libimage: speed up image filters

With commit 86afb94 the dangling checks have been changed to be
compatible with Docker.  Since then, the dangling also need to compute
children.

Speed up the dangling and intermediate checks by computing the layer
tree *once* instead of for each filter invocation.

**Before:**
real    0m10.837s
user    0m11.308s
sys     0m4.231s

**After:**
real    0m0.476s
user    0m0.478s
sys     0m0.151s

Context: github.com/containers/podman/issues/11997
Signed-off-by: Valentin Rothberg <[email protected]>

libimage/filters.go

@@ -50,6 +50,18 @@ func filterImages(images []*Image, filters []filterFunc) ([]*Image, error) {
 func (r *Runtime) compileImageFilters(ctx context.Context, options *ListImagesOptions) ([]filterFunc, error) {
 	logrus.Tracef("Parsing image filters %s", options.Filters)
 
+	var tree *layerTree
+	getTree := func() (*layerTree, error) {
+		if tree == nil {
+			t, err := r.layerTree()
+			if err != nil {
+				return nil, err
+			}
+			tree = t
+		}
+		return tree, nil
+	}
+
 	filterFuncs := []filterFunc{}
 	for _, filter := range options.Filters {
 		var key, value string
@@ -93,7 +105,11 @@ func (r *Runtime) compileImageFilters(ctx context.Context, options *ListImagesOp
 			if err != nil {
 				return nil, errors.Wrapf(err, "non-boolean value %q for dangling filter", value)
 			}
-			filterFuncs = append(filterFuncs, filterDangling(ctx, dangling))
+			t, err := getTree()
+			if err != nil {
+				return nil, err
+			}
+			filterFuncs = append(filterFuncs, filterDangling(ctx, dangling, t))
 
 		case "id":
 			filterFuncs = append(filterFuncs, filterID(value))
@@ -103,7 +119,11 @@ func (r *Runtime) compileImageFilters(ctx context.Context, options *ListImagesOp
 			if err != nil {
 				return nil, errors.Wrapf(err, "non-boolean value %q for intermediate filter", value)
 			}
-			filterFuncs = append(filterFuncs, filterIntermediate(ctx, intermediate))
+			t, err := getTree()
+			if err != nil {
+				return nil, err
+			}
+			filterFuncs = append(filterFuncs, filterIntermediate(ctx, intermediate, t))
 
 		case "label":
 			filterFuncs = append(filterFuncs, filterLabel(ctx, value))
@@ -221,9 +241,9 @@ func filterContainers(value string, fn IsExternalContainerFunc) filterFunc {
 }
 
 // filterDangling creates a dangling filter for matching the specified value.
-func filterDangling(ctx context.Context, value bool) filterFunc {
+func filterDangling(ctx context.Context, value bool, tree *layerTree) filterFunc {
 	return func(img *Image) (bool, error) {
-		isDangling, err := img.IsDangling(ctx)
+		isDangling, err := img.isDangling(ctx, tree)
 		if err != nil {
 			return false, err
 		}
@@ -241,9 +261,9 @@ func filterID(value string) filterFunc {
 // filterIntermediate creates an intermediate filter for images.  An image is
 // considered to be an intermediate image if it is dangling (i.e., no tags) and
 // has no children (i.e., no other image depends on it).
-func filterIntermediate(ctx context.Context, value bool) filterFunc {
+func filterIntermediate(ctx context.Context, value bool, tree *layerTree) filterFunc {
 	return func(img *Image) (bool, error) {
-		isIntermediate, err := img.IsIntermediate(ctx)
+		isIntermediate, err := img.isIntermediate(ctx, tree)
 		if err != nil {
 			return false, err
 		}

libimage/image.go

@@ -128,10 +128,16 @@ func (i *Image) IsReadOnly() bool {
 // IsDangling returns true if the image is dangling, that is an untagged image
 // without children.
 func (i *Image) IsDangling(ctx context.Context) (bool, error) {
+	return i.isDangling(ctx, nil)
+}
+
+// isDangling returns true if the image is dangling, that is an untagged image
+// without children.  If tree is nil, it will created for this invocation only.
+func (i *Image) isDangling(ctx context.Context, tree *layerTree) (bool, error) {
 	if len(i.Names()) > 0 {
 		return false, nil
 	}
-	children, err := i.getChildren(ctx, false)
+	children, err := i.getChildren(ctx, false, nil)
 	if err != nil {
 		return false, err
 	}
@@ -141,10 +147,17 @@ func (i *Image) IsDangling(ctx context.Context) (bool, error) {
 // IsIntermediate returns true if the image is an intermediate image, that is
 // an untagged image with children.
 func (i *Image) IsIntermediate(ctx context.Context) (bool, error) {
+	return i.isIntermediate(ctx, nil)
+}
+
+// isIntermediate returns true if the image is an intermediate image, that is
+// an untagged image with children.  If tree is nil, it will created for this
+// invocation only.
+func (i *Image) isIntermediate(ctx context.Context, tree *layerTree) (bool, error) {
 	if len(i.Names()) > 0 {
 		return false, nil
 	}
-	children, err := i.getChildren(ctx, false)
+	children, err := i.getChildren(ctx, false, tree)
 	if err != nil {
 		return false, err
 	}
@@ -189,7 +202,7 @@ func (i *Image) Parent(ctx context.Context) (*Image, error) {
 
 // HasChildren returns indicates if the image has children.
 func (i *Image) HasChildren(ctx context.Context) (bool, error) {
-	children, err := i.getChildren(ctx, false)
+	children, err := i.getChildren(ctx, false, nil)
 	if err != nil {
 		return false, err
 	}
@@ -198,21 +211,24 @@ func (i *Image) HasChildren(ctx context.Context) (bool, error) {
 
 // Children returns the image's children.
 func (i *Image) Children(ctx context.Context) ([]*Image, error) {
-	children, err := i.getChildren(ctx, true)
+	children, err := i.getChildren(ctx, true, nil)
 	if err != nil {
 		return nil, err
 	}
 	return children, nil
 }
 
 // getChildren returns a list of imageIDs that depend on the image. If all is
-// false, only the first child image is returned.
-func (i *Image) getChildren(ctx context.Context, all bool) ([]*Image, error) {
-	tree, err := i.runtime.layerTree()
-	if err != nil {
-		return nil, err
+// false, only the first child image is returned.  If tree is nil, it will be
+// created for this invocation only.
+func (i *Image) getChildren(ctx context.Context, all bool, tree *layerTree) ([]*Image, error) {
+	if tree == nil {
+		t, err := i.runtime.layerTree()
+		if err != nil {
+			return nil, err
+		}
+		tree = t
 	}
-
 	return tree.children(ctx, i, all)
 }