summaryrefslogtreecommitdiff
path: root/pkg/btrfs/io2_fs.go
blob: ff5415a0ac13d96a1297a70a02e445f8e2f3d540 (plain)
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
package btrfs

import (
	"bytes"
	"fmt"
	"math"
	"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

	cacheSuperblocks []*util.Ref[PhysicalAddr, Superblock]
	cacheSuperblock  *util.Ref[PhysicalAddr, Superblock]
}

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) {
	if fs.cacheSuperblocks != nil {
		return fs.cacheSuperblocks, nil
	}
	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...)
	}
	fs.cacheSuperblocks = ret
	return ret, nil
}

func (fs *FS) Superblock() (*util.Ref[PhysicalAddr, Superblock], error) {
	if fs.cacheSuperblock != nil {
		return fs.cacheSuperblock, nil
	}
	sbs, err := fs.Superblocks()
	if err != nil {
		return nil, 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 nil, 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 nil, fmt.Errorf("file %q superblock %d and file %q superblock %d disagree",
					sbs[0].File.Name(), 0,
					sb.File.Name(), sbi)
			}
		}
	}

	fs.cacheSuperblock = sbs[0]
	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
}

type QualifiedPhysicalAddr struct {
	Dev  UUID
	Addr PhysicalAddr
}

func (fs *FS) Resolve(laddr LogicalAddr) (paddrs map[QualifiedPhysicalAddr]struct{}, maxlen uint64) {
	paddrs = make(map[QualifiedPhysicalAddr]struct{})
	maxlen = math.MaxUint64

	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
			maxlen = util.Min(maxlen, chunk.Chunk.Size-offsetWithinChunk)
			for _, stripe := range chunk.Chunk.Stripes {
				paddrs[QualifiedPhysicalAddr{
					Dev:  stripe.DeviceUUID,
					Addr: PhysicalAddr(stripe.Offset + offsetWithinChunk),
				}] = struct{}{}
			}
		}
	}

	return paddrs, maxlen
}

func (fs *FS) maybeShortReadAt(dat []byte, laddr LogicalAddr) (int, error) {
	paddrs, maxlen := fs.Resolve(laddr)
	if len(paddrs) == 0 {
		return 0, fmt.Errorf("could not map logical address %v", laddr)
	}
	if uint64(len(dat)) > maxlen {
		dat = dat[:maxlen]
	}

	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
}