cache: Disable overlay diff for native snapshotter

Before this change, test cases were running with an env var that forces
the overlay differ to be on even when the native snapshotter was being
used, which resulted in failures. Now, that env var is skipped when
using the native snapshotter.

Additionally, this includes a related change to skip even trying to use
the overlay differ when the native snapshotter is in use. Previously,
the blob creation code first tried to use the overlay differ and then
failed and fell back to the double-walking differ. Now, it just jumps
right to the double-walking differ when the native snapshotter is in
use.

Signed-off-by: Erik Sipsma <erik@sipsma.dev>

cache/blobs.go

@@ -137,7 +137,7 @@ func computeBlobChain(ctx context.Context, sr *immutableRef, createIfNeeded bool
 					case "overlayfs", "stargz":
 						// overlayfs-based snapshotters should support overlay diff. so print warn log on failure.
 						logWarnOnErr = true
-					case "fuse-overlayfs":
+					case "fuse-overlayfs", "native":
 						// not supported with fuse-overlayfs snapshotter which doesn't provide overlayfs mounts.
 						// TODO: add support for fuse-overlayfs
 						enableOverlay = false

util/testutil/integration/containerd.go

@@ -9,6 +9,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"runtime"
 	"strings"
 	"time"
 
@@ -148,6 +149,9 @@ disabled_plugins = ["cri"]
 		"--containerd-worker-labels=org.mobyproject.buildkit.worker.sandbox=true", // Include use of --containerd-worker-labels to trigger https://github.com/moby/buildkit/pull/603
 	}, snBuildkitdArgs...)
 
+	if runtime.GOOS != "windows" && c.snapshotter != "native" {
+		c.extraEnv = append(c.extraEnv, "BUILDKIT_DEBUG_FORCE_OVERLAY_DIFF=true")
+	}
 	buildkitdSock, stop, err := runBuildkitd(ctx, cfg, buildkitdArgs, cfg.Logs, 0, 0, c.extraEnv)
 	if err != nil {
 		printLogs(cfg.Logs, log.Println)

util/testutil/integration/oci.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"runtime"
 
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
@@ -68,7 +69,11 @@ func (s *oci) New(ctx context.Context, cfg *BackendConfig) (Backend, func() erro
 		buildkitdArgs = append([]string{"sudo", "-u", fmt.Sprintf("#%d", s.uid), "-i", "--", "exec", "rootlesskit"}, buildkitdArgs...)
 	}
 
-	buildkitdSock, stop, err := runBuildkitd(ctx, cfg, buildkitdArgs, cfg.Logs, s.uid, s.gid, nil)
+	var extraEnv []string
+	if runtime.GOOS != "windows" && s.snapshotter != "native" {
+		extraEnv = append(extraEnv, "BUILDKIT_DEBUG_FORCE_OVERLAY_DIFF=true")
+	}
+	buildkitdSock, stop, err := runBuildkitd(ctx, cfg, buildkitdArgs, cfg.Logs, s.uid, s.gid, extraEnv)
 	if err != nil {
 		printLogs(cfg.Logs, log.Println)
 		return nil, nil, err

util/testutil/integration/sandbox.go

@@ -182,9 +182,6 @@ func runBuildkitd(ctx context.Context, conf *BackendConfig, args []string, logs
 	args = append(args, "--root", tmpdir, "--addr", address, "--debug")
 	cmd := exec.Command(args[0], args[1:]...)
 	cmd.Env = append(os.Environ(), "BUILDKIT_DEBUG_EXEC_OUTPUT=1", "BUILDKIT_DEBUG_PANIC_ON_ERROR=1", "TMPDIR="+filepath.Join(tmpdir, "tmp"))
-	if runtime.GOOS != "windows" {
-		cmd.Env = append(cmd.Env, "BUILDKIT_DEBUG_FORCE_OVERLAY_DIFF=true")
-	}
 	cmd.Env = append(cmd.Env, extraEnv...)
 	cmd.SysProcAttr = getSysProcAttr()