Option --overlay-size

Author: stepancheg

runsc/boot/vfs.go

@@ -585,6 +585,12 @@ func (c *containerMounter) configureOverlay(ctx context.Context, conf *config.Co
 	// filesystem specific options.
 	upperOpts := *lowerOpts
 	upperOpts.GetFilesystemOptions = vfs.GetFilesystemOptions{InternalMount: true}
+	if conf.GetOverlay2().Size() != "" {
+		if upperOpts.GetFilesystemOptions.Data != "" {
+			upperOpts.GetFilesystemOptions.Data += ","
+		}
+		upperOpts.GetFilesystemOptions.Data += "size=" + conf.GetOverlay2().Size()
+	}
 
 	overlayOpts := *lowerOpts
 	overlayOpts.GetFilesystemOptions = vfs.GetFilesystemOptions{InternalMount: true}

runsc/config/config.go

@@ -906,24 +906,37 @@ type Overlay2 struct {
 	rootMount bool
 	subMounts bool
 	medium    OverlayMedium
+	// Size of overlay upper layer.
+	// Passed as is to tmpfs mount, as `size={size}`.
+	// Empty means use default.
+	// Size is applied to each overlay independently and not shared by overlays.
+	size string
 }
 
 func defaultOverlay2() *Overlay2 {
 	// Rootfs overlay is enabled by default and backed by a file in rootfs itself.
 	return &Overlay2{rootMount: true, subMounts: false, medium: SelfOverlay}
 }
 
+func setOverlay2Err(v string) error {
+	return fmt.Errorf("expected format is --overlay2={mount}:{medium}[:size={size}], got %q", v)
+}
+
+// `--overlay2=...` param `size=`.
+const overlaySizeEq = "size="
+
 // Set implements flag.Value. Set(String()) should be idempotent.
 func (o *Overlay2) Set(v string) error {
 	if v == "none" {
 		o.rootMount = false
 		o.subMounts = false
 		o.medium = NoOverlay
+		o.size = ""
 		return nil
 	}
 	vs := strings.Split(v, ":")
-	if len(vs) != 2 {
-		return fmt.Errorf("expected format is --overlay2={mount}:{medium}, got %q", v)
+	if len(vs) < 2 {
+		return setOverlay2Err(v)
 	}
 
 	switch mount := vs[0]; mount {
@@ -936,7 +949,24 @@ func (o *Overlay2) Set(v string) error {
 		return fmt.Errorf("unexpected mount specifier for --overlay2: %q", mount)
 	}
 
-	return o.medium.Set(vs[1])
+	err := o.medium.Set(vs[1])
+	if err != nil {
+		return err
+	}
+
+	if len(vs) == 2 {
+		o.size = ""
+	} else if len(vs) == 3 {
+		sizeArg := vs[2]
+		if !strings.HasPrefix(sizeArg, overlaySizeEq) {
+			return setOverlay2Err(v)
+		}
+		o.size = strings.TrimPrefix(sizeArg, overlaySizeEq)
+	} else {
+		return setOverlay2Err(v)
+	}
+
+	return nil
 }
 
 // Get implements flag.Value.
@@ -958,7 +988,13 @@ func (o Overlay2) String() string {
 	default:
 		panic("invalid state of subMounts = true and rootMount = false")
 	}
-	return res + ":" + o.medium.String()
+
+	var sizeSuffix string
+	if o.size != "" {
+		sizeSuffix = fmt.Sprintf(":%s%s", overlaySizeEq, o.size)
+	}
+
+	return res + ":" + o.medium.String() + sizeSuffix
 }
 
 // Enabled returns true if the overlay option is enabled for any mounts.
@@ -987,6 +1023,11 @@ func (o Overlay2) Medium() OverlayMedium {
 	return o.medium
 }
 
+// Size returns the overlay upper layer size, or empty string if default should be used.
+func (o Overlay2) Size() string {
+	return o.size
+}
+
 // HostSettingsPolicy dictates how host settings should be handled.
 type HostSettingsPolicy int
 

runsc/config/config_test.go

@@ -231,6 +231,11 @@ func TestInvalidFlags(t *testing.T) {
 			value: "root:dir=tmp",
 			error: "overlay host file directory should be an absolute path, got \"tmp\"",
 		},
+		{
+			name:  "overlay2",
+			value: "root:memory:sz=sdg",
+			error: "expected format is --overlay2",
+		},
 	} {
 		t.Run(tc.name, func(t *testing.T) {
 			testFlags := flag.NewFlagSet("test", flag.ContinueOnError)
@@ -778,3 +783,26 @@ root = "%s"
 	}
 
 }
+
+func TestParseOverlay2(t *testing.T) {
+	t.Run("Parse without size", func(t *testing.T) {
+		o := Overlay2{}
+		err := o.Set("all:memory")
+		if err != nil {
+			t.Fatalf("Set failed: %v", err)
+		}
+		if o.Size() != "" {
+			t.Fatalf("Size mismatch, expecting empty string, got %q", o.Size())
+		}
+	})
+	t.Run("Parse with size", func(t *testing.T) {
+		o := Overlay2{}
+		err := o.Set("all:memory:size=1g")
+		if err != nil {
+			t.Fatalf("Set failed: %v", err)
+		}
+		if o.Size() != "1g" {
+			t.Fatalf("Size mismatch, expecting 1g, got %q", o.Size())
+		}
+	})
+}

runsc/config/flags.go

@@ -116,7 +116,12 @@ func RegisterFlags(flagSet *flag.FlagSet) {
 	flagSet.Var(fileAccessTypePtr(FileAccessExclusive), "file-access", "specifies which filesystem validation to use for the root mount: exclusive (default), shared.")
 	flagSet.Var(fileAccessTypePtr(FileAccessShared), "file-access-mounts", "specifies which filesystem validation to use for volumes other than the root mount: shared (default), exclusive.")
 	flagSet.Bool("overlay", false, "DEPRECATED: use --overlay2=all:memory to achieve the same effect")
-	flagSet.Var(defaultOverlay2(), flagOverlay2, "wrap mounts with overlayfs. Format is {mount}:{medium}, where 'mount' can be 'root' or 'all' and medium can be 'memory', 'self' or 'dir=/abs/dir/path' in which filestore will be created. 'none' will turn overlay mode off.")
+	flagSet.Var(defaultOverlay2(), flagOverlay2, "wrap mounts with overlayfs. Format is\n"+
+		"* 'none' to turn overlay mode off\n"+
+		"* {mount}:{medium}[size={size}], where\n"+
+		"    'mount' can be 'root' or 'all'\n"+
+		"    'medium' can be 'memory', 'self' or 'dir=/abs/dir/path' in which filestore will be created\n"+
+		"    'size' optional parameter overrides default overlay upper layer size\n")
 	flagSet.Bool("fsgofer-host-uds", false, "DEPRECATED: use host-uds=all")
 	flagSet.Var(hostUDSPtr(HostUDSNone), flagHostUDS, "controls permission to access host Unix-domain sockets. Values: none|open|create|all, default: none")
 	flagSet.Var(hostFifoPtr(HostFifoNone), "host-fifo", "controls permission to access host FIFOs (or named pipes). Values: none|open, default: none")