Struct Superblock 

#[non_exhaustive]
pub struct Superblock {

    pub magic: [u8; 8],
    pub csum: [u8; 4],
    pub fsid: [u8; 16],
    pub bytenr: u64,
    pub flags: u64,
    pub generation: u64,
    pub root: u64,
    pub chunk_root: u64,
    pub log_root: u64,
    pub total_bytes: u64,
    pub bytes_used: u64,
    pub root_dir_objectid: u64,
    pub num_devices: u64,
    pub sectorsize: u32,
    pub nodesize: u32,
    pub stripesize: u32,
    pub sys_chunk_array_size: u32,
    pub chunk_root_generation: u64,
    pub compat_flags: u64,
    pub compat_ro_flags: u64,
    pub incompat_flags: u64,
    pub csum_type: CsumType,
    pub root_level: u8,
    pub chunk_root_level: u8,
    pub log_root_level: u8,
    pub label: String,
    pub sys_chunks: Vec<SysChunk>,
    pub crc_valid: Option<bool>,
}

A parsed btrfs superblock — the filesystem geometry, tree-root logical addresses, checksum descriptor, and the decoded sys_chunk_array bootstrap map (the P1 seed for logical→physical translation).

#[non_exhaustive] so later phases add fields without a breaking change.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

magic: [u8; 8]

The 8-byte magic at offset 0x40 — validated to equal BTRFS_MAGIC.

csum: [u8; 4]

csum (offset 0x0) — the first 4 bytes of the 32-byte checksum field (the crc32c digest for a crc32c filesystem), verbatim.

fsid: [u8; 16]

fsid (offset 0x20) — the filesystem UUID.

bytenr: u64

bytenr (offset 0x30) — the physical byte address of THIS superblock copy (65536 for the primary).

flags: u64

flags (offset 0x38).

generation: u64

generation (offset 0x48) — the transaction id this superblock committed (the highest valid copy is the latest committed state — the CoW lever).

root: u64

root (offset 0x50) — logical address of the root tree.

chunk_root: u64

chunk_root (offset 0x58) — logical address of the chunk tree.

log_root: u64

log_root (offset 0x60) — logical address of the log tree (0 = none).

total_bytes: u64

total_bytes (offset 0x70) — filesystem size in bytes.

bytes_used: u64

bytes_used (offset 0x78) — bytes in use.

root_dir_objectid: u64

root_dir_objectid (offset 0x80) — the root directory objectid (6).

num_devices: u64

num_devices (offset 0x88).

sectorsize: u32

sectorsize (offset 0x90) — data block size in bytes.

nodesize: u32

nodesize (offset 0x94) — B-tree node size in bytes.

stripesize: u32

stripesize (offset 0x9c).

sys_chunk_array_size: u32

sys_chunk_array_size (offset 0xa0) — valid byte length of the sys_chunk_array bootstrap region.

chunk_root_generation: u64

chunk_root_generation (offset 0xa4).

compat_flags: u64

compat_flags (offset 0xac).

compat_ro_flags: u64

compat_ro_flags (offset 0xb4).

incompat_flags: u64

incompat_flags (offset 0xbc).

csum_type: CsumType

csum_type (offset 0xc4) — decoded checksum algorithm.

root_level: u8

root_level (offset 0xc6) — B-tree level of the root tree (0 = leaf).

chunk_root_level: u8

chunk_root_level (offset 0xc7) — B-tree level of the chunk tree.

log_root_level: u8

log_root_level (offset 0xc8).

label: String

label (offset 0xab within dev_item… → absolute 0x12b) — the NUL-trimmed filesystem label, lossily decoded from up to 256 bytes.

sys_chunks: Vec<SysChunk>

The decoded sys_chunk_array bootstrap chunk map — the SYSTEM block-group logical→physical entries needed to read the chunk tree in P1. Full chunk-tree walking is P1; P0 decodes the bootstrap structs only.

crc_valid: Option<bool>

The crc32c status of this superblock over its sectorsize-byte block: Some(true) if the stored csum verifies, Some(false) if it does not (corrupt/tampered), or None for a non-crc32c checksum type (deferred). Non-fatal — a bad csum does not fail the parse.

Implementations

impl Superblock

pub fn parse(block: &[u8]) -> Result<Self, BtrfsError>

Parse a btrfs superblock from the start of block.

block must begin at the superblock (the caller slices the 4096-byte block at physical offset 65536; passing the whole sectorsize block lets the crc32c cover the correct range). The magic is validated at offset 0x40 (not 0) — a wrong-image identity error names the offending 8 bytes.

Errors

• BtrfsError::BadMagic if offset 0x40 is not _BHRfS_M — the eight offending bytes are carried in the error.
• BtrfsError::Truncated if block is shorter than the scalar fields.

pub fn fsid_string(&self) -> String

The filesystem UUID rendered as the canonical 8-4-4-4-12 string.

Trait Implementations

impl Clone for Superblock

fn clone(&self) -> Superblock

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Superblock

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

Formats the value using the given formatter.

impl Eq for Superblock

impl PartialEq for Superblock

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for Superblock