Move checkpoint filenames to a new package.

pkg/sentry/state/checkpointfiles/BUILD

@@ -0,0 +1,12 @@
+load("//tools:defs.bzl", "go_library")
+
+package(
+    default_applicable_licenses = ["//:license"],
+    licenses = ["notice"],
+)
+
+go_library(
+    name = "checkpointfiles",
+    srcs = ["checkpointfiles.go"],
+    visibility = ["//pkg/sentry:internal"],
+)

pkg/sentry/state/checkpointfiles/checkpointfiles.go

@@ -0,0 +1,31 @@
+// Copyright 2025 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 checkpointfiles defines constants used when sentry state is
+// checkpointed to multiple files in a directory rather than to an opaque FD.
+package checkpointfiles
+
+const (
+	// StateFileName is the file in an image-path directory which contains the
+	// sentry object graph.
+	StateFileName = "checkpoint.img"
+
+	// PagesMetadataFileName is the file in an image-path directory containing
+	// MemoryFile metadata.
+	PagesMetadataFileName = "pages_meta.img"
+
+	// PagesFileName is the file in an image-path directory containing
+	// MemoryFile page contents.
+	PagesFileName = "pages.img"
+)

runsc/boot/restore.go

@@ -50,15 +50,6 @@ import (
 )
 
 const (
-	// CheckpointStateFileName is the file within the given image-path's
-	// directory which contains the container's saved state.
-	CheckpointStateFileName = "checkpoint.img"
-	// CheckpointPagesMetadataFileName is the file within the given image-path's
-	// directory containing the container's MemoryFile metadata.
-	CheckpointPagesMetadataFileName = "pages_meta.img"
-	// CheckpointPagesFileName is the file within the given image-path's
-	// directory containing the container's MemoryFile pages.
-	CheckpointPagesFileName = "pages.img"
 	// VersionKey is the key used to save runsc version in the save metadata and compare
 	// it across checkpoint restore.
 	VersionKey = "runsc_version"

runsc/sandbox/BUILD

@@ -38,6 +38,7 @@ go_library(
         "//pkg/sentry/platform",
         "//pkg/sentry/seccheck",
         "//pkg/sentry/socket/plugin",
+        "//pkg/sentry/state/checkpointfiles",
         "//pkg/state/statefile",
         "//pkg/sync",
         "//pkg/tcpip/header",

runsc/sandbox/sandbox.go

@@ -50,6 +50,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/erofs"
 	"gvisor.dev/gvisor/pkg/sentry/platform"
 	"gvisor.dev/gvisor/pkg/sentry/seccheck"
+	"gvisor.dev/gvisor/pkg/sentry/state/checkpointfiles"
 	"gvisor.dev/gvisor/pkg/state/statefile"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/urpc"
@@ -501,7 +502,7 @@ func (s *Sandbox) Restore(conf *config.Config, spec *specs.Spec, cid string, ima
 
 	log.Debugf("Restore sandbox %q from path %q", s.ID, imagePath)
 
-	stateFileName := path.Join(imagePath, boot.CheckpointStateFileName)
+	stateFileName := path.Join(imagePath, checkpointfiles.StateFileName)
 	sf, err := os.Open(stateFileName)
 	if err != nil {
 		return fmt.Errorf("opening state file %q failed: %v", stateFileName, err)
@@ -516,15 +517,15 @@ func (s *Sandbox) Restore(conf *config.Config, spec *specs.Spec, cid string, ima
 	}
 
 	// If the pages file exists, we must pass it in.
-	pagesFileName := path.Join(imagePath, boot.CheckpointPagesFileName)
+	pagesFileName := path.Join(imagePath, checkpointfiles.PagesFileName)
 	pagesReadFlags := os.O_RDONLY
 	if direct {
 		// The contents are page-aligned, so it can be opened with O_DIRECT.
 		pagesReadFlags |= syscall.O_DIRECT
 	}
 	if pf, err := os.OpenFile(pagesFileName, pagesReadFlags, 0); err == nil {
 		defer pf.Close()
-		pagesMetadataFileName := path.Join(imagePath, boot.CheckpointPagesMetadataFileName)
+		pagesMetadataFileName := path.Join(imagePath, checkpointfiles.PagesMetadataFileName)
 		pmf, err := os.Open(pagesMetadataFileName)
 		if err != nil {
 			return fmt.Errorf("opening restore image file %q failed: %v", pagesMetadataFileName, err)
@@ -1537,7 +1538,7 @@ func (s *Sandbox) Checkpoint(cid string, imagePath string, opts CheckpointOpts)
 func createSaveFiles(path string, direct bool, compression statefile.CompressionLevel) ([]*os.File, error) {
 	var files []*os.File
 
-	stateFilePath := filepath.Join(path, boot.CheckpointStateFileName)
+	stateFilePath := filepath.Join(path, checkpointfiles.StateFileName)
 	f, err := os.OpenFile(stateFilePath, os.O_CREATE|os.O_EXCL|os.O_RDWR, 0644)
 	if err != nil {
 		return nil, fmt.Errorf("creating checkpoint state file %q: %w", stateFilePath, err)
@@ -1548,14 +1549,14 @@ func createSaveFiles(path string, direct bool, compression statefile.Compression
 	// It is beneficial to store them separately so certain optimizations can be
 	// applied during restore. See Restore().
 	if compression == statefile.CompressionLevelNone {
-		pagesMetadataFilePath := filepath.Join(path, boot.CheckpointPagesMetadataFileName)
+		pagesMetadataFilePath := filepath.Join(path, checkpointfiles.PagesMetadataFileName)
 		f, err = os.OpenFile(pagesMetadataFilePath, os.O_CREATE|os.O_EXCL|os.O_RDWR, 0644)
 		if err != nil {
 			return nil, fmt.Errorf("creating checkpoint pages metadata file %q: %w", pagesMetadataFilePath, err)
 		}
 		files = append(files, f)
 
-		pagesFilePath := filepath.Join(path, boot.CheckpointPagesFileName)
+		pagesFilePath := filepath.Join(path, checkpointfiles.PagesFileName)
 		pagesWriteFlags := os.O_CREATE | os.O_EXCL | os.O_RDWR
 		if direct {
 			// The writes will be page-aligned, so it can be opened with O_DIRECT.