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// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package btrfstree
import (
"context"
"errors"
"fmt"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsitem"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsprim"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
)
// LookupTreeRoot //////////////////////////////////////////////////////////////
// A TreeRoot is more-or-less a btrfsitem.Root, but simpler; returned by
// LookupTreeRoot.
type TreeRoot struct {
ID btrfsprim.ObjID
RootNode btrfsvol.LogicalAddr
Level uint8
Generation btrfsprim.Generation
RootInode btrfsprim.ObjID // only for subvolume trees
ParentUUID btrfsprim.UUID
ParentGen btrfsprim.Generation // offset of this tree's root item
}
// LookupTreeRoot is a utility function to help with implementing the
// 'Forrest' interface.
//
// The 'forrest' passed to LookupTreeRoot must handle:
//
// forrest.ForrestLookup(ctx, btrfsprim.ROOT_TREE_OBJECTID)
//
// It is OK for forrest.ForrestLookup to recurse and call
// LookupTreeRoot, as LookupTreeRoot will not call ForrestLookup for
// ROOT_TREE_OBJECTID; so it will not be an infinite recursion.
func LookupTreeRoot(ctx context.Context, forrest Forrest, sb Superblock, treeID btrfsprim.ObjID) (*TreeRoot, error) {
switch treeID {
case btrfsprim.ROOT_TREE_OBJECTID:
return &TreeRoot{
ID: treeID,
RootNode: sb.RootTree,
Level: sb.RootLevel,
Generation: sb.Generation, // XXX: same generation as LOG_TREE?
}, nil
case btrfsprim.CHUNK_TREE_OBJECTID:
return &TreeRoot{
ID: treeID,
RootNode: sb.ChunkTree,
Level: sb.ChunkLevel,
Generation: sb.ChunkRootGeneration,
}, nil
case btrfsprim.TREE_LOG_OBJECTID:
return &TreeRoot{
ID: treeID,
RootNode: sb.LogTree,
Level: sb.LogLevel,
Generation: sb.Generation, // XXX: same generation as ROOT_TREE?
}, nil
case btrfsprim.BLOCK_GROUP_TREE_OBJECTID:
return &TreeRoot{
ID: treeID,
RootNode: sb.BlockGroupRoot,
Level: sb.BlockGroupRootLevel,
Generation: sb.BlockGroupRootGeneration,
}, nil
default:
rootTree, err := forrest.ForrestLookup(ctx, btrfsprim.ROOT_TREE_OBJECTID)
if err != nil {
return nil, fmt.Errorf("tree %s: %w", treeID.Format(btrfsprim.ROOT_TREE_OBJECTID), err)
}
rootItem, err := rootTree.TreeSearch(ctx, SearchRootItem(treeID))
if err != nil {
if errors.Is(err, ErrNoItem) {
err = fmt.Errorf("%w: %s", ErrNoTree, err)
}
return nil, fmt.Errorf("tree %s: %w", treeID.Format(btrfsprim.ROOT_TREE_OBJECTID), err)
}
switch rootItemBody := rootItem.Body.(type) {
case *btrfsitem.Root:
return &TreeRoot{
ID: treeID,
RootNode: rootItemBody.ByteNr,
Level: rootItemBody.Level,
Generation: rootItemBody.Generation,
RootInode: rootItemBody.RootDirID,
ParentUUID: rootItemBody.ParentUUID,
ParentGen: btrfsprim.Generation(rootItem.Key.Offset),
}, nil
case *btrfsitem.Error:
return nil, fmt.Errorf("malformed ROOT_ITEM for tree %v: %w", treeID, rootItemBody.Err)
default:
panic(fmt.Errorf("should not happen: ROOT_ITEM has unexpected item type: %T", rootItemBody))
}
}
}
// RawForrest //////////////////////////////////////////////////////////////////
// RawForrest implements Forrest.
type RawForrest struct {
NodeSource NodeSource
}
var _ Forrest = RawForrest{}
// RawTree is a variant of ForrestLookup that returns a concrete type
// instead of an interface.
func (forrest RawForrest) RawTree(ctx context.Context, treeID btrfsprim.ObjID) (*RawTree, error) {
sb, err := forrest.NodeSource.Superblock()
if err != nil {
return nil, err
}
rootInfo, err := LookupTreeRoot(ctx, forrest, *sb, treeID)
if err != nil {
return nil, err
}
return &RawTree{
Forrest: forrest,
TreeRoot: *rootInfo,
}, nil
}
// ForrestLookup implements Forrest.
func (forrest RawForrest) ForrestLookup(ctx context.Context, treeID btrfsprim.ObjID) (Tree, error) {
tree, err := forrest.RawTree(ctx, treeID)
if err != nil {
return nil, err
}
return tree, nil
}
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