Merge branch 'lukeshu/tree-api-pt1-changes'

13 files changed, 88 insertions, 56 deletions

diff --git a/cmd/btrfs-rec/inspect/lsfiles/lsfiles.go b/cmd/btrfs-rec/inspect/lsfiles/lsfiles.go
index a713b8a..e42050f 100644
--- a/cmd/btrfs-rec/inspect/lsfiles/lsfiles.go
+++ b/cmd/btrfs-rec/inspect/lsfiles/lsfiles.go
@@ -8,6 +8,7 @@
 package lsfiles
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"io"
@@ -27,6 +28,7 @@ import (
 )
 
 func LsFiles(
+	ctx context.Context,
 	out io.Writer,
 	fs interface {
 		btrfstree.TreeOperator
@@ -42,6 +44,7 @@ func LsFiles(
 	}()
 
 	printSubvol(out, "", true, "/", btrfs.NewSubvolume(
+		ctx,
 		fs,
 		btrfsprim.FS_TREE_OBJECTID,
 		false,
diff --git a/cmd/btrfs-rec/inspect/mount/mount.go b/cmd/btrfs-rec/inspect/mount/mount.go
index 4049393..d4d2e0a 100644
--- a/cmd/btrfs-rec/inspect/mount/mount.go
+++ b/cmd/btrfs-rec/inspect/mount/mount.go
@@ -53,6 +53,7 @@ func MountRO(ctx context.Context, fs *btrfs.FS, mountpoint string, noChecksums b
 
 	rootSubvol := &subvolume{
 		Subvolume: btrfs.NewSubvolume(
+			ctx,
 			btrfsutil.NewOldRebuiltForrest(ctx, fs),
 			btrfsprim.FS_TREE_OBJECTID,
 			noChecksums,
diff --git a/cmd/btrfs-rec/inspect_lsfiles.go b/cmd/btrfs-rec/inspect_lsfiles.go
index 04b5ec5..00a4873 100644
--- a/cmd/btrfs-rec/inspect_lsfiles.go
+++ b/cmd/btrfs-rec/inspect_lsfiles.go
@@ -30,6 +30,7 @@ func init() {
 			}()
 
 			return lsfiles.LsFiles(
+				cmd.Context(),
 				out,
 				btrfsutil.NewOldRebuiltForrest(cmd.Context(), fs))
 		}),
diff --git a/lib/btrfs/btrfsitem/item_root.go b/lib/btrfs/btrfsitem/item_root.go
index 4ffad9a..8bdc3df 100644
--- a/lib/btrfs/btrfsitem/item_root.go
+++ b/lib/btrfs/btrfsitem/item_root.go
@@ -22,6 +22,11 @@ import (
 //	key.offset   = one of:
 //	   - 0 if objectid is one of the BTRFS_*_TREE_OBJECTID defines or a non-snapshot volume; or
 //	   - transaction_id of when this snapshot was created
+//
+// This tree might contain nodes with node.Head.Owner set to the
+// root.ParentUUID tree, *if* the node.Head.Generation is
+// less-than-or-equal-to the root's key.offset.  The "or-equal-to"
+// part of that might be surprising, which is why I called it out.
 type Root struct { // trivial ROOT_ITEM=132
 	Inode         Inode                `bin:"off=0x000, siz=0xa0"` // ???
 	Generation    btrfsprim.Generation `bin:"off=0x0a0, siz=0x08"`
diff --git a/lib/btrfs/btrfstree/btree_forrest.go b/lib/btrfs/btrfstree/btree_forrest.go
index 8f8e2de..38a2721 100644
--- a/lib/btrfs/btrfstree/btree_forrest.go
+++ b/lib/btrfs/btrfstree/btree_forrest.go
@@ -21,6 +21,8 @@ type TreeRoot struct {
 	RootNode   btrfsvol.LogicalAddr
 	Level      uint8
 	Generation btrfsprim.Generation
+
+	RootInode btrfsprim.ObjID // only for subvolume trees
 }
 
 // LookupTreeRoot is a utility function to help with implementing the
@@ -59,7 +61,7 @@ func LookupTreeRoot(_ context.Context, fs TreeOperator, sb Superblock, treeID bt
 		rootItem, err := fs.TreeSearch(btrfsprim.ROOT_TREE_OBJECTID, SearchRootItem(treeID))
 		if err != nil {
 			if errors.Is(err, ErrNoItem) {
-				err = ErrNoTree
+				err = fmt.Errorf("%w: %s", ErrNoTree, err)
 			}
 			return nil, fmt.Errorf("tree %s: %w", treeID.Format(btrfsprim.ROOT_TREE_OBJECTID), err)
 		}
@@ -70,6 +72,7 @@ func LookupTreeRoot(_ context.Context, fs TreeOperator, sb Superblock, treeID bt
 				RootNode:   rootItemBody.ByteNr,
 				Level:      rootItemBody.Level,
 				Generation: rootItemBody.Generation,
+				RootInode:  rootItemBody.RootDirID,
 			}, nil
 		case *btrfsitem.Error:
 			return nil, fmt.Errorf("malformed ROOT_ITEM for tree %v: %w", treeID, rootItemBody.Err)
diff --git a/lib/btrfs/btrfstree/readnode.go b/lib/btrfs/btrfstree/readnode.go
index c2e3b0f..ac82c62 100644
--- a/lib/btrfs/btrfstree/readnode.go
+++ b/lib/btrfs/btrfstree/readnode.go
@@ -20,13 +20,13 @@ type NodeFile interface {
 	// ParentTree, given a tree ID, returns that tree's parent
 	// tree, if it has one.
 	//
-	//  - non-zero, true : the parent tree ID
+	//  - non-zero, ?, true : the parent tree ID
 	//
-	//  - 0, true : the tree does not have a parent
+	//  - 0, 0, true : the tree does not have a parent
 	//
-	//  - any, false : the tree's parent information could not be
+	//  - ?, ?, false : the tree's parent information could not be
 	//    looked up
-	ParentTree(btrfsprim.ObjID) (btrfsprim.ObjID, bool)
+	ParentTree(btrfsprim.ObjID) (btrfsprim.ObjID, btrfsprim.Generation, bool)
 }
 
 // FSReadNode is a utility function to help with implementing the
@@ -40,25 +40,33 @@ func FSReadNode(
 		return nil, fmt.Errorf("btrfs.FS.ReadNode: %w", err)
 	}
 
-	var treeParents []btrfsprim.ObjID
-	checkOwner := func(owner btrfsprim.ObjID) error {
-		exp := path.Node(-1).FromTree
+	checkOwner := func(owner btrfsprim.ObjID, gen btrfsprim.Generation) error {
+		var treeParents []btrfsprim.ObjID
+
+		tree := path.Node(-1).FromTree
 		for {
-			if owner == exp {
+			if owner == tree {
+				// OK!
 				return nil
 			}
-			treeParents = append(treeParents, exp)
-			var ok bool
-			exp, ok = fs.ParentTree(exp)
-			if !ok {
+
+			treeParents = append(treeParents, tree)
+			parent, parentGen, parentOK := fs.ParentTree(tree)
+			if !parentOK {
 				// Failed look up parent info; fail open.
 				return nil
 			}
-			if exp == 0 {
+
+			if parent == 0 {
 				// End of the line.
 				return fmt.Errorf("expected owner in %v but claims to have owner=%v",
 					treeParents, owner)
 			}
+			if gen > parentGen {
+				return fmt.Errorf("claimed owner=%v might be acceptable in this tree (if generation<=%v) but not with claimed generation=%v",
+					owner, parentGen, gen)
+			}
+			tree = parent
 		}
 	}
 
diff --git a/lib/btrfs/btrfstree/types_node.go b/lib/btrfs/btrfstree/types_node.go
index 622f23c..bfcbbf4 100644
--- a/lib/btrfs/btrfstree/types_node.go
+++ b/lib/btrfs/btrfstree/types_node.go
@@ -417,7 +417,7 @@ type NodeExpectations struct {
 	// Things knowable from the parent.
 	Level      containers.Optional[uint8]
 	Generation containers.Optional[btrfsprim.Generation]
-	Owner      func(btrfsprim.ObjID) error
+	Owner      func(btrfsprim.ObjID, btrfsprim.Generation) error
 	MinItem    containers.Optional[btrfsprim.Key]
 	// Things knowable from the structure of the tree.
 	MaxItem containers.Optional[btrfsprim.Key]
@@ -547,7 +547,7 @@ func (exp NodeExpectations) Check(node *Node) error {
 			exp.Generation.Val, node.Head.Generation))
 	}
 	if exp.Owner != nil {
-		if err := exp.Owner(node.Head.Owner); err != nil {
+		if err := exp.Owner(node.Head.Owner, node.Head.Generation); err != nil {
 			errs = append(errs, err)
 		}
 	}
diff --git a/lib/btrfs/io2_lv.go b/lib/btrfs/io2_lv.go
index 9f4e53f..03b2107 100644
--- a/lib/btrfs/io2_lv.go
+++ b/lib/btrfs/io2_lv.go
@@ -27,9 +27,8 @@ type FS struct {
 	cacheSuperblocks []*diskio.Ref[btrfsvol.PhysicalAddr, btrfstree.Superblock]
 	cacheSuperblock  *btrfstree.Superblock
 
-	cacheObjID2UUID map[btrfsprim.ObjID]btrfsprim.UUID
+	cacheObjID2All  map[btrfsprim.ObjID]treeInfo
 	cacheUUID2ObjID map[btrfsprim.UUID]btrfsprim.ObjID
-	cacheTreeParent map[btrfsprim.ObjID]btrfsprim.UUID
 }
 
 var _ diskio.File[btrfsvol.LogicalAddr] = (*FS)(nil)
diff --git a/lib/btrfs/io3_btree.go b/lib/btrfs/io3_btree.go
index 6df88f5..b60f54a 100644
--- a/lib/btrfs/io3_btree.go
+++ b/lib/btrfs/io3_btree.go
@@ -25,13 +25,18 @@ var _ btrfstree.NodeSource = (*FS)(nil)
 
 // btrfstree.NodeFile //////////////////////////////////////////////////////////
 
+type treeInfo struct {
+	UUID       btrfsprim.UUID
+	ParentUUID btrfsprim.UUID
+	ParentGen  btrfsprim.Generation
+}
+
 func (fs *FS) populateTreeUUIDs(ctx context.Context) {
-	if fs.cacheObjID2UUID != nil && fs.cacheUUID2ObjID != nil && fs.cacheTreeParent != nil {
+	if fs.cacheObjID2All != nil && fs.cacheUUID2ObjID != nil {
 		return
 	}
-	fs.cacheObjID2UUID = make(map[btrfsprim.ObjID]btrfsprim.UUID)
+	fs.cacheObjID2All = make(map[btrfsprim.ObjID]treeInfo)
 	fs.cacheUUID2ObjID = make(map[btrfsprim.UUID]btrfsprim.ObjID)
-	fs.cacheTreeParent = make(map[btrfsprim.ObjID]btrfsprim.UUID)
 	fs.TreeWalk(ctx, btrfsprim.ROOT_TREE_OBJECTID,
 		func(err *btrfstree.TreeError) {
 			// do nothing
@@ -42,8 +47,11 @@ func (fs *FS) populateTreeUUIDs(ctx context.Context) {
 				if !ok {
 					return
 				}
-				fs.cacheObjID2UUID[item.Key.ObjectID] = itemBody.UUID
-				fs.cacheTreeParent[item.Key.ObjectID] = itemBody.ParentUUID
+				fs.cacheObjID2All[item.Key.ObjectID] = treeInfo{
+					UUID:       itemBody.UUID,
+					ParentUUID: itemBody.ParentUUID,
+					ParentGen:  btrfsprim.Generation(item.Key.Offset),
+				}
 				fs.cacheUUID2ObjID[itemBody.UUID] = item.Key.ObjectID
 			},
 		},
@@ -51,27 +59,28 @@ func (fs *FS) populateTreeUUIDs(ctx context.Context) {
 }
 
 // ParentTree implements btrfstree.NodeFile.
-func (fs *FS) ParentTree(tree btrfsprim.ObjID) (btrfsprim.ObjID, bool) {
+func (fs *FS) ParentTree(tree btrfsprim.ObjID) (btrfsprim.ObjID, btrfsprim.Generation, bool) {
 	if tree < btrfsprim.FIRST_FREE_OBJECTID || tree > btrfsprim.LAST_FREE_OBJECTID {
 		// no parent
-		return 0, true
+		return 0, 0, true
 	}
 	fs.populateTreeUUIDs(context.TODO())
-	parentUUID, ok := fs.cacheTreeParent[tree]
+
+	all, ok := fs.cacheObjID2All[tree]
 	if !ok {
 		// could not look up parent info
-		return 0, false
+		return 0, 0, false
 	}
-	if parentUUID == (btrfsprim.UUID{}) {
+	if all.ParentUUID == (btrfsprim.UUID{}) {
 		// no parent
-		return 0, true
+		return 0, 0, true
 	}
-	parentObjID, ok := fs.cacheUUID2ObjID[parentUUID]
+	parentObjID, ok := fs.cacheUUID2ObjID[all.ParentUUID]
 	if !ok {
 		// could not look up parent info
-		return 0, false
+		return 0, 0, false
 	}
-	return parentObjID, true
+	return parentObjID, all.ParentGen, true
 }
 
 var _ btrfstree.NodeFile = (*FS)(nil)
diff --git a/lib/btrfs/io4_fs.go b/lib/btrfs/io4_fs.go
index 0445441..4a68695 100644
--- a/lib/btrfs/io4_fs.go
+++ b/lib/btrfs/io4_fs.go
@@ -5,6 +5,7 @@
 package btrfs
 
 import (
+	"context"
 	"fmt"
 	"io"
 	"path/filepath"
@@ -62,7 +63,8 @@ type File struct {
 }
 
 type Subvolume struct {
-	fs interface {
+	ctx context.Context //nolint:containedctx // don't have an option while keeping the same API
+	fs  interface {
 		btrfstree.TreeOperator
 		Superblock() (*btrfstree.Superblock, error)
 		diskio.ReaderAt[btrfsvol.LogicalAddr]
@@ -70,8 +72,8 @@ type Subvolume struct {
 	TreeID      btrfsprim.ObjID
 	noChecksums bool
 
-	rootVal btrfsitem.Root
-	rootErr error
+	rootInfo btrfstree.TreeRoot
+	rootErr  error
 
 	bareInodeCache containers.ARCache[btrfsprim.ObjID, *BareInode]
 	fullInodeCache containers.ARCache[btrfsprim.ObjID, *FullInode]
@@ -80,6 +82,7 @@ type Subvolume struct {
 }
 
 func NewSubvolume(
+	ctx context.Context,
 	fs interface {
 		btrfstree.TreeOperator
 		Superblock() (*btrfstree.Superblock, error)
@@ -94,19 +97,17 @@ func NewSubvolume(
 		noChecksums: noChecksums,
 	}
 
-	root, err := sv.fs.TreeSearch(btrfsprim.ROOT_TREE_OBJECTID, btrfstree.SearchRootItem(sv.TreeID))
+	sb, err := sv.fs.Superblock()
 	if err != nil {
 		sv.rootErr = err
-	} else {
-		switch rootBody := root.Body.(type) {
-		case *btrfsitem.Root:
-			sv.rootVal = rootBody.Clone()
-		case *btrfsitem.Error:
-			sv.rootErr = fmt.Errorf("FS_TREE ROOT_ITEM has malformed body: %w", rootBody.Err)
-		default:
-			panic(fmt.Errorf("should not happen: ROOT_ITEM has unexpected item type: %T", rootBody))
-		}
+		return sv
+	}
+	rootInfo, err := btrfstree.LookupTreeRoot(ctx, sv.fs, *sb, sv.TreeID)
+	if err != nil {
+		sv.rootErr = err
+		return sv
 	}
+	sv.rootInfo = *rootInfo
 
 	sv.bareInodeCache.MaxLen = textui.Tunable(128)
 	sv.fullInodeCache.MaxLen = textui.Tunable(128)
@@ -117,11 +118,11 @@ func NewSubvolume(
 }
 
 func (sv *Subvolume) NewChildSubvolume(childID btrfsprim.ObjID) *Subvolume {
-	return NewSubvolume(sv.fs, childID, sv.noChecksums)
+	return NewSubvolume(sv.ctx, sv.fs, childID, sv.noChecksums)
 }
 
 func (sv *Subvolume) GetRootInode() (btrfsprim.ObjID, error) {
-	return sv.rootVal.RootDirID, sv.rootErr
+	return sv.rootInfo.RootInode, sv.rootErr
 }
 
 func (sv *Subvolume) LoadBareInode(inode btrfsprim.ObjID) (*BareInode, error) {
diff --git a/lib/btrfsutil/old_rebuilt_forrest.go b/lib/btrfsutil/old_rebuilt_forrest.go
index bb5ab59..5b99892 100644
--- a/lib/btrfsutil/old_rebuilt_forrest.go
+++ b/lib/btrfsutil/old_rebuilt_forrest.go
@@ -240,10 +240,11 @@ func (bt *OldRebuiltForrest) readNode(nodeInfo nodeInfo) *btrfstree.Node {
 		LAddr:      containers.OptionalValue(nodeInfo.LAddr),
 		Level:      containers.OptionalValue(nodeInfo.Level),
 		Generation: containers.OptionalValue(nodeInfo.Generation),
-		Owner: func(treeID btrfsprim.ObjID) error {
-			if treeID != nodeInfo.Owner {
-				return fmt.Errorf("expected owner=%v but claims to have owner=%v",
-					nodeInfo.Owner, treeID)
+		Owner: func(treeID btrfsprim.ObjID, gen btrfsprim.Generation) error {
+			if treeID != nodeInfo.Owner || gen != nodeInfo.Generation {
+				return fmt.Errorf("expected owner=%v generation=%v but claims to have owner=%v generation=%v",
+					nodeInfo.Owner, nodeInfo.Generation,
+					treeID, gen)
 			}
 			return nil
 		},
diff --git a/lib/btrfsutil/rebuilt_readitem.go b/lib/btrfsutil/rebuilt_readitem.go
index ff919f0..03a7cdc 100644
--- a/lib/btrfsutil/rebuilt_readitem.go
+++ b/lib/btrfsutil/rebuilt_readitem.go
@@ -42,10 +42,11 @@ func (ts *RebuiltForrest) readNode(ctx context.Context, laddr btrfsvol.LogicalAd
 		LAddr:      containers.OptionalValue(laddr),
 		Level:      containers.OptionalValue(graphInfo.Level),
 		Generation: containers.OptionalValue(graphInfo.Generation),
-		Owner: func(treeID btrfsprim.ObjID) error {
-			if treeID != graphInfo.Owner {
-				return fmt.Errorf("expected owner=%v but claims to have owner=%v",
-					graphInfo.Owner, treeID)
+		Owner: func(treeID btrfsprim.ObjID, gen btrfsprim.Generation) error {
+			if treeID != graphInfo.Owner || gen != graphInfo.Generation {
+				return fmt.Errorf("expected owner=%v generation=%v but claims to have owner=%v generation=%v",
+					graphInfo.Owner, graphInfo.Generation,
+					treeID, gen)
 			}
 			return nil
 		},
diff --git a/lib/btrfsutil/rebuilt_tree.go b/lib/btrfsutil/rebuilt_tree.go
index 3fff9b2..96d5a75 100644
--- a/lib/btrfsutil/rebuilt_tree.go
+++ b/lib/btrfsutil/rebuilt_tree.go
@@ -122,7 +122,7 @@ func (tree *RebuiltTree) isOwnerOK(owner btrfsprim.ObjID, gen btrfsprim.Generati
 		if owner == tree.ID {
 			return true
 		}
-		if tree.Parent == nil || gen >= tree.ParentGen {
+		if tree.Parent == nil || gen > tree.ParentGen {
 			return false
 		}
 		tree = tree.Parent