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// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
// Package btrfs (and its sub-packages) are the core implementation of
// the btrfs filesystem.
package btrfs
import (
"fmt"
"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfstree"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
"git.lukeshu.com/btrfs-progs-ng/lib/diskio"
)
type Device struct {
diskio.File[btrfsvol.PhysicalAddr]
cacheSuperblocks []*diskio.Ref[btrfsvol.PhysicalAddr, btrfstree.Superblock]
cacheSuperblock *btrfstree.Superblock
}
var _ diskio.File[btrfsvol.PhysicalAddr] = (*Device)(nil)
var SuperblockAddrs = []btrfsvol.PhysicalAddr{
0x00_0001_0000, // 64KiB
0x00_0400_0000, // 64MiB
0x40_0000_0000, // 256GiB
}
var SuperblockSize = btrfsvol.PhysicalAddr(binstruct.StaticSize(btrfstree.Superblock{}))
func (dev *Device) Superblocks() ([]*diskio.Ref[btrfsvol.PhysicalAddr, btrfstree.Superblock], error) {
if dev.cacheSuperblocks != nil {
return dev.cacheSuperblocks, nil
}
sz := dev.Size()
var ret []*diskio.Ref[btrfsvol.PhysicalAddr, btrfstree.Superblock]
for i, addr := range SuperblockAddrs {
if addr+SuperblockSize <= sz {
superblock := &diskio.Ref[btrfsvol.PhysicalAddr, btrfstree.Superblock]{
File: dev,
Addr: addr,
}
if err := superblock.Read(); err != nil {
return nil, fmt.Errorf("superblock %v: %w", i, err)
}
ret = append(ret, superblock)
}
}
if len(ret) == 0 {
return nil, fmt.Errorf("no superblocks")
}
dev.cacheSuperblocks = ret
return ret, nil
}
func (dev *Device) Superblock() (*btrfstree.Superblock, error) {
if dev.cacheSuperblock != nil {
return dev.cacheSuperblock, nil
}
sbs, err := dev.Superblocks()
if err != nil {
return nil, err
}
for i, sb := range sbs {
if err := sb.Data.ValidateChecksum(); err != nil {
return nil, fmt.Errorf("superblock %v: %w", i, err)
}
if i > 0 {
if !sb.Data.Equal(sbs[0].Data) {
return nil, fmt.Errorf("superblock %v and superblock %v disagree", 0, i)
}
}
}
dev.cacheSuperblock = &sbs[0].Data
return &sbs[0].Data, nil
}
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