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// Copyright (C) 2022 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package btrfsutil
import (
"context"
"fmt"
iofs "io/fs"
"sync"
"github.com/datawire/dlib/dlog"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
"git.lukeshu.com/btrfs-progs-ng/lib/containers"
"git.lukeshu.com/btrfs-progs-ng/lib/diskio"
)
type indexItem struct {
Key btrfs.Key
Path btrfs.TreePath
}
type cachedIndex struct {
Index *containers.RBTree[btrfs.Key, indexItem]
Err error
}
type brokenTrees struct {
ctx context.Context
inner *btrfs.FS
// btrfs.ROOT_TREE_OBJECTID
rootTreeMu sync.Mutex
rootTreeIndex *cachedIndex
// for all other trees
treeMu sync.Mutex
treeIndexes map[btrfs.ObjID]cachedIndex
}
var _ btrfs.Trees = (*brokenTrees)(nil)
// NewBrokenTrees wraps a *btrfs.FS to support looking up information
// from broken trees.
//
// Of the btrfs.FS.Tree{Verb}Trees methods:
//
// - TreeWalk works on broken trees
// - TreeLookup relies on the tree being properly ordered (which a
// broken tree might not be).
// - TreeSearch relies on the tree being properly ordered (which a
// broken tree might not be).
// - TreeSearchAll relies on the tree being properly ordered (which a
// broken tree might not be), and a bad node may cause it to not
// return a truncated list of results.
//
// NewBrokenTrees attempts to remedy these deficiencies by using
// .TreeWalk to build an out-of-FS index of all of the items in the
// tree, and re-implements TreeLookup, TreeSearch, and TreeSearchAll
// using that index.
func NewBrokenTrees(ctx context.Context, inner *btrfs.FS) btrfs.Trees {
return &brokenTrees{
ctx: ctx,
inner: inner,
}
}
func (bt *brokenTrees) treeIndex(treeID btrfs.ObjID) (*containers.RBTree[btrfs.Key, indexItem], error) {
var treeRoot *btrfs.TreeRoot
var err error
if treeID == btrfs.ROOT_TREE_OBJECTID {
bt.rootTreeMu.Lock()
defer bt.rootTreeMu.Unlock()
if bt.rootTreeIndex != nil {
return bt.rootTreeIndex.Index, bt.rootTreeIndex.Err
}
treeRoot, err = btrfs.LookupTreeRoot(bt.inner, treeID)
} else {
bt.treeMu.Lock()
defer bt.treeMu.Unlock()
if bt.treeIndexes == nil {
bt.treeIndexes = make(map[btrfs.ObjID]cachedIndex)
}
if cacheEntry, exists := bt.treeIndexes[treeID]; exists {
return cacheEntry.Index, cacheEntry.Err
}
treeRoot, err = btrfs.LookupTreeRoot(bt, treeID)
}
var cacheEntry cachedIndex
if err != nil {
cacheEntry.Err = err
} else {
cacheEntry.Index = &containers.RBTree[btrfs.Key, indexItem]{
KeyFn: func(item indexItem) btrfs.Key {
return item.Key
},
}
dlog.Infof(bt.ctx, "indexing tree %v...", treeID)
bt.inner.RawTreeWalk(
bt.ctx,
*treeRoot,
func(err *btrfs.TreeError) {
dlog.Error(bt.ctx, err)
},
btrfs.TreeWalkHandler{
Item: func(path btrfs.TreePath, item btrfs.Item) error {
if cacheEntry.Index.Lookup(item.Key) != nil {
panic(fmt.Errorf("dup key=%v in tree=%v", item.Key, treeID))
}
cacheEntry.Index.Insert(indexItem{
Path: path.DeepCopy(),
Key: item.Key,
})
return nil
},
},
)
dlog.Infof(bt.ctx, "... done indexing tree %v", treeID)
}
if treeID == btrfs.ROOT_TREE_OBJECTID {
bt.rootTreeIndex = &cacheEntry
} else {
bt.treeIndexes[treeID] = cacheEntry
}
return cacheEntry.Index, cacheEntry.Err
}
func (bt *brokenTrees) TreeLookup(treeID btrfs.ObjID, key btrfs.Key) (btrfs.Item, error) {
item, err := bt.TreeSearch(treeID, key.Cmp)
if err != nil {
err = fmt.Errorf("item with key=%v: %w", key, err)
}
return item, err
}
func (bt *brokenTrees) TreeSearch(treeID btrfs.ObjID, fn func(btrfs.Key) int) (btrfs.Item, error) {
index, err := bt.treeIndex(treeID)
if err != nil {
return btrfs.Item{}, err
}
indexItem := index.Search(func(indexItem indexItem) int {
return fn(indexItem.Key)
})
if indexItem == nil {
return btrfs.Item{}, iofs.ErrNotExist
}
node, err := bt.inner.ReadNode(indexItem.Value.Path.Node(-2).NodeAddr)
if err != nil {
return btrfs.Item{}, err
}
item := node.Data.BodyLeaf[indexItem.Value.Path.Node(-1).ItemIdx]
return item, nil
}
func (bt *brokenTrees) TreeSearchAll(treeID btrfs.ObjID, fn func(btrfs.Key) int) ([]btrfs.Item, error) {
index, err := bt.treeIndex(treeID)
if err != nil {
return nil, err
}
indexItems := index.SearchRange(func(indexItem indexItem) int {
return fn(indexItem.Key)
})
if len(indexItems) == 0 {
return nil, iofs.ErrNotExist
}
ret := make([]btrfs.Item, len(indexItems))
var node *diskio.Ref[btrfsvol.LogicalAddr, btrfs.Node]
for i := range indexItems {
if node == nil || node.Addr != indexItems[i].Path.Node(-2).NodeAddr {
var err error
node, err = bt.inner.ReadNode(indexItems[i].Path.Node(-2).NodeAddr)
if err != nil {
return nil, err
}
}
ret[i] = node.Data.BodyLeaf[indexItems[i].Path.Node(-1).ItemIdx]
}
return ret, nil
}
func (bt *brokenTrees) TreeWalk(ctx context.Context, treeID btrfs.ObjID, errHandle func(*btrfs.TreeError), cbs btrfs.TreeWalkHandler) {
index, err := bt.treeIndex(treeID)
if err != nil {
errHandle(&btrfs.TreeError{
Path: btrfs.TreePath{
TreeID: treeID,
},
Err: err,
})
return
}
var node *diskio.Ref[btrfsvol.LogicalAddr, btrfs.Node]
_ = index.Walk(func(indexItem *containers.RBNode[indexItem]) error {
if ctx.Err() != nil {
return ctx.Err()
}
if bt.ctx.Err() != nil {
return bt.ctx.Err()
}
if cbs.Item != nil {
if node == nil || node.Addr != indexItem.Value.Path.Node(-2).NodeAddr {
var err error
node, err = bt.inner.ReadNode(indexItem.Value.Path.Node(-2).NodeAddr)
if err != nil {
errHandle(&btrfs.TreeError{Path: indexItem.Value.Path, Err: err})
return nil
}
}
item := node.Data.BodyLeaf[indexItem.Value.Path.Node(-1).ItemIdx]
if err := cbs.Item(indexItem.Value.Path, item); err != nil {
errHandle(&btrfs.TreeError{Path: indexItem.Value.Path, Err: err})
}
}
return nil
})
}
func (bt *brokenTrees) Superblock() (*btrfs.Superblock, error) {
return bt.inner.Superblock()
}
func (bt *brokenTrees) ReadAt(p []byte, off btrfsvol.LogicalAddr) (int, error) {
return bt.inner.ReadAt(p, off)
}
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