btrfsitem

package
v0.1.0 Latest Latest
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This package is not in the latest version of its module.

 Go to latest Published: Jul 11, 2023 License: Apache-2.0, GPL-2.0, GPL-3.0-or-later, + 1 more Imports: 12 Imported by: 0

Documentation

Overview

Package btrfsitem contains the definitions of all "items" that may be stored in a btrfs tree.

Index

Constants

View Source 
const (
	DEV_STAT_WRITE_ERRS = iota
	DEV_STAT_READ_ERRS
	DEV_STAT_FLUSH_ERRS
	DEV_STAT_CORRUPTION_ERRS
	DEV_STAT_GENERATION_ERRS
	DEV_STAT_VALUES_MAX
)
View Source 
const (
	QGroupLimitFlagMaxRfer = 1 << iota
	QGroupLimitFlagMaxExcl
	QGroupLimitFlagRsvRfer
	QGroupLimitFlagRsvExcl
	QGroupLimitFlagRferCmpr
	QGroupLimitFlagExclCmpr
)
View Source 
const (
	BLOCK_GROUP_ITEM_KEY     = btrfsprim.BLOCK_GROUP_ITEM_KEY
	CHUNK_ITEM_KEY           = btrfsprim.CHUNK_ITEM_KEY
	DEV_EXTENT_KEY           = btrfsprim.DEV_EXTENT_KEY
	DEV_ITEM_KEY             = btrfsprim.DEV_ITEM_KEY
	DIR_INDEX_KEY            = btrfsprim.DIR_INDEX_KEY
	DIR_ITEM_KEY             = btrfsprim.DIR_ITEM_KEY
	EXTENT_CSUM_KEY          = btrfsprim.EXTENT_CSUM_KEY
	EXTENT_DATA_KEY          = btrfsprim.EXTENT_DATA_KEY
	EXTENT_DATA_REF_KEY      = btrfsprim.EXTENT_DATA_REF_KEY
	EXTENT_ITEM_KEY          = btrfsprim.EXTENT_ITEM_KEY
	FREE_SPACE_BITMAP_KEY    = btrfsprim.FREE_SPACE_BITMAP_KEY
	FREE_SPACE_EXTENT_KEY    = btrfsprim.FREE_SPACE_EXTENT_KEY
	FREE_SPACE_INFO_KEY      = btrfsprim.FREE_SPACE_INFO_KEY
	INODE_ITEM_KEY           = btrfsprim.INODE_ITEM_KEY
	INODE_REF_KEY            = btrfsprim.INODE_REF_KEY
	METADATA_ITEM_KEY        = btrfsprim.METADATA_ITEM_KEY
	ORPHAN_ITEM_KEY          = btrfsprim.ORPHAN_ITEM_KEY
	PERSISTENT_ITEM_KEY      = btrfsprim.PERSISTENT_ITEM_KEY
	QGROUP_INFO_KEY          = btrfsprim.QGROUP_INFO_KEY
	QGROUP_LIMIT_KEY         = btrfsprim.QGROUP_LIMIT_KEY
	QGROUP_RELATION_KEY      = btrfsprim.QGROUP_RELATION_KEY
	QGROUP_STATUS_KEY        = btrfsprim.QGROUP_STATUS_KEY
	ROOT_BACKREF_KEY         = btrfsprim.ROOT_BACKREF_KEY
	ROOT_ITEM_KEY            = btrfsprim.ROOT_ITEM_KEY
	ROOT_REF_KEY             = btrfsprim.ROOT_REF_KEY
	SHARED_BLOCK_REF_KEY     = btrfsprim.SHARED_BLOCK_REF_KEY
	SHARED_DATA_REF_KEY      = btrfsprim.SHARED_DATA_REF_KEY
	TREE_BLOCK_REF_KEY       = btrfsprim.TREE_BLOCK_REF_KEY
	UNTYPED_KEY              = btrfsprim.UNTYPED_KEY
	UUID_RECEIVED_SUBVOL_KEY = btrfsprim.UUID_RECEIVED_SUBVOL_KEY
	UUID_SUBVOL_KEY          = btrfsprim.UUID_SUBVOL_KEY
	XATTR_ITEM_KEY           = btrfsprim.XATTR_ITEM_KEY
)
View Source 
const MaxNameLen = 255
View Source 
const QGroupStatusVersion uint64 = 1

Variables

This section is empty.

Functions

func KeyToUUID 

func KeyToUUID(key btrfsprim.Key) btrfsprim.UUID

func NameHash 

func NameHash(dat []byte) uint64

func UUIDToKey 

func UUIDToKey(uuid btrfsprim.UUID) btrfsprim.Key

Types

type BlockGroup 

type BlockGroup struct {
	Used          int64                    `bin:"off=0, siz=8"`
	ChunkObjectID btrfsprim.ObjID          `bin:"off=8, siz=8"` // always FIRST_CHUNK_TREE_OBJECTID
	Flags         btrfsvol.BlockGroupFlags `bin:"off=16, siz=8"`
	binstruct.End `bin:"off=24"`
}

A BlockGroup tracks allocation of the logical address space.

Compare with:

  • DevExtents, which track allocation of the physical address space.
  • Chunks, which map logical addresses to physical addresses.

The relationship between the three is 

DevExtent---[many:one]---Chunk---[one:one]---BlockGroup

Key: 

key.objectid = logical_addr
key.offset   = size of chunk

func (BlockGroup) Clone 

func (o BlockGroup) Clone() BlockGroup

Clone is a handy method.

func (*BlockGroup) CloneItem 

func (o *BlockGroup) CloneItem() Item

CloneItem implements Item.

func (*BlockGroup) Free 

func (o *BlockGroup) Free()

Free implements Item.

type Chunk 

type Chunk struct {
	Head    ChunkHeader
	Stripes []ChunkStripe
}

A Chunk maps logical addresses to physical addresses.

Compare with:

  • DevExtents, which track allocation of the physical address space.
  • BlockGroups, which track allocation of the logical address space.

The relationship between the three is 

DevExtent---[many:one]---Chunk---[one:one]---BlockGroup

Key: 

key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID
key.offset   = logical_addr

func (Chunk) Clone 

func (chunk Chunk) Clone() Chunk

func (*Chunk) CloneItem 

func (o *Chunk) CloneItem() Item

func (*Chunk) Free 

func (chunk *Chunk) Free()

func (Chunk) Mappings 

func (chunk Chunk) Mappings(key btrfsprim.Key) []btrfsvol.Mapping

func (Chunk) MarshalBinary 

func (chunk Chunk) MarshalBinary() ([]byte, error)

func (*Chunk) UnmarshalBinary 

func (chunk *Chunk) UnmarshalBinary(dat []byte) (int, error)

type ChunkHeader 

type ChunkHeader struct {
	Size           btrfsvol.AddrDelta       `bin:"off=0x0,  siz=0x8"`
	Owner          btrfsprim.ObjID          `bin:"off=0x8,  siz=0x8"` // root referencing this chunk (always EXTENT_TREE_OBJECTID=2)
	StripeLen      uint64                   `bin:"off=0x10, siz=0x8"` // ???
	Type           btrfsvol.BlockGroupFlags `bin:"off=0x18, siz=0x8"`
	IOOptimalAlign uint32                   `bin:"off=0x20, siz=0x4"`
	IOOptimalWidth uint32                   `bin:"off=0x24, siz=0x4"`
	IOMinSize      uint32                   `bin:"off=0x28, siz=0x4"` // sector size
	NumStripes     uint16                   `bin:"off=0x2c, siz=0x2"` // [ignored-when-writing]
	SubStripes     uint16                   `bin:"off=0x2e, siz=0x2"` // ???
	binstruct.End  `bin:"off=0x30"`
}

type ChunkStripe 

type ChunkStripe struct {
	DeviceID      btrfsvol.DeviceID     `bin:"off=0x0,  siz=0x8"`
	Offset        btrfsvol.PhysicalAddr `bin:"off=0x8,  siz=0x8"`
	DeviceUUID    btrfsprim.UUID        `bin:"off=0x10, siz=0x10"`
	binstruct.End `bin:"off=0x20"`
}

type CompressionType 

type CompressionType uint8
const (
	COMPRESS_NONE CompressionType = iota
	COMPRESS_ZLIB
	COMPRESS_LZO
	COMPRESS_ZSTD
)

func (CompressionType) String 

func (ct CompressionType) String() string

type Dev 

type Dev struct {
	DevID btrfsvol.DeviceID `bin:"off=0x0,    siz=0x8"`

	NumBytes     uint64 `bin:"off=0x8,    siz=0x8"`
	NumBytesUsed uint64 `bin:"off=0x10,   siz=0x8"`

	IOOptimalAlign uint32 `bin:"off=0x18,   siz=0x4"`
	IOOptimalWidth uint32 `bin:"off=0x1c,   siz=0x4"`
	IOMinSize      uint32 `bin:"off=0x20,   siz=0x4"` // sector size

	Type        uint64               `bin:"off=0x24,   siz=0x8"`
	Generation  btrfsprim.Generation `bin:"off=0x2c,   siz=0x8"`
	StartOffset uint64               `bin:"off=0x34,   siz=0x8"`
	DevGroup    uint32               `bin:"off=0x3c,   siz=0x4"`
	SeekSpeed   uint8                `bin:"off=0x40,   siz=0x1"`
	Bandwidth   uint8                `bin:"off=0x41,   siz=0x1"`

	DevUUID btrfsprim.UUID `bin:"off=0x42,   siz=0x10"`
	FSUUID  btrfsprim.UUID `bin:"off=0x52,   siz=0x10"`

	binstruct.End `bin:"off=0x62"`
}

A Dev describes a physical volume that is part of the filesystem.

Key: 

key.objectid = BTRFS_DEV_ITEMS_OBJECTID
key.offset   = device_id (starting at 1)

func (Dev) Clone 

func (o Dev) Clone() Dev

func (*Dev) CloneItem 

func (o *Dev) CloneItem() Item

func (*Dev) Free 

func (o *Dev) Free()

type DevExtent 

type DevExtent struct {
	ChunkTree     btrfsprim.ObjID      `bin:"off=0, siz=8"`  // always CHUNK_TREE_OBJECTID
	ChunkObjectID btrfsprim.ObjID      `bin:"off=8, siz=8"`  // which chunk within .ChunkTree owns this extent, always FIRST_CHUNK_TREE_OBJECTID
	ChunkOffset   btrfsvol.LogicalAddr `bin:"off=16, siz=8"` // offset of the CHUNK_ITEM that owns this extent, within the .ChunkObjectID
	Length        btrfsvol.AddrDelta   `bin:"off=24, siz=8"`
	ChunkTreeUUID btrfsprim.UUID       `bin:"off=32, siz=16"`
	binstruct.End `bin:"off=48"`
}

A DevExtent tracks allocation of the physical address space.

Compare with:

  • BlockGroups, which track allocation of the logical address space.
  • Chunks, which map logical addresses to physical addresses.

The relationship between the three is 

DevExtent---[many:one]---Chunk---[one:one]---BlockGroup

The device ID identifies which Dev item describes the physical volume that the DevExtent is on.

Key: 

key.objectid = device_id
key.offset   = physical_addr

func (DevExtent) Clone 

func (o DevExtent) Clone() DevExtent

func (*DevExtent) CloneItem 

func (o *DevExtent) CloneItem() Item

func (*DevExtent) Free 

func (o *DevExtent) Free()

func (DevExtent) Mapping 

func (devext DevExtent) Mapping(key btrfsprim.Key) btrfsvol.Mapping

type DevStats 

type DevStats struct {
	Values        [DEV_STAT_VALUES_MAX]int64 `bin:"off=0, siz=40"`
	binstruct.End `bin:"off=40"`
}

func (DevStats) Clone 

func (o DevStats) Clone() DevStats

func (*DevStats) CloneItem 

func (o *DevStats) CloneItem() Item

func (*DevStats) Free 

func (o *DevStats) Free()

type DirEntry 

type DirEntry struct {
	Location      btrfsprim.Key `bin:"off=0x0, siz=0x11"`
	TransID       int64         `bin:"off=0x11, siz=8"`
	DataLen       uint16        `bin:"off=0x19, siz=2"` // [ignored-when-writing]
	NameLen       uint16        `bin:"off=0x1b, siz=2"` // [ignored-when-writing]
	Type          FileType      `bin:"off=0x1d, siz=1"`
	binstruct.End `bin:"off=0x1e"`
	Data          []byte `bin:"-"` // xattr value (only for XATTR_ITEM)
	Name          []byte `bin:"-"`
}

A DirEntry is an member of a directory.

Key: 

key.objectid = inode of directory containing this entry
key.offset   = one of:
  - for DIR_ITEM and XATTR_ITEM = NameHash(name)
  - for DIR_INDEX               = index id in the directory (starting at 2, because of "." and "..")

func (DirEntry) Clone 

func (o DirEntry) Clone() DirEntry

func (*DirEntry) CloneItem 

func (o *DirEntry) CloneItem() Item

func (*DirEntry) Free 

func (o *DirEntry) Free()

func (DirEntry) MarshalBinary 

func (o DirEntry) MarshalBinary() ([]byte, error)

func (*DirEntry) UnmarshalBinary 

func (o *DirEntry) UnmarshalBinary(dat []byte) (int, error)

type Empty 

type Empty struct {
	binstruct.End `bin:"off=0"`
}

func (Empty) Clone 

func (o Empty) Clone() Empty

func (*Empty) CloneItem 

func (o *Empty) CloneItem() Item

func (*Empty) Free 

func (o *Empty) Free()

type Error 

type Error struct {
	Dat []byte
	Err error
}

func (Error) Clone 

func (o Error) Clone() Error

func (*Error) CloneItem 

func (o *Error) CloneItem() Item

func (*Error) Free 

func (o *Error) Free()

func (Error) MarshalBinary 

func (o Error) MarshalBinary() ([]byte, error)

func (*Error) UnmarshalBinary 

func (o *Error) UnmarshalBinary(dat []byte) (int, error)

type Extent 

type Extent struct {
	Head ExtentHeader
	Info TreeBlockInfo // only if .Head.Flags.Has(EXTENT_FLAG_TREE_BLOCK)
	Refs []ExtentInlineRef
}

Extent items map from regions in the logical address space to regions in a file.

Compare with:

  • Metadata, which are like Extents but without .Info.
  • FileExtents, which map from regions in a file to regions in the logical address space.

An Extent may contain (inline or not) several ExtentDataRef items and/or ShareDataRef items.

Key: 

key.objectid = laddr of the extent
key.offset   = length of the extent

func (Extent) Clone 

func (o Extent) Clone() Extent

func (*Extent) CloneItem 

func (o *Extent) CloneItem() Item

func (*Extent) Free 

func (o *Extent) Free()

func (Extent) MarshalBinary 

func (o Extent) MarshalBinary() ([]byte, error)

func (*Extent) UnmarshalBinary 

func (o *Extent) UnmarshalBinary(dat []byte) (int, error)

type ExtentCSum 

type ExtentCSum struct {
	// Checksum of each sector starting at key.offset
	btrfssum.SumRun[btrfsvol.LogicalAddr]
}

An ExtentCSum checksums regions of the logical address space.

Key: 

key.objectid = BTRFS_EXTENT_CSUM_OBJECTID
key.offset   = laddr of checksummed region

func (ExtentCSum) Clone 

func (o ExtentCSum) Clone() ExtentCSum

func (*ExtentCSum) CloneItem 

func (o *ExtentCSum) CloneItem() Item

func (*ExtentCSum) Free 

func (o *ExtentCSum) Free()

func (ExtentCSum) MarshalBinary 

func (o ExtentCSum) MarshalBinary() ([]byte, error)

func (*ExtentCSum) UnmarshalBinary 

func (o *ExtentCSum) UnmarshalBinary(dat []byte) (int, error)

type ExtentDataRef 

type ExtentDataRef struct {
	Root          btrfsprim.ObjID `bin:"off=0, siz=8"`  // subvolume tree ID that references this extent
	ObjectID      btrfsprim.ObjID `bin:"off=8, siz=8"`  // inode number that references this extent within the .Root subvolume
	Offset        int64           `bin:"off=16, siz=8"` // byte offset for the extent within the file
	Count         int32           `bin:"off=24, siz=4"` // reference count
	binstruct.End `bin:"off=28"`
}

ExtentDataRef is part of an Extent.

Key: 

key.objectid = laddr of the extent being referenced
key.offset   = crc32c([root,objectid,offset])

func (ExtentDataRef) Clone 

func (o ExtentDataRef) Clone() ExtentDataRef

func (*ExtentDataRef) CloneItem 

func (o *ExtentDataRef) CloneItem() Item

func (*ExtentDataRef) Free 

func (o *ExtentDataRef) Free()

type ExtentFlags 

type ExtentFlags uint64
const (
	EXTENT_FLAG_DATA ExtentFlags = 1 << iota
	EXTENT_FLAG_TREE_BLOCK
)

func (ExtentFlags) Has 

func (f ExtentFlags) Has(req ExtentFlags) bool

func (ExtentFlags) String 

func (f ExtentFlags) String() string

type ExtentHeader 

type ExtentHeader struct {
	Refs          int64                `bin:"off=0, siz=8"`
	Generation    btrfsprim.Generation `bin:"off=8, siz=8"`
	Flags         ExtentFlags          `bin:"off=16, siz=8"`
	binstruct.End `bin:"off=24"`
}

type ExtentInlineRef 

type ExtentInlineRef struct {
	Type   Type   // only 4 valid values: {TREE,SHARED}_BLOCK_REF_KEY, {EXTENT,SHARED}_DATA_REF_KEY
	Offset uint64 // only when Type != EXTENT_DATA_REF_KEY
	Body   Item   // only when Type == *_DATA_REF_KEY
}

func (ExtentInlineRef) MarshalBinary 

func (o ExtentInlineRef) MarshalBinary() ([]byte, error)

func (*ExtentInlineRef) UnmarshalBinary 

func (o *ExtentInlineRef) UnmarshalBinary(dat []byte) (int, error)

type FileExtent 

type FileExtent struct {
	Generation btrfsprim.Generation `bin:"off=0x0, siz=0x8"` // transaction ID that created this extent
	RAMBytes   int64                `bin:"off=0x8, siz=0x8"` // upper bound of what compressed data will decompress to

	// 32 bits describing the data encoding
	Compression   CompressionType `bin:"off=0x10, siz=0x1"`
	Encryption    uint8           `bin:"off=0x11, siz=0x1"`
	OtherEncoding uint16          `bin:"off=0x12, siz=0x2"` // reserved for later use

	Type FileExtentType `bin:"off=0x14, siz=0x1"` // inline data or real extent

	binstruct.End `bin:"off=0x15"`

	// only one of these, depending on .Type
	BodyInline []byte           `bin:"-"` // .Type == FILE_EXTENT_INLINE
	BodyExtent FileExtentExtent `bin:"-"` // .Type == FILE_EXTENT_REG or FILE_EXTENT_PREALLOC
}

FileExtent items map from regions in a file to regions in the logical address space.

Compare with:

  • Extents, which map from regions in the logical address space to regions in a file.
  • Metadata, which are like Extents but without .Info.

Key: 

key.objectid = inode
key.offset   = offset within file

func (FileExtent) Clone 

func (o FileExtent) Clone() FileExtent

func (*FileExtent) CloneItem 

func (o *FileExtent) CloneItem() Item

func (*FileExtent) Free 

func (o *FileExtent) Free()

func (FileExtent) MarshalBinary 

func (o FileExtent) MarshalBinary() ([]byte, error)

func (FileExtent) Size 

func (o FileExtent) Size() (int64, error)

func (*FileExtent) UnmarshalBinary 

func (o *FileExtent) UnmarshalBinary(dat []byte) (int, error)

type FileExtentExtent 

type FileExtentExtent struct {
	// Position and size of extent within the device
	DiskByteNr   btrfsvol.LogicalAddr `bin:"off=0x0, siz=0x8"`
	DiskNumBytes btrfsvol.AddrDelta   `bin:"off=0x8, siz=0x8"`

	// Position of data within the extent
	Offset btrfsvol.AddrDelta `bin:"off=0x10, siz=0x8"`

	// Decompressed/unencrypted size
	NumBytes int64 `bin:"off=0x18, siz=0x8"`

	binstruct.End `bin:"off=0x20"`
}

type FileExtentType 

type FileExtentType uint8
const (
	FILE_EXTENT_INLINE FileExtentType = iota
	FILE_EXTENT_REG
	FILE_EXTENT_PREALLOC
)

func (FileExtentType) String 

func (fet FileExtentType) String() string

type FileType 

type FileType uint8
const (
	FT_UNKNOWN FileType = iota
	FT_REG_FILE
	FT_DIR
	FT_CHRDEV
	FT_BLKDEV
	FT_FIFO
	FT_SOCK
	FT_SYMLINK
	FT_XATTR

	FT_MAX
)

func (FileType) String 

func (ft FileType) String() string

type FreeSpaceBitmap 

type FreeSpaceBitmap struct {
	Bitmap []byte
}

FreeSpaceBitmap is used in conjunction with FreeSpaceInfo for highly-fragmented blockgroups.

Key: 

key.objectid = object ID of the FreeSpaceInfo (logical_addr)
key.offset   = offset of the FreeSpaceInfo (size)

func (FreeSpaceBitmap) Clone 

func (o FreeSpaceBitmap) Clone() FreeSpaceBitmap

func (*FreeSpaceBitmap) CloneItem 

func (o *FreeSpaceBitmap) CloneItem() Item

func (*FreeSpaceBitmap) Free 

func (o *FreeSpaceBitmap) Free()

func (FreeSpaceBitmap) MarshalBinary 

func (o FreeSpaceBitmap) MarshalBinary() ([]byte, error)

func (*FreeSpaceBitmap) UnmarshalBinary 

func (o *FreeSpaceBitmap) UnmarshalBinary(dat []byte) (int, error)

type FreeSpaceFlags 

type FreeSpaceFlags uint32
const (
	FREE_SPACE_USING_BITMAPS FreeSpaceFlags = 1 << iota
)

func (FreeSpaceFlags) Has 

func (f FreeSpaceFlags) Has(req FreeSpaceFlags) bool

func (FreeSpaceFlags) String 

func (f FreeSpaceFlags) String() string

type FreeSpaceHeader 

type FreeSpaceHeader struct {
	Location      btrfsprim.Key        `bin:"off=0x00, siz=0x11"`
	Generation    btrfsprim.Generation `bin:"off=0x11, siz=0x8"`
	NumEntries    int64                `bin:"off=0x19, siz=0x8"`
	NumBitmaps    int64                `bin:"off=0x21, siz=0x8"`
	binstruct.End `bin:"off=0x29"`
}

func (FreeSpaceHeader) Clone 

func (o FreeSpaceHeader) Clone() FreeSpaceHeader

func (*FreeSpaceHeader) CloneItem 

func (o *FreeSpaceHeader) CloneItem() Item

func (*FreeSpaceHeader) Free 

func (o *FreeSpaceHeader) Free()

type FreeSpaceInfo 

type FreeSpaceInfo struct {
	ExtentCount   int32          `bin:"off=0, siz=4"`
	Flags         FreeSpaceFlags `bin:"off=4, siz=4"`
	binstruct.End `bin:"off=8"`
}

FreeSpaceInfo is the main way (v2) that free space is tracked in a BlockGroup. For highly-fragmented blockgorups, it may be augmented by a FreeSpaceBitmap.

Key: 

key.objectid = object ID of the BlockGroup (logical_addr)
key.offset   = offset of the BlockGroup (size)

func (FreeSpaceInfo) Clone 

func (o FreeSpaceInfo) Clone() FreeSpaceInfo

func (*FreeSpaceInfo) CloneItem 

func (o *FreeSpaceInfo) CloneItem() Item

func (*FreeSpaceInfo) Free 

func (o *FreeSpaceInfo) Free()

type Inode 

type Inode struct {
	Generation    btrfsprim.Generation `bin:"off=0x00, siz=0x08"`
	TransID       int64                `bin:"off=0x08, siz=0x08"`
	Size          int64                `bin:"off=0x10, siz=0x08"` // stat
	NumBytes      int64                `bin:"off=0x18, siz=0x08"` // allocated bytes, may be larger than size (or smaller if there are holes?)
	BlockGroup    btrfsprim.ObjID      `bin:"off=0x20, siz=0x08"` // only used for freespace inodes
	NLink         int32                `bin:"off=0x28, siz=0x04"` // stat
	UID           int32                `bin:"off=0x2C, siz=0x04"` // stat
	GID           int32                `bin:"off=0x30, siz=0x04"` // stat
	Mode          StatMode             `bin:"off=0x34, siz=0x04"` // stat
	RDev          int64                `bin:"off=0x38, siz=0x08"` // stat
	Flags         InodeFlags           `bin:"off=0x40, siz=0x08"` // statx.stx_attributes, sorta
	Sequence      int64                `bin:"off=0x48, siz=0x08"` // NFS
	Reserved      [4]int64             `bin:"off=0x50, siz=0x20"`
	ATime         btrfsprim.Time       `bin:"off=0x70, siz=0x0c"` // stat
	CTime         btrfsprim.Time       `bin:"off=0x7c, siz=0x0c"` // stat
	MTime         btrfsprim.Time       `bin:"off=0x88, siz=0x0c"` // stat
	OTime         btrfsprim.Time       `bin:"off=0x94, siz=0x0c"` // statx.stx_btime (why is this called "otime" instead of "btime"?)
	binstruct.End `bin:"off=0xa0"`
}

Inode is a file/dir/whatever in the filesystem. 

key.objectid = inode number
key.offset   = 0

func (Inode) Clone 

func (o Inode) Clone() Inode

func (*Inode) CloneItem 

func (o *Inode) CloneItem() Item

func (*Inode) Free 

func (o *Inode) Free()

type InodeFlags 

type InodeFlags uint64
const (
	INODE_NODATASUM InodeFlags = 1 << iota
	INODE_NODATACOW
	INODE_READONLY
	INODE_NOCOMPRESS
	INODE_PREALLOC
	INODE_SYNC
	INODE_IMMUTABLE
	INODE_APPEND
	INODE_NODUMP
	INODE_NOATIME
	INODE_DIRSYNC
	INODE_COMPRESS
)

func (InodeFlags) Has 

func (f InodeFlags) Has(req InodeFlags) bool

func (InodeFlags) String 

func (f InodeFlags) String() string

type InodeRef 

type InodeRef struct {
	Index         int64  `bin:"off=0x0, siz=0x8"`
	NameLen       uint16 `bin:"off=0x8, siz=0x2"` // [ignored-when-writing]
	binstruct.End `bin:"off=0xa"`
	Name          []byte `bin:"-"`
}

func (InodeRef) MarshalBinary 

func (o InodeRef) MarshalBinary() ([]byte, error)

func (*InodeRef) UnmarshalBinary 

func (o *InodeRef) UnmarshalBinary(dat []byte) (int, error)

type InodeRefs 

type InodeRefs struct {
	Refs []InodeRef
}

An InodeRefs item is a set of back-references that point to a given Inode.

Key: 

key.objectid = inode number of the file
key.offset   = inode number of the parent directory

There might be multiple back-references in a single InodeRef item if the same file has multiple hardlinks in the same directory.

func (InodeRefs) Clone 

func (o InodeRefs) Clone() InodeRefs

func (*InodeRefs) CloneItem 

func (o *InodeRefs) CloneItem() Item

func (*InodeRefs) Free 

func (o *InodeRefs) Free()

func (InodeRefs) MarshalBinary 

func (o InodeRefs) MarshalBinary() ([]byte, error)

func (*InodeRefs) UnmarshalBinary 

func (o *InodeRefs) UnmarshalBinary(dat []byte) (int, error)

type Item 

type Item interface {
	Free()
	CloneItem() Item
	// contains filtered or unexported methods
}

func UnmarshalItem 

func UnmarshalItem(key btrfsprim.Key, csumType btrfssum.CSumType, dat []byte) Item

UnmarshalItem consumes the byte slice `dat`, unmarshaling it in to the item type specified by `key`.

If there is an error, rather than returning a separate error value, return an Error item.

type Metadata 

type Metadata struct {
	Head ExtentHeader
	Refs []ExtentInlineRef
}

Metadata items map from regions in the logical address space to regions in a file.

Metadata is like Extent, but doesn't have .Info.

Compare with:

  • Extents, which are the same as Metadata, but have an extra .Info member.
  • FileExtents, which map from regions in a file to regions in the logical address space.

Key: 

key.objectid = laddr of the extent
key.offset   = length of the extent

func (Metadata) Clone 

func (o Metadata) Clone() Metadata

func (*Metadata) CloneItem 

func (o *Metadata) CloneItem() Item

func (*Metadata) Free 

func (o *Metadata) Free()

func (Metadata) MarshalBinary 

func (o Metadata) MarshalBinary() ([]byte, error)

func (*Metadata) UnmarshalBinary 

func (o *Metadata) UnmarshalBinary(dat []byte) (int, error)

type QGroupInfo 

type QGroupInfo struct {
	Generation                btrfsprim.Generation `bin:"off=0, siz=8"`
	ReferencedBytes           uint64               `bin:"off=8, siz=8"`
	ReferencedBytesCompressed uint64               `bin:"off=16, siz=8"`
	ExclusiveBytes            uint64               `bin:"off=24, siz=8"`
	ExclusiveBytesCompressed  uint64               `bin:"off=32, siz=8"`
	binstruct.End             `bin:"off=40"`
}

QGroupInfo tracks the amount of space used by a given qgroup in the containing subvolume.

Key: 

key.objectid = 0
key.offset   = ID of the qgroup

func (QGroupInfo) Clone 

func (o QGroupInfo) Clone() QGroupInfo

func (*QGroupInfo) CloneItem 

func (o *QGroupInfo) CloneItem() Item

func (*QGroupInfo) Free 

func (o *QGroupInfo) Free()

type QGroupLimit 

type QGroupLimit struct {
	Flags         QGroupLimitFlags `bin:"off=0, siz=8"`
	MaxReferenced uint64           `bin:"off=8, siz=8"`
	MaxExclusive  uint64           `bin:"off=16, siz=8"`
	RsvReferenced uint64           `bin:"off=24, siz=8"`
	RsvExclusive  uint64           `bin:"off=32, siz=8"`
	binstruct.End `bin:"off=40"`
}

QGroupLimit configures the maximum permissible amount of space that a given qgroup can consume (tracked in a QGroupInfo item) on the containing subvolume.

Key: 

key.objectid = 0
key.offset   = ID of the qgroup

func (QGroupLimit) Clone 

func (o QGroupLimit) Clone() QGroupLimit

func (*QGroupLimit) CloneItem 

func (o *QGroupLimit) CloneItem() Item

func (*QGroupLimit) Free 

func (o *QGroupLimit) Free()

type QGroupLimitFlags 

type QGroupLimitFlags uint64

func (QGroupLimitFlags) Has 

func (f QGroupLimitFlags) Has(req QGroupLimitFlags) bool

func (QGroupLimitFlags) String 

func (f QGroupLimitFlags) String() string

type QGroupStatus 

type QGroupStatus struct {
	Version        uint64               `bin:"off=0, siz=8"`
	Generation     btrfsprim.Generation `bin:"off=8, siz=8"`
	Flags          QGroupStatusFlags    `bin:"off=16, siz=8"`
	RescanProgress btrfsvol.LogicalAddr `bin:"off=24, siz=8"`
	binstruct.End  `bin:"off=32"`
}

A QGroupStatus holds the qgroup state of a subvolume (I think that implies that the QGroupStatus goes in the subvolume tree that it is describing?).

Key: 

key.objectid = 0
key.offset   = 0

func (QGroupStatus) Clone 

func (o QGroupStatus) Clone() QGroupStatus

func (*QGroupStatus) CloneItem 

func (o *QGroupStatus) CloneItem() Item

func (*QGroupStatus) Free 

func (o *QGroupStatus) Free()

type QGroupStatusFlags 

type QGroupStatusFlags uint64
const (
	QGroupStatusFlagOn QGroupStatusFlags = 1 << iota
	QGroupStatusFlagRescan
	QGroupStatusFlagInconsistent
)

func (QGroupStatusFlags) Has 

func (f QGroupStatusFlags) Has(req QGroupStatusFlags) bool

func (QGroupStatusFlags) String 

func (f QGroupStatusFlags) String() string

type Root 

type Root struct {
	Inode         Inode                `bin:"off=0x000, siz=0xa0"` // ???
	Generation    btrfsprim.Generation `bin:"off=0x0a0, siz=0x08"`
	RootDirID     btrfsprim.ObjID      `bin:"off=0x0a8, siz=0x08"` // inode number of the root inode
	ByteNr        btrfsvol.LogicalAddr `bin:"off=0x0b0, siz=0x08"` // root node
	ByteLimit     int64                `bin:"off=0x0b8, siz=0x08"` // always 0 (unused)
	BytesUsed     int64                `bin:"off=0x0c0, siz=0x08"`
	LastSnapshot  int64                `bin:"off=0x0c8, siz=0x08"`
	Flags         RootFlags            `bin:"off=0x0d0, siz=0x08"`
	Refs          int32                `bin:"off=0x0d8, siz=0x04"`
	DropProgress  btrfsprim.Key        `bin:"off=0x0dc, siz=0x11"`
	DropLevel     uint8                `bin:"off=0x0ed, siz=0x01"`
	Level         uint8                `bin:"off=0x0ee, siz=0x01"`
	GenerationV2  btrfsprim.Generation `bin:"off=0x0ef, siz=0x08"`
	UUID          btrfsprim.UUID       `bin:"off=0x0f7, siz=0x10"`
	ParentUUID    btrfsprim.UUID       `bin:"off=0x107, siz=0x10"`
	ReceivedUUID  btrfsprim.UUID       `bin:"off=0x117, siz=0x10"`
	CTransID      int64                `bin:"off=0x127, siz=0x08"`
	OTransID      int64                `bin:"off=0x12f, siz=0x08"`
	STransID      int64                `bin:"off=0x137, siz=0x08"`
	RTransID      int64                `bin:"off=0x13f, siz=0x08"`
	CTime         btrfsprim.Time       `bin:"off=0x147, siz=0x0c"`
	OTime         btrfsprim.Time       `bin:"off=0x153, siz=0x0c"`
	STime         btrfsprim.Time       `bin:"off=0x15f, siz=0x0c"`
	RTime         btrfsprim.Time       `bin:"off=0x16b, siz=0x0c"`
	GlobalTreeID  btrfsprim.ObjID      `bin:"off=0x177, siz=0x08"` // ???
	Reserved      [7]int64             `bin:"off=0x17f, siz=0x38"`
	binstruct.End `bin:"off=0x1b7"`
}

A Root goes in the ROOT_TREE and defines one of the other trees in the filesystem. All trees have a Root item describing them, except for the ROOT_TREE, CHUNK_TREE, TREE_LOG, and BLOCK_GROUP_TREE, which are defined directly in the superblock.

Key: 

key.objectid = tree ID
key.offset   = one of:
   - 0 if objectid is one of the BTRFS_*_TREE_OBJECTID defines or a non-snapshot volume; or
   - transaction_id of when this snapshot was created

This tree might contain nodes with node.Head.Owner set to the root.ParentUUID tree, *if* the node.Head.Generation is less-than-or-equal-to the root's key.offset. The "or-equal-to" part of that might be surprising, which is why I called it out.

func (Root) Clone 

func (o Root) Clone() Root

func (*Root) CloneItem 

func (o *Root) CloneItem() Item

func (*Root) Free 

func (o *Root) Free()

type RootFlags 

type RootFlags uint64
const (
	ROOT_SUBVOL_RDONLY RootFlags = 1 << iota
)

func (RootFlags) Has 

func (f RootFlags) Has(req RootFlags) bool

func (RootFlags) String 

func (f RootFlags) String() string

type RootRef 

type RootRef struct {
	DirID         btrfsprim.ObjID `bin:"off=0x00, siz=0x8"` // inode of the parent directory of the dir entry
	Sequence      int64           `bin:"off=0x08, siz=0x8"` // index of that dir entry within the parent
	NameLen       uint16          `bin:"off=0x10, siz=0x2"` // [ignored-when-writing]
	binstruct.End `bin:"off=0x12"`
	Name          []byte `bin:"-"`
}

A RootRef links subvolumes parent→child for normal subvolumes and base→snapshot for snapshot subvolumes. BACKREF items go the other direction; child→parent and snapshot→base.

Key: 

               ROOT_REF                   | ROOT_BACKREF
key.objectid = ID of the parent subvolume | ID of the child subvolume
key.offset   = ID of the child subvolume  | ID of the parent subvolume

func (RootRef) Clone 

func (o RootRef) Clone() RootRef

func (*RootRef) CloneItem 

func (o *RootRef) CloneItem() Item

func (*RootRef) Free 

func (o *RootRef) Free()

func (RootRef) MarshalBinary 

func (o RootRef) MarshalBinary() ([]byte, error)

func (*RootRef) UnmarshalBinary 

func (o *RootRef) UnmarshalBinary(dat []byte) (int, error)

type SharedDataRef 

type SharedDataRef struct {
	Count         int32 `bin:"off=0, siz=4"` // reference count
	binstruct.End `bin:"off=4"`
}

SharedDataRef is part of an Extent.

Key: 

key.objectid = laddr of the extent being referenced
key.offset   = laddr of the leaf node containing the FileExtent (EXTENT_DATA_KEY) for this reference.

func (SharedDataRef) Clone 

func (o SharedDataRef) Clone() SharedDataRef

func (*SharedDataRef) CloneItem 

func (o *SharedDataRef) CloneItem() Item

func (*SharedDataRef) Free 

func (o *SharedDataRef) Free()

type StatMode 

type StatMode uint32
const (
	ModeFmt StatMode = 0o17_0000 // mask for the type bits

	ModeFmtNamedPipe  StatMode = 0o01_0000 // type: named pipe (FIFO)
	ModeFmtCharDevice StatMode = 0o02_0000 // type: character device

	ModeFmtDir StatMode = 0o04_0000 // type: directory

	ModeFmtBlockDevice StatMode = 0o06_0000 // type: block device

	ModeFmtRegular StatMode = 0o10_0000 // type: regular file

	ModeFmtSymlink StatMode = 0o12_0000 // type: symbolic link

	ModeFmtSocket StatMode = 0o14_0000 // type: socket file

	ModePerm StatMode = 0o00_7777 // mask for permission bits

	ModePermSetUID StatMode = 0o00_4000 // permission: set user id
	ModePermSetGID StatMode = 0o00_2000 // permission: set group ID
	ModePermSticky StatMode = 0o00_1000 // permission: sticky bit

	ModePermUsrR StatMode = 0o00_0400 // permission: user: read
	ModePermUsrW StatMode = 0o00_0200 // permission: user: write
	ModePermUsrX StatMode = 0o00_0100 // permission: user: execute

	ModePermGrpR StatMode = 0o00_0040 // permission: group: read
	ModePermGrpW StatMode = 0o00_0020 // permission: group: write
	ModePermGrpX StatMode = 0o00_0010 // permission: group: execute

	ModePermOthR StatMode = 0o00_0004 // permission: other: read
	ModePermOthW StatMode = 0o00_0002 // permission: other: write
	ModePermOthX StatMode = 0o00_0001 // permission: other: execute
)

func (StatMode) IsDir 

func (mode StatMode) IsDir() bool

IsDir reports whether mode describes a directory.

That is, it tests that the ModeFmt bits are set to ModeFmtDir.

func (StatMode) IsRegular 

func (mode StatMode) IsRegular() bool

IsRegular reports whether m describes a regular file.

That is, it tests that the ModeFmt bits are set to ModeFmtRegular.

func (StatMode) String 

func (mode StatMode) String() string

String returns a textual representation of the mode.

This is the format that POSIX specifies for showing the mode in the output of the `ls -l` command. POSIX does not specify the character to use to indicate a ModeFmtSocket file; this method uses 's' (GNU `ls` behavior; though POSIX notes that many implementations use '=' for sockets).

type TreeBlockInfo 

type TreeBlockInfo struct {
	Key           btrfsprim.Key `bin:"off=0, siz=0x11"`
	Level         uint8         `bin:"off=0x11, siz=0x1"`
	binstruct.End `bin:"off=0x12"`
}

type Type 

type Type = btrfsprim.ItemType

type UUIDMap 

type UUIDMap struct {
	ObjID         btrfsprim.ObjID `bin:"off=0, siz=8"`
	binstruct.End `bin:"off=8"`
}

A UUIDMap item goes in the UUID_TREE and maps from a UUID to a btrfsprim.ObjID.

The Key for this item is a UUID, and the item is a subvolume ID that UUID maps to.

Key: 

key.objectid = first half of UUID
key.offset   = second half of UUID

func (UUIDMap) Clone 

func (o UUIDMap) Clone() UUIDMap

func (*UUIDMap) CloneItem 

func (o *UUIDMap) CloneItem() Item

func (*UUIDMap) Free 

func (o *UUIDMap) Free()

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