1 files changed, 117 insertions, 0 deletions
diff --git a/pkg/sentry/vfs/save_restore.go b/pkg/sentry/vfs/save_restore.go
new file mode 100644
index 000000000..7aa073510
--- /dev/null
+++ b/pkg/sentry/vfs/save_restore.go
@@ -0,0 +1,117 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package vfs
+
+import (
+	"fmt"
+	"sync/atomic"
+
+	"gvisor.dev/gvisor/pkg/context"
+)
+
+// FilesystemImplSaveRestoreExtension is an optional extension to
+// FilesystemImpl.
+type FilesystemImplSaveRestoreExtension interface {
+	// PrepareSave prepares this filesystem for serialization.
+	PrepareSave(ctx context.Context) error
+
+	// CompleteRestore completes restoration from checkpoint for this
+	// filesystem after deserialization.
+	CompleteRestore(ctx context.Context, opts CompleteRestoreOptions) error
+}
+
+// PrepareSave prepares all filesystems for serialization.
+func (vfs *VirtualFilesystem) PrepareSave(ctx context.Context) error {
+	failures := 0
+	for fs := range vfs.getFilesystems() {
+		if ext, ok := fs.impl.(FilesystemImplSaveRestoreExtension); ok {
+			if err := ext.PrepareSave(ctx); err != nil {
+				ctx.Warningf("%T.PrepareSave failed: %v", fs.impl, err)
+				failures++
+			}
+		}
+		fs.DecRef(ctx)
+	}
+	if failures != 0 {
+		return fmt.Errorf("%d filesystems failed to prepare for serialization", failures)
+	}
+	return nil
+}
+
+// CompleteRestore completes restoration from checkpoint for all filesystems
+// after deserialization.
+func (vfs *VirtualFilesystem) CompleteRestore(ctx context.Context, opts *CompleteRestoreOptions) error {
+	failures := 0
+	for fs := range vfs.getFilesystems() {
+		if ext, ok := fs.impl.(FilesystemImplSaveRestoreExtension); ok {
+			if err := ext.CompleteRestore(ctx, *opts); err != nil {
+				ctx.Warningf("%T.CompleteRestore failed: %v", fs.impl, err)
+				failures++
+			}
+		}
+		fs.DecRef(ctx)
+	}
+	if failures != 0 {
+		return fmt.Errorf("%d filesystems failed to complete restore after deserialization", failures)
+	}
+	return nil
+}
+
+// CompleteRestoreOptions contains options to
+// VirtualFilesystem.CompleteRestore() and
+// FilesystemImplSaveRestoreExtension.CompleteRestore().
+type CompleteRestoreOptions struct {
+	// If ValidateFileSizes is true, filesystem implementations backed by
+	// remote filesystems should verify that file sizes have not changed
+	// between checkpoint and restore.
+	ValidateFileSizes bool
+
+	// If ValidateFileModificationTimestamps is true, filesystem
+	// implementations backed by remote filesystems should validate that file
+	// mtimes have not changed between checkpoint and restore.
+	ValidateFileModificationTimestamps bool
+}
+
+// saveMounts is called by stateify.
+func (vfs *VirtualFilesystem) saveMounts() []*Mount {
+	if atomic.LoadPointer(&vfs.mounts.slots) == nil {
+		// vfs.Init() was never called.
+		return nil
+	}
+	var mounts []*Mount
+	vfs.mounts.Range(func(mount *Mount) bool {
+		mounts = append(mounts, mount)
+		return true
+	})
+	return mounts
+}
+
+// loadMounts is called by stateify.
+func (vfs *VirtualFilesystem) loadMounts(mounts []*Mount) {
+	if mounts == nil {
+		return
+	}
+	vfs.mounts.Init()
+	for _, mount := range mounts {
+		vfs.mounts.Insert(mount)
+	}
+}
+
+// afterLoad is called by stateify.
+func (epi *epollInterest) afterLoad() {
+	// Mark all epollInterests as ready after restore so that the next call to
+	// EpollInstance.ReadEvents() rechecks their readiness.
+	epi.Callback(nil)
+}