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package btrfs
import (
"bytes"
"fmt"
"reflect"
"lukeshu.com/btrfs-tools/pkg/btrfs/btrfsitem"
"lukeshu.com/btrfs-tools/pkg/util"
)
type FS struct {
Devices []*Device
initErr error
uuid2dev map[UUID]*Device
chunks []SysChunk
}
func (fs *FS) Name() string {
sb, err := fs.Superblock()
if err != nil {
return fmt.Sprintf("fs_uuid=%s", "(unreadable)")
}
return fmt.Sprintf("fs_uuid=%s", sb.Data.FSUUID)
}
func (fs *FS) Size() (LogicalAddr, error) {
var ret LogicalAddr
for _, dev := range fs.Devices {
sz, err := dev.Size()
if err != nil {
return 0, fmt.Errorf("file %q: %w", dev.Name(), err)
}
ret += LogicalAddr(sz)
}
return ret, nil
}
func (fs *FS) Superblocks() ([]util.Ref[PhysicalAddr, Superblock], error) {
var ret []util.Ref[PhysicalAddr, Superblock]
for _, dev := range fs.Devices {
sbs, err := dev.Superblocks()
if err != nil {
return nil, fmt.Errorf("file %q: %w", dev.Name(), err)
}
ret = append(ret, sbs...)
}
return ret, nil
}
func (fs *FS) Superblock() (ret util.Ref[PhysicalAddr, Superblock], err error) {
sbs, err := fs.Superblocks()
if err != nil {
return ret, err
}
fname := ""
sbi := 0
for i, sb := range sbs {
if sb.File.Name() != fname {
fname = sb.File.Name()
sbi = 0
} else {
sbi++
}
if err := sb.Data.ValidateChecksum(); err != nil {
return ret, fmt.Errorf("file %q superblock %d: %w", sb.File.Name(), sbi, err)
}
if i > 0 {
// This is probably wrong, but lots of my
// multi-device code is probably wrong.
if !sb.Data.Equal(sbs[0].Data) {
return ret, fmt.Errorf("file %q superblock %d and file %q superblock %d disagree",
sbs[0].File.Name(), 0,
sb.File.Name(), sbi)
}
}
}
return sbs[0], nil
}
func (fs *FS) Init() error {
if fs.uuid2dev != nil {
return fs.initErr
}
fs.uuid2dev = make(map[UUID]*Device, len(fs.Devices))
for _, dev := range fs.Devices {
sbs, err := dev.Superblocks()
if err != nil {
fs.initErr = fmt.Errorf("file %q: %w", dev.Name(), err)
return fs.initErr
}
a := sbs[0].Data
a.Checksum = CSum{}
a.Self = 0
for i, sb := range sbs[1:] {
b := sb.Data
b.Checksum = CSum{}
b.Self = 0
if !reflect.DeepEqual(a, b) {
fs.initErr = fmt.Errorf("file %q: superblock %d disagrees with superblock 0",
dev.Name(), i+1)
return fs.initErr
}
}
sb := sbs[0]
if other, exists := fs.uuid2dev[sb.Data.DevItem.DevUUID]; exists {
fs.initErr = fmt.Errorf("file %q and file %q have the same device ID: %v",
other.Name(), dev.Name(), sb.Data.DevItem.DevUUID)
return fs.initErr
}
fs.uuid2dev[sb.Data.DevItem.DevUUID] = dev
syschunks, err := sb.Data.ParseSysChunkArray()
if err != nil {
fs.initErr = fmt.Errorf("file %q: %w", dev.Name(), err)
return fs.initErr
}
for _, chunk := range syschunks {
fs.chunks = append(fs.chunks, chunk)
}
if err := fs.WalkTree(sb.Data.ChunkTree, WalkTreeHandler{
Item: func(key Key, body btrfsitem.Item) error {
if key.ItemType != btrfsitem.CHUNK_ITEM_KEY {
return nil
}
fs.chunks = append(fs.chunks, SysChunk{
Key: key,
Chunk: body.(btrfsitem.Chunk),
})
return nil
},
}); err != nil {
fs.initErr = err
return fs.initErr
}
}
return nil
}
func (fs *FS) ReadAt(dat []byte, laddr LogicalAddr) (int, error) {
done := 0
for done < len(dat) {
n, err := fs.maybeShortReadAt(dat[done:], laddr+LogicalAddr(done))
done += n
if err != nil {
return done, err
}
}
return done, nil
}
func (fs *FS) maybeShortReadAt(dat []byte, laddr LogicalAddr) (int, error) {
type physicalAddr struct {
Dev UUID
Addr PhysicalAddr
}
paddrs := make(map[physicalAddr]struct{})
for _, chunk := range fs.chunks {
if chunk.Key.Offset <= uint64(laddr) && uint64(laddr) < chunk.Key.Offset+uint64(chunk.Chunk.Size) {
offsetWithinChunk := uint64(laddr) - chunk.Key.Offset
if offsetWithinChunk+uint64(len(dat)) > chunk.Chunk.Size {
dat = dat[:chunk.Chunk.Size-offsetWithinChunk]
}
for _, stripe := range chunk.Chunk.Stripes {
paddrs[physicalAddr{
Dev: stripe.DeviceUUID,
Addr: PhysicalAddr(stripe.Offset + offsetWithinChunk),
}] = struct{}{}
}
}
}
if len(paddrs) == 0 {
return 0, fmt.Errorf("could not map logical address %v", laddr)
}
buf := make([]byte, len(dat))
first := true
for paddr := range paddrs {
dev, ok := fs.uuid2dev[paddr.Dev]
if !ok {
return 0, fmt.Errorf("device=%s does not exist", paddr.Dev)
}
if _, err := dev.ReadAt(buf, paddr.Addr); err != nil {
return 0, fmt.Errorf("read device=%s paddr=%v: %w", paddr.Dev, paddr.Addr, err)
}
if first {
copy(dat, buf)
} else {
if !bytes.Equal(dat, buf) {
return 0, fmt.Errorf("inconsistent stripes at laddr=%v len=%d", laddr, len(dat))
}
}
}
return len(dat), nil
}
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