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package main
import (
"context"
"fmt"
"reflect"
"sync"
"github.com/datawire/dlib/dcontext"
"github.com/datawire/dlib/dlog"
lru "github.com/hashicorp/golang-lru"
"github.com/jacobsa/fuse"
"github.com/jacobsa/fuse/fuseutil"
"lukeshu.com/btrfs-tools/pkg/btrfs"
"lukeshu.com/btrfs-tools/pkg/btrfs/btrfsitem"
"lukeshu.com/btrfs-tools/pkg/btrfs/btrfsvol"
"lukeshu.com/btrfs-tools/pkg/util"
)
type Subvolume struct {
FS *btrfs.FS
DeviceName string
Mountpoint string
TreeID btrfs.ObjID
rootOnce sync.Once
rootVal btrfsitem.Root
rootErr error
inodeCache *lru.ARCCache
dirCache *lru.ARCCache
subvolumeFUSE
}
func (sv *Subvolume) Run(ctx context.Context) error {
mount, err := fuse.Mount(
sv.Mountpoint,
fuseutil.NewFileSystemServer(sv),
&fuse.MountConfig{
OpContext: ctx,
ErrorLogger: dlog.StdLogger(ctx, dlog.LogLevelError),
DebugLogger: dlog.StdLogger(ctx, dlog.LogLevelDebug),
FSName: sv.DeviceName,
Subtype: "btrfs",
ReadOnly: true,
})
if err != nil {
return err
}
return mount.Join(dcontext.HardContext(ctx))
}
func (sv *Subvolume) init() {
sv.rootOnce.Do(func() {
sb, err := sv.FS.Superblock()
if err != nil {
sv.rootErr = err
return
}
root, err := sv.FS.TreeLookup(sb.Data.RootTree, btrfs.Key{
ObjectID: sv.TreeID,
ItemType: btrfsitem.ROOT_ITEM_KEY,
Offset: 0,
})
if err != nil {
sv.rootErr = err
return
}
rootBody, ok := root.Body.(btrfsitem.Root)
if !ok {
sv.rootErr = fmt.Errorf("FS_TREE_ ROOT_ITEM has malformed body")
return
}
sv.rootVal = rootBody
sv.inodeCache, _ = lru.NewARC(128)
sv.dirCache, _ = lru.NewARC(128)
sv.subvolumeFUSE.init()
})
}
func (sv *Subvolume) getRootInode() (btrfs.ObjID, error) {
sv.init()
return sv.rootVal.RootDirID, sv.rootErr
}
func (sv *Subvolume) getFSTree() (btrfsvol.LogicalAddr, error) {
sv.init()
return sv.rootVal.ByteNr, sv.rootErr
}
func (sv *Subvolume) loadInode(inode btrfs.ObjID) (btrfsitem.Inode, error) {
tree, err := sv.getFSTree()
if err != nil {
return btrfsitem.Inode{}, nil
}
if ret, ok := sv.inodeCache.Get(inode); ok {
return ret.(btrfsitem.Inode), nil
}
item, err := sv.FS.TreeLookup(tree, btrfs.Key{
ObjectID: inode,
ItemType: btrfsitem.INODE_ITEM_KEY,
Offset: 0,
})
if err != nil {
return btrfsitem.Inode{}, err
}
itemBody, ok := item.Body.(btrfsitem.Inode)
if !ok {
return btrfsitem.Inode{}, fmt.Errorf("malformed inode")
}
sv.inodeCache.Add(inode, itemBody)
return itemBody, nil
}
type dir struct {
Inode btrfs.ObjID
InodeDat *btrfsitem.Inode
ChildrenByName map[string]btrfsitem.DirEntry
ChildrenByIndex map[uint64]btrfsitem.DirEntry
Errs []error
}
func (sv *Subvolume) loadDir(inode btrfs.ObjID) (*dir, error) {
tree, err := sv.getFSTree()
if err != nil {
return nil, err
}
if ret, ok := sv.dirCache.Get(inode); ok {
return ret.(*dir), nil
}
ret := &dir{
Inode: inode,
ChildrenByName: make(map[string]btrfsitem.DirEntry),
ChildrenByIndex: make(map[uint64]btrfsitem.DirEntry),
}
items, err := sv.FS.TreeSearchAll(tree, func(key btrfs.Key) int {
return util.CmpUint(inode, key.ObjectID)
})
if err != nil {
if len(items) == 0 {
return nil, err
}
ret.Errs = append(ret.Errs, err)
}
for _, item := range items {
switch item.Head.Key.ItemType {
case btrfsitem.INODE_ITEM_KEY:
itemBody := item.Body.(btrfsitem.Inode)
if ret.InodeDat != nil {
if !reflect.DeepEqual(itemBody, *ret.InodeDat) {
ret.Errs = append(ret.Errs, fmt.Errorf("multiple inodes"))
}
continue
}
ret.InodeDat = &itemBody
case btrfsitem.INODE_REF_KEY:
// TODO
case btrfsitem.DIR_ITEM_KEY:
body := item.Body.(btrfsitem.DirEntries)
if len(body) != 1 {
ret.Errs = append(ret.Errs, fmt.Errorf("multiple direntries in single DIR_ITEM?"))
continue
}
for _, entry := range body {
namehash := btrfsitem.NameHash(entry.Name)
if namehash != item.Head.Key.Offset {
ret.Errs = append(ret.Errs, fmt.Errorf("direntry crc32c mismatch: key=%#x crc32c(%q)=%#x",
item.Head.Key.Offset, entry.Name, namehash))
continue
}
if other, exists := ret.ChildrenByName[string(entry.Name)]; exists {
if !reflect.DeepEqual(entry, other) {
ret.Errs = append(ret.Errs, fmt.Errorf("multiple instances of direntry name %q", entry.Name))
}
continue
}
ret.ChildrenByName[string(entry.Name)] = entry
}
case btrfsitem.DIR_INDEX_KEY:
index := item.Head.Key.Offset
body := item.Body.(btrfsitem.DirEntries)
if len(body) != 1 {
ret.Errs = append(ret.Errs, fmt.Errorf("multiple direntries in single DIR_INDEX?"))
continue
}
for _, entry := range body {
if other, exists := ret.ChildrenByIndex[index]; exists {
if !reflect.DeepEqual(entry, other) {
ret.Errs = append(ret.Errs, fmt.Errorf("multiple instances of direntry index %v", index))
}
continue
}
ret.ChildrenByIndex[index] = entry
}
//case btrfsitem.XATTR_ITEM_KEY:
default:
ret.Errs = append(ret.Errs, fmt.Errorf("TODO: handle item type %v", item.Head.Key.ItemType))
}
}
entriesWithIndexes := make(map[string]struct{})
nextIndex := uint64(2)
for index, entry := range ret.ChildrenByIndex {
if index+1 > nextIndex {
nextIndex = index + 1
}
entriesWithIndexes[string(entry.Name)] = struct{}{}
if other, exists := ret.ChildrenByName[string(entry.Name)]; !exists {
ret.Errs = append(ret.Errs, fmt.Errorf("missing by-name direntry for %q", entry.Name))
ret.ChildrenByName[string(entry.Name)] = entry
} else if !reflect.DeepEqual(entry, other) {
ret.Errs = append(ret.Errs, fmt.Errorf("direntry index %v and direntry name %q disagree", index, entry.Name))
ret.ChildrenByName[string(entry.Name)] = entry
}
}
for _, name := range util.SortedMapKeys(ret.ChildrenByName) {
if _, exists := entriesWithIndexes[name]; !exists {
ret.Errs = append(ret.Errs, fmt.Errorf("missing by-index direntry for %q", name))
ret.ChildrenByIndex[nextIndex] = ret.ChildrenByName[name]
nextIndex++
}
}
sv.dirCache.Add(inode, ret)
return ret, nil
}
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