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|
package btrfs
import (
"bytes"
"fmt"
"reflect"
)
type FS struct {
Devices []*Device
initErr error
uuid2dev map[UUID]*Device
chunks []SysChunk
}
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)
}
}
return nil
}
func (fs *FS) ReadLogicalFull(laddr LogicalAddr, dat []byte) error {
done := LogicalAddr(0)
for done < LogicalAddr(len(dat)) {
n, err := fs.readLogicalMaybeShort(laddr+done, dat[done:])
if err != nil {
return err
}
done += LogicalAddr(n)
}
return nil
}
func (fs *FS) readLogicalMaybeShort(laddr LogicalAddr, dat []byte) (int, error) {
if err := fs.init(); err != nil {
return 0, err
}
type physicalAddr struct {
Dev UUID
Addr PhysicalAddr
}
paddrs := make(map[physicalAddr]struct{})
for _, chunk := range fs.chunks {
if chunk.Offset <= uint64(laddr) && uint64(laddr) < chunk.Offset+uint64(chunk.Chunk.Size) {
offsetWithinChunk := uint64(laddr) - chunk.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, int64(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
}
|
