Enable VFS2 by default

This change enables VFS2 by default. VFS2 is much faster than the previous
implementation and it's also more compatible. VFS1 is no longer supported and
will be deleted from the code.

Use `--vfs2=false` if you need to disable it. Make sure to report a bug if you
have the need to disable VFS2 or something is not working for you.

Closes #1035

PiperOrigin-RevId: 404898135

runsc/config/flags.go

@@ -80,7 +80,7 @@ func RegisterFlags() {
 		flag.Bool("overlay", false, "wrap filesystem mounts with writable overlay. All modifications are stored in memory inside the sandbox.")
 		flag.Bool("verity", false, "specifies whether a verity file system will be mounted.")
 		flag.Bool("fsgofer-host-uds", false, "allow the gofer to mount Unix Domain Sockets.")
-		flag.Bool("vfs2", false, "enables VFSv2. This uses the new VFS layer that is faster than the previous one.")
+		flag.Bool("vfs2", true, "enables VFSv2. This uses the new VFS layer that is faster than the previous one.")
 		flag.Bool("fuse", false, "TEST ONLY; use while FUSE in VFSv2 is landing. This allows the use of the new experimental FUSE filesystem.")
 		flag.Bool("lisafs", false, "Enables lisafs protocol instead of 9P. This is only effective with VFS2.")
 		flag.Bool("cgroupfs", false, "Automatically mount cgroupfs.")

runsc/container/container_test.go

@@ -407,9 +407,9 @@ var (
 func configsHelper(t *testing.T, opts ...configOption) map[string]*config.Config {
 	// Always load the default config.
 	cs := make(map[string]*config.Config)
-	testutil.TestConfig(t)
 	for _, o := range opts {
 		c := testutil.TestConfig(t)
+		c.VFS2 = false
 		switch o {
 		case overlay:
 			c.Overlay = true
@@ -2615,6 +2615,8 @@ func TestCat(t *testing.T) {
 	f.Close()
 
 	spec, conf := sleepSpecConf(t)
+	// TODO(gvisor.dev/issue/6742): Add VFS2 support.
+	conf.VFS2 = false
 
 	_, bundleDir, cleanup, err := testutil.SetupContainer(spec, conf)
 	if err != nil {

test/runner/main.go

@@ -180,11 +180,9 @@ func runRunsc(tc gtest.TestCase, spec *specs.Spec) error {
 	if *overlay {
 		args = append(args, "-overlay")
 	}
-	if *vfs2 {
-		args = append(args, "-vfs2")
-		if *fuse {
-			args = append(args, "-fuse")
-		}
+	args = append(args, fmt.Sprintf("-vfs2=%t", *vfs2))
+	if *vfs2 && *fuse {
+		args = append(args, "-fuse")
 	}
 	if *debug {
 		args = append(args, "-debug", "-log-packets=true")