From af6b87672fa55a2436609ac63bd19931d3fe7725 Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Wed, 15 Jun 2022 00:00:28 -0600
Subject: do a better job of scanning for mapping stuff in a device

---
 pkg/btrfsmisc/walk.go | 110 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 pkg/btrfsmisc/walk.go

(limited to 'pkg/btrfsmisc')

diff --git a/pkg/btrfsmisc/walk.go b/pkg/btrfsmisc/walk.go
new file mode 100644
index 0000000..fc0edbc
--- /dev/null
+++ b/pkg/btrfsmisc/walk.go
@@ -0,0 +1,110 @@
+package btrfsmisc
+
+import (
+	"fmt"
+
+	"lukeshu.com/btrfs-tools/pkg/btrfs"
+	"lukeshu.com/btrfs-tools/pkg/btrfs/btrfsitem"
+	"lukeshu.com/btrfs-tools/pkg/util"
+)
+
+type WalkErr struct {
+	TreeName string
+	Path     btrfs.WalkTreePath
+	Err      error
+}
+
+func (e WalkErr) Unwrap() error { return e.Err }
+
+func (e WalkErr) Error() string {
+	if len(e.Path) == 0 {
+		return fmt.Sprintf("%v: %v", e.TreeName, e.Err)
+	}
+	return fmt.Sprintf("%v: %v: %v", e.TreeName, e.Path, e.Err)
+}
+
+// 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)) {
+	var treeName string
+	handleErr := func(path btrfs.WalkTreePath, err error) {
+		errCb(WalkErr{
+			TreeName: treeName,
+			Path:     path,
+			Err:      err,
+		})
+	}
+
+	var foundTrees []struct {
+		Name string
+		Root btrfs.LogicalAddr
+	}
+	origItem := cbs.Item
+	cbs.Item = func(path btrfs.WalkTreePath, item btrfs.Item) error {
+		if item.Head.Key.ItemType == btrfsitem.ROOT_ITEM_KEY {
+			root, ok := item.Body.(btrfsitem.Root)
+			if !ok {
+				handleErr(path, fmt.Errorf("ROOT_ITEM_KEY is a %T, not a btrfsitem.Root", item.Body))
+			} else {
+				foundTrees = append(foundTrees, struct {
+					Name string
+					Root btrfs.LogicalAddr
+				}{
+					Name: fmt.Sprintf("tree %v (via %v %v)",
+						item.Head.Key.ObjectID.Format(0), treeName, path),
+					Root: root.ByteNr,
+				})
+			}
+		}
+		if origItem != nil {
+			return origItem(path, item)
+		}
+		return nil
+	}
+
+	origNode := cbs.Node
+	cbs.Node = func(path btrfs.WalkTreePath, node *util.Ref[btrfs.LogicalAddr, btrfs.Node], err error) error {
+		if err != nil {
+			handleErr(path, err)
+		}
+		if node != nil && origNode != nil {
+			return origNode(path, node, nil)
+		}
+		return nil
+	}
+
+	treeName = "superblock"
+	superblock, err := fs.Superblock()
+	if err != nil {
+		handleErr(nil, err)
+		return
+	}
+
+	treeName = "root tree"
+	if err := fs.WalkTree(superblock.Data.RootTree, cbs); err != nil {
+		handleErr(nil, err)
+	}
+
+	treeName = "chunk tree"
+	if err := fs.WalkTree(superblock.Data.ChunkTree, cbs); err != nil {
+		handleErr(nil, err)
+	}
+
+	treeName = "log tree"
+	if err := fs.WalkTree(superblock.Data.LogTree, cbs); err != nil {
+		handleErr(nil, err)
+	}
+
+	treeName = "block group tree"
+	if err := fs.WalkTree(superblock.Data.BlockGroupRoot, cbs); err != nil {
+		handleErr(nil, err)
+	}
+
+	for _, tree := range foundTrees {
+		treeName = tree.Name
+		if err := fs.WalkTree(tree.Root, cbs); err != nil {
+			handleErr(nil, err)
+		}
+	}
+}
-- 
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