types.Mount {
-	out := make([]*types.Mount, len(mounts))
-	for i, m := range mounts {
-		out[i] = &types.Mount{
-			Type:    m.Type,
-			Source:  m.Source,
-			Target:  m.Target,
-			Options: m.Options,
-		}
-	}
-	return out
-}
-
 func toInfo(info *snapshotsapi.Info) snapshots.Info {
 	return snapshots.Info{
 		Name:    info.Name,

snapshots/proxy/proxy.go

@@ -21,7 +21,6 @@ import (
 	"io"
 
 	snapshotsapi "github.com/containerd/containerd/api/services/snapshots/v1"
-	"github.com/containerd/containerd/api/types"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/mount"
 	"github.com/containerd/containerd/protobuf"
@@ -89,7 +88,7 @@ func (p *proxySnapshotter) Mounts(ctx context.Context, key string) ([]mount.Moun
 	if err != nil {
 		return nil, errdefs.FromGRPC(err)
 	}
-	return toMounts(resp.Mounts), nil
+	return mount.FromProto(resp.Mounts), nil
 }
 
 func (p *proxySnapshotter) Prepare(ctx context.Context, key, parent string, opts ...snapshots.Opt) ([]mount.Mount, error) {
@@ -108,7 +107,7 @@ func (p *proxySnapshotter) Prepare(ctx context.Context, key, parent string, opts
 	if err != nil {
 		return nil, errdefs.FromGRPC(err)
 	}
-	return toMounts(resp.Mounts), nil
+	return mount.FromProto(resp.Mounts), nil
 }
 
 func (p *proxySnapshotter) View(ctx context.Context, key, parent string, opts ...snapshots.Opt) ([]mount.Mount, error) {
@@ -127,7 +126,7 @@ func (p *proxySnapshotter) View(ctx context.Context, key, parent string, opts ..
 	if err != nil {
 		return nil, errdefs.FromGRPC(err)
 	}
-	return toMounts(resp.Mounts), nil
+	return mount.FromProto(resp.Mounts), nil
 }
 
 func (p *proxySnapshotter) Commit(ctx context.Context, name, key string, opts ...snapshots.Opt) error {
@@ -220,19 +219,6 @@ func toUsage(resp *snapshotsapi.UsageResponse) snapshots.Usage {
 	}
 }
 
-func toMounts(mm []*types.Mount) []mount.Mount {
-	mounts := make([]mount.Mount, len(mm))
-	for i, m := range mm {
-		mounts[i] = mount.Mount{
-			Type:    m.Type,
-			Source:  m.Source,
-			Target:  m.Target,
-			Options: m.Options,
-		}
-	}
-	return mounts
-}
-
 func fromKind(kind snapshots.Kind) snapshotsapi.Kind {
 	if kind == snapshots.KindActive {
 		return snapshotsapi.Kind_ACTIVE