Overlay size option: --overlay2=all:memory,size=1g

runsc/boot/gofer_conf.go

@@ -124,19 +124,24 @@ func (l *GoferMountConfLowerType) Set(v string) error {
 
 // GoferMountConf describes how a gofer mount is configured in the sandbox.
 type GoferMountConf struct {
-	Upper GoferMountConfUpperType `json:"upper"`
 	Lower GoferMountConfLowerType `json:"lower"`
+	Upper GoferMountConfUpperType `json:"upper"`
+	Size  string                  `json:"size,omitempty"`
 }
 
 // String returns a human-readable string representing the gofer mount config.
 func (g GoferMountConf) String() string {
-	return fmt.Sprintf("%s:%s", g.Lower, g.Upper)
+	res := fmt.Sprintf("%s:%s", g.Lower, g.Upper)
+	if g.Size != "" {
+		res += ":size=" + g.Size
+	}
+	return res
 }
 
 // Set sets the value. Set(String()) should be idempotent.
 func (g *GoferMountConf) Set(v string) error {
 	parts := strings.Split(v, ":")
-	if len(parts) != 2 {
+	if len(parts) < 2 || len(parts) > 3 {
 		return fmt.Errorf("invalid gofer mount config format: %q", v)
 	}
 	if err := g.Lower.Set(parts[0]); err != nil {
@@ -145,8 +150,17 @@ func (g *GoferMountConf) Set(v string) error {
 	if err := g.Upper.Set(parts[1]); err != nil {
 		return err
 	}
+	g.Size = ""
+	if len(parts) >= 3 {
+		sizeArg := parts[2]
+		size, cut := strings.CutPrefix(sizeArg, "size=")
+		if !cut {
+			return fmt.Errorf("invalid gofer mount config format: %q", v)
+		}
+		g.Size = size
+	}
 	if !g.valid() {
-		return fmt.Errorf("invalid gofer mount config: %+v", g)
+		return fmt.Errorf("invalid gofer mount config: %q", v)
 	}
 	return nil
 }

runsc/boot/gofer_conf_test.go

@@ -175,3 +175,28 @@ func TestGoferConfFlags(t *testing.T) {
 		}
 	}
 }
+
+func TestGoferMountConfSetGet(t *testing.T) {
+	t.Run("Without size", func(t *testing.T) {
+		conf := GoferMountConf{}
+		err := conf.Set("lisafs:anon")
+		if err != nil {
+			t.Fatalf("Expect success: %v", err)
+		}
+		s := conf.String()
+		if s != "lisafs:anon" {
+			t.Fatalf("Expected lisafs:anon, got %s", s)
+		}
+	})
+	t.Run("With size", func(t *testing.T) {
+		conf := GoferMountConf{}
+		err := conf.Set("lisafs:anon:size=1719")
+		if err != nil {
+			t.Fatalf("Expect success: %v", err)
+		}
+		s := conf.String()
+		if s != "lisafs:anon:size=1719" {
+			t.Fatalf("Expected lisafs:anon:size=1719, got %s", s)
+		}
+	})
+}

runsc/boot/mount_hints.go

@@ -232,6 +232,9 @@ func (p *PodMountHints) FindMount(mountSrc string) *MountHint {
 type RootfsHint struct {
 	Mount   specs.Mount
 	Overlay config.OverlayMedium
+	// Size of overlay tmpfs. Passed as `size={Size}` to tmpfs mount.
+	// Use default if unspecified.
+	Size string
 }
 
 func (r *RootfsHint) setSource(val string) error {
@@ -252,6 +255,15 @@ func (r *RootfsHint) setType(val string) error {
 	return nil
 }
 
+func (r *RootfsHint) setOptions(val string) error {
+	size, cut := strings.CutPrefix(val, "size=")
+	if !cut {
+		return fmt.Errorf("only size= option is supported: %q", val)
+	}
+	r.Size = size
+	return nil
+}
+
 func (r *RootfsHint) setField(key, val string) error {
 	switch key {
 	case "source":
@@ -260,6 +272,8 @@ func (r *RootfsHint) setField(key, val string) error {
 		return r.setType(val)
 	case "overlay":
 		return r.Overlay.Set(val)
+	case "options":
+		return r.setOptions(val)
 	default:
 		return fmt.Errorf("invalid rootfs annotation: %s=%s", key, val)
 	}

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 mountConf.Size != "" {
+		if upperOpts.GetFilesystemOptions.Data != "" {
+			upperOpts.GetFilesystemOptions.Data += ","
+		}
+		upperOpts.GetFilesystemOptions.Data += "size=" + mountConf.Size
+	}
 
 	overlayOpts := *lowerOpts
 	overlayOpts.GetFilesystemOptions = vfs.GetFilesystemOptions{InternalMount: true}

runsc/config/config.go

@@ -906,24 +906,42 @@ 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 overlay2SizeEq = "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, ":")
+	parts := strings.Split(v, ",")
+	if len(parts) < 1 {
+		return setOverlay2Err(v)
+	}
+
+	vs := strings.Split(parts[0], ":")
 	if len(vs) != 2 {
-		return fmt.Errorf("expected format is --overlay2={mount}:{medium}, got %q", v)
+		return setOverlay2Err(v)
 	}
 
 	switch mount := vs[0]; mount {
@@ -936,7 +954,25 @@ 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(parts) == 1 {
+		o.size = ""
+	} else if len(parts) == 2 {
+		sizeArg := parts[1]
+		size, cut := strings.CutPrefix(sizeArg, overlay2SizeEq)
+		if !cut {
+			return setOverlay2Err(v)
+		}
+		o.size = size
+	} else {
+		return setOverlay2Err(v)
+	}
+
+	return nil
 }
 
 // Get implements flag.Value.
@@ -958,7 +994,13 @@ 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", overlay2SizeEq, o.size)
+	}
+
+	return res + ":" + o.medium.String() + sizeSuffix
 }
 
 // Enabled returns true if the overlay option is enabled for any mounts.
@@ -974,6 +1016,13 @@ func (o *Overlay2) RootOverlayMedium() OverlayMedium {
 	return o.medium
 }
 
+func (o *Overlay2) RootOverlaySize() string {
+	if !o.rootMount {
+		return ""
+	}
+	return o.size
+}
+
 // SubMountOverlayMedium returns the overlay medium config of submounts.
 func (o *Overlay2) SubMountOverlayMedium() OverlayMedium {
 	if !o.subMounts {
@@ -982,6 +1031,13 @@ func (o *Overlay2) SubMountOverlayMedium() OverlayMedium {
 	return o.medium
 }
 
+func (o *Overlay2) SubMountOverlaySize() string {
+	if !o.subMounts {
+		return ""
+	}
+	return o.size
+}
+
 // Medium returns the overlay medium config.
 func (o Overlay2) Medium() OverlayMedium {
 	return o.medium

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)
@@ -781,3 +786,32 @@ root = "%s"
 	}
 
 }
+
+func TestParseSerializeOverlay2(t *testing.T) {
+	t.Run("Without size", func(t *testing.T) {
+		o := Overlay2{}
+		err := o.Set("all:memory")
+		if err != nil {
+			t.Fatalf("Set failed: %v", err)
+		}
+		if o.RootOverlaySize() != "" || o.RootOverlayMedium() != "" {
+			t.Fatalf("Size mismatch, expecting empty, got %q, %q", o.RootOverlaySize(), o.SubMountOverlaySize())
+		}
+		if o.String() != "all:memory" {
+			t.Fatalf("String mismatch, expecting all:memory, got %q", o.String())
+		}
+	})
+	t.Run("With size", func(t *testing.T) {
+		o := Overlay2{}
+		err := o.Set("root:memory,size=1g")
+		if err != nil {
+			t.Fatalf("Set failed: %v", err)
+		}
+		if o.RootOverlaySize() != "1g" || o.SubMountOverlaySize() != "" {
+			t.Fatalf("Size mismatch, expecting 1g, empty, got %q, %q", o.RootOverlaySize(), o.SubMountOverlaySize())
+		}
+		if o.String() != "all:memory,size=1g" {
+			t.Fatalf("String mismatch, expecting all:memory, got %q", o.String())
+		}
+	})
+}

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")

runsc/container/container.go

@@ -899,7 +899,7 @@ func (c *Container) forEachSelfMount(fn func(mountSrc string)) {
 	}
 }
 
-func createGoferConf(overlayMedium config.OverlayMedium, mountType string, mountSrc string) (boot.GoferMountConf, error) {
+func createGoferConf(overlayMedium config.OverlayMedium, overlaySize string, mountType string, mountSrc string) (boot.GoferMountConf, error) {
 	var lower boot.GoferMountConfLowerType
 	switch mountType {
 	case boot.Bind:
@@ -915,20 +915,20 @@ func createGoferConf(overlayMedium config.OverlayMedium, mountType string, mount
 	case config.NoOverlay:
 		return boot.GoferMountConf{Lower: lower, Upper: boot.NoOverlay}, nil
 	case config.MemoryOverlay:
-		return boot.GoferMountConf{Lower: lower, Upper: boot.MemoryOverlay}, nil
+		return boot.GoferMountConf{Lower: lower, Upper: boot.MemoryOverlay, Size: overlaySize}, nil
 	case config.SelfOverlay:
 		mountSrcInfo, err := os.Stat(mountSrc)
 		if err != nil {
 			return boot.GoferMountConf{}, fmt.Errorf("failed to stat mount %q to see if it were a directory: %v", mountSrc, err)
 		}
 		if !mountSrcInfo.IsDir() {
 			log.Warningf("self filestore is only supported for directory mounts, but mount %q is not a directory, falling back to memory", mountSrc)
-			return boot.GoferMountConf{Lower: lower, Upper: boot.MemoryOverlay}, nil
+			return boot.GoferMountConf{Lower: lower, Upper: boot.MemoryOverlay, Size: overlaySize}, nil
 		}
-		return boot.GoferMountConf{Lower: lower, Upper: boot.SelfOverlay}, nil
+		return boot.GoferMountConf{Lower: lower, Upper: boot.SelfOverlay, Size: overlaySize}, nil
 	default:
 		if overlayMedium.IsBackedByAnon() {
-			return boot.GoferMountConf{Lower: lower, Upper: boot.AnonOverlay}, nil
+			return boot.GoferMountConf{Lower: lower, Upper: boot.AnonOverlay, Size: overlaySize}, nil
 		}
 		return boot.GoferMountConf{}, fmt.Errorf("unexpected overlay medium %q", overlayMedium)
 	}
@@ -939,17 +939,19 @@ func createGoferConf(overlayMedium config.OverlayMedium, mountType string, mount
 func (c *Container) initGoferConfs(ovlConf config.Overlay2, mountHints *boot.PodMountHints, rootfsHint *boot.RootfsHint) error {
 	// Handle root mount first.
 	overlayMedium := ovlConf.RootOverlayMedium()
+	overlaySize := ovlConf.RootOverlaySize()
 	mountType := boot.Bind
 	if rootfsHint != nil {
 		overlayMedium = rootfsHint.Overlay
 		if !specutils.IsGoferMount(rootfsHint.Mount) {
 			mountType = rootfsHint.Mount.Type
 		}
+		overlaySize = rootfsHint.Size
 	}
 	if c.Spec.Root.Readonly {
 		overlayMedium = config.NoOverlay
 	}
-	goferConf, err := createGoferConf(overlayMedium, mountType, c.Spec.Root.Path)
+	goferConf, err := createGoferConf(overlayMedium, overlaySize, mountType, c.Spec.Root.Path)
 	if err != nil {
 		return err
 	}
@@ -960,7 +962,8 @@ func (c *Container) initGoferConfs(ovlConf config.Overlay2, mountHints *boot.Pod
 		if !specutils.IsGoferMount(c.Spec.Mounts[i]) {
 			continue
 		}
-		overlayMedium = ovlConf.SubMountOverlayMedium()
+		overlayMedium := ovlConf.SubMountOverlayMedium()
+		overlaySize := ovlConf.SubMountOverlaySize()
 		mountType = boot.Bind
 		if specutils.IsReadonlyMount(c.Spec.Mounts[i].Options) {
 			overlayMedium = config.NoOverlay
@@ -972,8 +975,9 @@ func (c *Container) initGoferConfs(ovlConf config.Overlay2, mountHints *boot.Pod
 			if !specutils.IsGoferMount(hint.Mount) {
 				mountType = hint.Mount.Type
 			}
+			overlaySize = ""
 		}
-		goferConf, err := createGoferConf(overlayMedium, mountType, c.Spec.Mounts[i].Source)
+		goferConf, err := createGoferConf(overlayMedium, overlaySize, mountType, c.Spec.Mounts[i].Source)
 		if err != nil {
 			return err
 		}