From b589943af25661c140bacdc0afc2550e1e2db852 Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Fri, 1 Jul 2022 00:31:57 -0600
Subject: add more callbacks to WalkFS

---
 cmd/btrfs-fsck/pass1.go | 27 +++++++++++++++------------
 cmd/btrfs-fsck/pass2.go | 15 +++++++++------
 pkg/btrfsmisc/walk.go   | 33 ++++++++++++++++++++++++++-------
 3 files changed, 50 insertions(+), 25 deletions(-)

diff --git a/cmd/btrfs-fsck/pass1.go b/cmd/btrfs-fsck/pass1.go
index 6812c73..5188d65 100644
--- a/cmd/btrfs-fsck/pass1.go
+++ b/cmd/btrfs-fsck/pass1.go
@@ -22,19 +22,22 @@ func pass1(fs *btrfs.FS, superblock *util.Ref[btrfs.PhysicalAddr, btrfs.Superblo
 
 	fmt.Printf("Pass 1: ... walking fs\n")
 	visitedNodes := make(map[btrfs.LogicalAddr]struct{})
-	btrfsmisc.WalkFS(fs, btrfs.WalkTreeHandler{
-		Node: func(path btrfs.WalkTreePath, node *util.Ref[btrfs.LogicalAddr, btrfs.Node], err error) error {
-			if err != nil {
-				err = fmt.Errorf("%v: %w", path, err)
-				fmt.Printf("Pass 1: ... walk fs: error: %v\n", err)
-			}
-			if node != nil {
-				visitedNodes[node.Addr] = struct{}{}
-			}
-			return err
+	btrfsmisc.WalkFS(fs, btrfsmisc.WalkFSHandler{
+		WalkTreeHandler: btrfs.WalkTreeHandler{
+			Node: func(path btrfs.WalkTreePath, node *util.Ref[btrfs.LogicalAddr, btrfs.Node], err error) error {
+				if err != nil {
+					err = fmt.Errorf("%v: %w", path, err)
+					fmt.Printf("Pass 1: ... walk fs: error: %v\n", err)
+				}
+				if node != nil {
+					visitedNodes[node.Addr] = struct{}{}
+				}
+				return err
+			},
+		},
+		Err: func(err error) {
+			fmt.Printf("Pass 1: ... walk fs: error: %v\n", err)
 		},
-	}, func(err error) {
-		fmt.Printf("Pass 1: ... walk fs: error: %v\n", err)
 	})
 
 	fsFoundNodes := make(map[btrfs.LogicalAddr]struct{})
diff --git a/cmd/btrfs-fsck/pass2.go b/cmd/btrfs-fsck/pass2.go
index acea740..7970cca 100644
--- a/cmd/btrfs-fsck/pass2.go
+++ b/cmd/btrfs-fsck/pass2.go
@@ -13,13 +13,16 @@ func pass2(fs *btrfs.FS, foundNodes map[btrfs.LogicalAddr]struct{}) {
 	fmt.Printf("\nPass 2: orphaned nodes\n")
 
 	visitedNodes := make(map[btrfs.LogicalAddr]struct{})
-	btrfsmisc.WalkFS(fs, btrfs.WalkTreeHandler{
-		Node: func(path btrfs.WalkTreePath, node *util.Ref[btrfs.LogicalAddr, btrfs.Node], err error) error {
-			visitedNodes[node.Addr] = struct{}{}
-			return nil
+	btrfsmisc.WalkFS(fs, btrfsmisc.WalkFSHandler{
+		WalkTreeHandler: btrfs.WalkTreeHandler{
+			Node: func(path btrfs.WalkTreePath, node *util.Ref[btrfs.LogicalAddr, btrfs.Node], err error) error {
+				visitedNodes[node.Addr] = struct{}{}
+				return nil
+			},
+		},
+		Err: func(err error) {
+			fmt.Printf("Pass 2: walk FS: error: %v\n", err)
 		},
-	}, func(err error) {
-		fmt.Printf("Pass 2: walk FS: error: %v\n", err)
 	})
 
 	orphanedNodes := make(map[btrfs.LogicalAddr]int)
diff --git a/pkg/btrfsmisc/walk.go b/pkg/btrfsmisc/walk.go
index fc0edbc..a82bd5f 100644
--- a/pkg/btrfsmisc/walk.go
+++ b/pkg/btrfsmisc/walk.go
@@ -23,13 +23,22 @@ func (e WalkErr) Error() string {
 	return fmt.Sprintf("%v: %v: %v", e.TreeName, e.Path, e.Err)
 }
 
+type WalkFSHandler struct {
+	Err func(error)
+	// Callbacks for entire trees
+	PreTree  func(name string, laddr btrfs.LogicalAddr)
+	PostTree func(name string, laddr btrfs.LogicalAddr)
+	// Callbacks for nodes or smaller
+	btrfs.WalkTreeHandler
+}
+
 // WalkFS walks all trees in a *btrfs.FS.  Rather than returning an
 // error, it calls errCb each time an error is encountered.  The error
 // will always be of type WalkErr.
-func WalkFS(fs *btrfs.FS, cbs btrfs.WalkTreeHandler, errCb func(error)) {
+func WalkFS(fs *btrfs.FS, cbs WalkFSHandler) {
 	var treeName string
 	handleErr := func(path btrfs.WalkTreePath, err error) {
-		errCb(WalkErr{
+		cbs.Err(WalkErr{
 			TreeName: treeName,
 			Path:     path,
 			Err:      err,
@@ -82,29 +91,39 @@ func WalkFS(fs *btrfs.FS, cbs btrfs.WalkTreeHandler, errCb func(error)) {
 	}
 
 	treeName = "root tree"
-	if err := fs.WalkTree(superblock.Data.RootTree, cbs); err != nil {
+	cbs.PreTree(treeName, superblock.Data.RootTree)
+	if err := fs.WalkTree(superblock.Data.RootTree, cbs.WalkTreeHandler); err != nil {
 		handleErr(nil, err)
 	}
+	cbs.PostTree(treeName, superblock.Data.RootTree)
 
 	treeName = "chunk tree"
-	if err := fs.WalkTree(superblock.Data.ChunkTree, cbs); err != nil {
+	cbs.PreTree(treeName, superblock.Data.ChunkTree)
+	if err := fs.WalkTree(superblock.Data.ChunkTree, cbs.WalkTreeHandler); err != nil {
 		handleErr(nil, err)
 	}
+	cbs.PostTree(treeName, superblock.Data.ChunkTree)
 
 	treeName = "log tree"
-	if err := fs.WalkTree(superblock.Data.LogTree, cbs); err != nil {
+	cbs.PreTree(treeName, superblock.Data.LogTree)
+	if err := fs.WalkTree(superblock.Data.LogTree, cbs.WalkTreeHandler); err != nil {
 		handleErr(nil, err)
 	}
+	cbs.PostTree(treeName, superblock.Data.LogTree)
 
 	treeName = "block group tree"
-	if err := fs.WalkTree(superblock.Data.BlockGroupRoot, cbs); err != nil {
+	cbs.PreTree(treeName, superblock.Data.BlockGroupRoot)
+	if err := fs.WalkTree(superblock.Data.BlockGroupRoot, cbs.WalkTreeHandler); err != nil {
 		handleErr(nil, err)
 	}
+	cbs.PostTree(treeName, superblock.Data.BlockGroupRoot)
 
 	for _, tree := range foundTrees {
 		treeName = tree.Name
-		if err := fs.WalkTree(tree.Root, cbs); err != nil {
+		cbs.PreTree(treeName, tree.Root)
+		if err := fs.WalkTree(tree.Root, cbs.WalkTreeHandler); err != nil {
 			handleErr(nil, err)
 		}
+		cbs.PostTree(treeName, tree.Root)
 	}
 }
-- 
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