Enum ObjectId 

pub enum ObjectId {
    RootTree,
    ExtentTree,
    ChunkTree,
    DevTree,
    FsTree,
    RootTreeDir,
    CsumTree,
    QuotaTree,
    UuidTree,
    FreeSpaceTree,
    BlockGroupTree,
    RaidStripeTree,
    RemapTree,
    DeviceStats,
    Balance,
    Orphan,
    TreeLog,
    TreeLogFixup,
    TreeReloc,
    DataRelocTree,
    ExtentCsum,
    FreeSpace,
    FreeIno,
    CsumChange,
    Multiple,
    FirstFree,
    Id(u64),
}

Well-known btrfs object IDs used as tree IDs, namespace roots, and special-purpose objectids in item keys.

Variants

RootTree

The root tree (objectid 1). Contains ROOT_ITEM entries pointing to the root block of every other tree in the filesystem.

ExtentTree

The extent tree (objectid 2). Tracks all allocated extents (metadata tree blocks and data extents) with backreferences to their owners.

ChunkTree

The chunk tree (objectid 3). Maps logical address ranges to physical device stripes. Bootstrapped from the superblock’s sys_chunk_array.

DevTree

The device tree (objectid 4). Contains per-device extent allocation records (DEV_EXTENT items).

FsTree

The default FS tree (objectid 5). Holds the filesystem content (inodes, directory entries, file extents) for the top-level subvolume. Additional subvolumes/snapshots have objectids >= 256.

RootTreeDir

The root tree directory (objectid 6). A virtual directory entry in the root tree that links to the default subvolume.

CsumTree

The checksum tree (objectid 7). Stores per-block data checksums as EXTENT_CSUM items.

QuotaTree

The quota tree (objectid 8). Contains qgroup status, info, limit, and relation items for space accounting.

UuidTree

The UUID tree (objectid 9). Provides fast UUID-to-subvolume lookups for send/receive operations.

FreeSpaceTree

The free space tree (objectid 10). Tracks free space per block group using extent or bitmap items, replacing the older free space cache (v1).

BlockGroupTree

The block group tree (objectid 11). Separates block group items from the extent tree for faster mount times (requires the block_group_tree compat-ro feature).

RaidStripeTree

The RAID stripe tree (objectid 12). Maps logical extents to per-device physical stripe offsets for the raid-stripe-tree feature.

RemapTree

The remap tree (objectid 13). Reserved for future use by the extent-tree-v2 feature.

DeviceStats

Device statistics objectid (0). Used with PERSISTENT_ITEM_KEY to store per-device I/O error counters.

Balance

Balance status objectid (-4 as u64). Stored in the root tree as a TEMPORARY_ITEM to persist in-progress balance state.

Orphan

Orphan objectid (-5 as u64). Used as the objectid for ORPHAN_ITEM keys that mark inodes pending cleanup.

TreeLog

Tree log objectid (-6 as u64). The tree log records recent fsync’d changes for fast replay after a crash.

TreeLogFixup

Tree log fixup objectid (-7 as u64). Temporary items created during log replay to resolve backreferences.

TreeReloc

Tree relocation objectid (-8 as u64). Used during balance to hold relocated tree blocks before they are committed to their final location.

DataRelocTree

Data relocation tree objectid (-9 as u64). A temporary tree used during balance to hold relocated data extents.

ExtentCsum

Extent checksum objectid (-10 as u64). Used as the objectid in EXTENT_CSUM keys in the checksum tree.

FreeSpace

Free space objectid (-11 as u64). Used in the older free space cache (v1) inode items.

FreeIno

Free inode objectid (-12 as u64). Used for free inode number tracking within FS trees.

CsumChange

Checksum change objectid (-13 as u64). Used during online checksum algorithm conversion.

Multiple

Multiple objectids sentinel (-255 as u64). Used internally to indicate that an extent is referenced by multiple trees.

FirstFree

First user-accessible objectid (256). Inode numbers in FS trees start at this value; the root directory inode is always 256.

Id(u64)

A numeric objectid that doesn’t match any well-known value.

Implementations

impl ObjectId

pub fn from_raw(value: u64) -> Self

Convert a raw 64-bit objectid to an ObjectId variant.

pub fn to_raw(self) -> u64

Return the raw u64 objectid value.

pub fn display_with_type(self, key_type: KeyType) -> String

Display an objectid with context-dependent disambiguation.

Some objectid values have different meanings depending on the key type. For example, objectid 1 is ROOT_TREE in general but DEV_ITEMS when used with DEV_ITEM_KEY, and 0 is DEV_STATS when used with PERSISTENT_ITEM_KEY.

pub fn from_tree_name(name: &str) -> Option<Self>

Parse a tree name string (for CLI -t flag) into an ObjectId.

Trait Implementations

impl Clone for ObjectId

fn clone(&self) -> ObjectId

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ObjectId

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for ObjectId

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Hash for ObjectId

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for ObjectId

fn eq(&self, other: &ObjectId) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for ObjectId

impl Eq for ObjectId

impl StructuralPartialEq for ObjectId