1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
|
package btrfs
import (
"fmt"
"reflect"
"time"
"lukeshu.com/btrfs-tools/pkg/binstruct"
)
type (
PhysicalAddr int64
LogicalAddr int64
Generation uint64
)
type Key struct {
ObjectID ObjID `bin:"off=0, siz=8"` // Each tree has its own set of Object IDs.
ItemType ItemType `bin:"off=8, siz=1"`
Offset uint64 `bin:"off=9, siz=8"` // The meaning depends on the item type.
binstruct.End `bin:"off=11"`
}
type Time struct {
Sec int64 `bin:"off=0, siz=8"` // Number of seconds since 1970-01-01T00:00:00Z.
NSec uint64 `bin:"off=8, siz=4"` // Number of nanoseconds since the beginning of the second.
binstruct.End `bin:"off=c"`
}
func (t Time) ToStd() time.Time {
return time.Unix(t.Sec, int64(t.NSec))
}
type Superblock struct {
Checksum CSum `bin:"off=0, siz=20"` // Checksum of everything past this field (from 20 to 1000)
FSUUID UUID `bin:"off=20, siz=10"` // FS UUID
Self PhysicalAddr `bin:"off=30, siz=8"` // physical address of this block (different for mirrors)
Flags uint64 `bin:"off=38, siz=8"` // flags
Magic [8]byte `bin:"off=40, siz=8"` // magic ('_BHRfS_M')
Generation Generation `bin:"off=48, siz=8"`
RootTree LogicalAddr `bin:"off=50, siz=8"` // logical address of the root tree root
ChunkTree LogicalAddr `bin:"off=58, siz=8"` // logical address of the chunk tree root
LogTree LogicalAddr `bin:"off=60, siz=8"` // logical address of the log tree root
LogRootTransID uint64 `bin:"off=68, siz=8"` // log_root_transid
TotalBytes uint64 `bin:"off=70, siz=8"` // total_bytes
BytesUsed uint64 `bin:"off=78, siz=8"` // bytes_used
RootDirObjectID ObjID `bin:"off=80, siz=8"` // root_dir_objectid (usually 6)
NumDevices uint64 `bin:"off=88, siz=8"` // num_devices
SectorSize uint32 `bin:"off=90, siz=4"`
NodeSize uint32 `bin:"off=94, siz=4"`
LeafSize uint32 `bin:"off=98, siz=4"` // unused; must be the same as NodeSize
StripeSize uint32 `bin:"off=9c, siz=4"`
SysChunkArraySize uint32 `bin:"off=a0, siz=4"`
ChunkRootGeneration Generation `bin:"off=a4, siz=8"`
CompatFlags uint64 `bin:"off=ac, siz=8"` // compat_flags
CompatROFlags uint64 `bin:"off=b4, siz=8"` // compat_ro_flags - only implementations that support the flags can write to the filesystem
IncompatFlags IncompatFlags `bin:"off=bc, siz=8"` // incompat_flags - only implementations that support the flags can use the filesystem
ChecksumType uint16 `bin:"off=c4, siz=2"` // csum_type - Btrfs currently uses the CRC32c little-endian hash function with seed -1.
RootLevel uint8 `bin:"off=c6, siz=1"` // root_level
ChunkLevel uint8 `bin:"off=c7, siz=1"` // chunk_root_level
LogLevel uint8 `bin:"off=c8, siz=1"` // log_root_level
DevItem DevItem `bin:"off=c9, siz=62"` // DEV_ITEM data for this device
Label [0x100]byte `bin:"off=12b, siz=100"` // label (may not contain '/' or '\\')
CacheGeneration Generation `bin:"off=22b, siz=8"`
UUIDTreeGeneration uint64 `bin:"off=233, siz=8"` // uuid_tree_generation
// FeatureIncompatMetadataUUID
MetadataUUID UUID `bin:"off=23b, siz=10"`
// FeatureIncompatExtentTreeV2
NumGlobalRoots uint64 `bin:"off=24b, siz=8"`
// FeatureIncompatExtentTreeV2
BlockGroupRoot LogicalAddr `bin:"off=253, siz=8"`
BlockGroupRootGeneration Generation `bin:"off=25b, siz=8"`
BlockGroupRootLevel uint8 `bin:"off=263, siz=1"`
Reserved [199]byte `bin:"off=264, siz=c7"` // future expansion
SysChunkArray [0x800]byte `bin:"off=32b, siz=800"` // sys_chunk_array:(n bytes valid) Contains (KEY . CHUNK_ITEM) pairs for all SYSTEM chunks. This is needed to bootstrap the mapping from logical addresses to physical.
SuperRoots [4]RootBackup `bin:"off=b2b, siz=2a0"`
// Padded to 4096 bytes
Padding [565]byte `bin:"off=dcb, siz=235"`
binstruct.End `bin:"off=1000"`
}
func (sb Superblock) CalculateChecksum() (CSum, error) {
data, err := binstruct.Marshal(sb)
if err != nil {
return CSum{}, err
}
return CRC32c(data[0x20:]), nil
}
func (sb Superblock) ValidateChecksum() error {
stored := sb.Checksum
calced, err := sb.CalculateChecksum()
if err != nil {
return err
}
if !calced.Equal(stored) {
return fmt.Errorf("superblock checksum mismatch: stored=%s calculated=%s",
stored, calced)
}
return nil
}
func (a Superblock) Equal(b Superblock) bool {
a.Checksum = CSum{}
a.Self = 0
b.Checksum = CSum{}
b.Self = 0
return reflect.DeepEqual(a, b)
}
func (sb Superblock) EffectiveMetadataUUID() UUID {
if !sb.IncompatFlags.Has(FeatureIncompatMetadataUUID) {
return sb.FSUUID
}
return sb.MetadataUUID
}
type SysChunk struct {
Key `bin:"off=0, siz=11"`
Chunk `bin:"off=11, siz=30"`
binstruct.End `bin:"off=41"`
}
func (sb Superblock) ParseSysChunkArray() ([]SysChunk, error) {
dat := sb.SysChunkArray[:sb.SysChunkArraySize]
var ret []SysChunk
for len(dat) > 0 {
var pair SysChunk
if err := binstruct.Unmarshal(dat, &pair); err != nil {
return nil, err
}
dat = dat[0x41:]
for i := 0; i < int(pair.Chunk.NumStripes); i++ {
var stripe Stripe
if err := binstruct.Unmarshal(dat, &stripe); err != nil {
return nil, err
}
pair.Chunk.Stripes = append(pair.Chunk.Stripes, stripe)
dat = dat[0x20:]
}
ret = append(ret, pair)
}
return ret, nil
}
type RootBackup struct {
TreeRoot ObjID `bin:"off=0, siz=8"`
TreeRootGen Generation `bin:"off=8, siz=8"`
ChunkRoot ObjID `bin:"off=10, siz=8"`
ChunkRootGen Generation `bin:"off=18, siz=8"`
ExtentRoot ObjID `bin:"off=20, siz=8"`
ExtentRootGen Generation `bin:"off=28, siz=8"`
FSRoot ObjID `bin:"off=30, siz=8"`
FSRootGen Generation `bin:"off=38, siz=8"`
DevRoot ObjID `bin:"off=40, siz=8"`
DevRootGen Generation `bin:"off=48, siz=8"`
ChecksumRoot ObjID `bin:"off=50, siz=8"`
ChecksumRootGen Generation `bin:"off=58, siz=8"`
TotalBytes uint64 `bin:"off=60, siz=8"`
BytesUsed uint64 `bin:"off=68, siz=8"`
NumDevices uint64 `bin:"off=70, siz=8"`
Unused [8 * 4]byte `bin:"off=78, siz=20"`
TreeRootLevel uint8 `bin:"off=98, siz=1"`
ChunkRootLevel uint8 `bin:"off=99, siz=1"`
ExtentRootLevel uint8 `bin:"off=9a, siz=1"`
FSRootLevel uint8 `bin:"off=9b, siz=1"`
DevRootLevel uint8 `bin:"off=9c, siz=1"`
ChecksumRootLevel uint8 `bin:"off=9d, siz=1"`
Padding [10]byte `bin:"off=9e, siz=a"`
binstruct.End `bin:"off=a8"`
}
type Node interface {
GetNodeHeader() Ref[LogicalAddr, NodeHeader]
}
type NodeHeader struct {
Checksum CSum `bin:"off=0, siz=20"` // Checksum of everything after this field (from 20 to the end of the node)
MetadataUUID UUID `bin:"off=20, siz=10"` // FS UUID
Addr LogicalAddr `bin:"off=30, siz=8"` // Logical address of this node
Flags NodeFlags `bin:"off=38, siz=7"`
BackrefRev uint8 `bin:"off=3f, siz=1"`
ChunkTreeUUID UUID `bin:"off=40, siz=10"` // Chunk tree UUID
Generation Generation `bin:"off=50, siz=8"` // Generation
Owner ObjID `bin:"off=58, siz=8"` // The ID of the tree that contains this node
NumItems uint32 `bin:"off=60, siz=4"` // Number of items
Level uint8 `bin:"off=64, siz=1"` // Level (0 for leaf nodes)
binstruct.End `bin:"off=65"`
Size uint32 `bin:"-"` // superblock.NodeSize
MaxItems uint32 `bin:"-"` // Maximum possible value of NumItems
}
type InternalNode struct {
Header Ref[LogicalAddr, NodeHeader]
Body []Ref[LogicalAddr, KeyPointer]
}
func (in *InternalNode) GetNodeHeader() Ref[LogicalAddr, NodeHeader] {
return in.Header
}
type KeyPointer struct {
Key Key `bin:"off=0, siz=11"`
BlockNumber uint64 `bin:"off=11, siz=8"`
Generation Generation `bin:"off=19, siz=8"`
binstruct.End `bin:"off=21"`
}
type LeafNode struct {
Header Ref[LogicalAddr, NodeHeader]
Body []Ref[LogicalAddr, Item]
}
func (ln *LeafNode) GetNodeHeader() Ref[LogicalAddr, NodeHeader] {
return ln.Header
}
func (ln *LeafNode) FreeSpace() uint32 {
freeSpace := ln.Header.Data.Size
freeSpace -= 0x65
for _, item := range ln.Body {
freeSpace -= 0x19
freeSpace -= item.Data.DataSize
}
return freeSpace
}
type Item struct {
Key Key `bin:"off=0, siz=11"`
DataOffset uint32 `bin:"off=11, siz=4"` // relative to the end of the header (0x65)
DataSize uint32 `bin:"off=15, siz=4"`
binstruct.End `bin:"off=19"`
Data Ref[LogicalAddr, []byte] `bin:"-"`
}
type DevItem struct {
DeviceID ObjID `bin:"off=0, siz=8"` // device ID
NumBytes uint64 `bin:"off=8, siz=8"` // number of bytes
NumBytesUsed uint64 `bin:"off=10, siz=8"` // number of bytes used
IOOptimalAlign uint32 `bin:"off=18, siz=4"` // optimal I/O align
IOOptimalWidth uint32 `bin:"off=1c, siz=4"` // optimal I/O width
IOMinSize uint32 `bin:"off=20, siz=4"` // minimal I/O size (sector size)
Type uint64 `bin:"off=24, siz=8"` // type
Generation Generation `bin:"off=2c, siz=8"` // generation
StartOffset uint64 `bin:"off=34, siz=8"` // start offset
DevGroup uint32 `bin:"off=3c, siz=4"` // dev group
SeekSpeed uint8 `bin:"off=40, siz=1"` // seek speed
Bandwidth uint8 `bin:"off=41, siz=1"` // bandwidth
DevUUID UUID `bin:"off=42, siz=10"` // device UUID
FSUUID UUID `bin:"off=52, siz=10"` // FS UUID
binstruct.End `bin:"off=62"`
}
type Chunk struct {
// Maps logical address to physical.
Size uint64 `bin:"off=0, siz=8"` // size of chunk (bytes)
Owner ObjID `bin:"off=8, siz=8"` // root referencing this chunk (2)
StripeLen uint64 `bin:"off=10, siz=8"` // stripe length
Type uint64 `bin:"off=18, siz=8"` // type (same as flags for block group?)
IOOptimalAlign uint32 `bin:"off=20, siz=4"` // optimal io alignment
IOOptimalWidth uint32 `bin:"off=24, siz=4"` // optimal io width
IoMinSize uint32 `bin:"off=28, siz=4"` // minimal io size (sector size)
NumStripes uint16 `bin:"off=2c, siz=2"` // number of stripes
SubStripes uint16 `bin:"off=2e, siz=2"` // sub stripes
binstruct.End `bin:"off=30"`
Stripes []Stripe `bin:"-"`
}
type Stripe struct {
// Stripes follow (for each number of stripes):
DeviceID ObjID `bin:"off=0, siz=8"` // device ID
Offset uint64 `bin:"off=8, siz=8"` // offset
DeviceUUID UUID `bin:"off=10, siz=10"` // device UUID
binstruct.End `bin:"off=20"`
}
|
