Module superblock 

Reading and parsing the btrfs superblock from a block device

The superblock is a 4096-byte structure stored at a fixed offset on disk (primary at 64 KiB, with mirrors at 64 MiB and 256 GiB). It contains the root pointers and metadata needed to bootstrap access to the rest of the filesystem.

Structs

BackupRoot

A single backup root entry from the superblock’s super_roots array.

Superblock

Parsed btrfs superblock.

Enums

ChecksumType

Checksum algorithm used by the filesystem, stored in the superblock’s csum_type field.

Constants

SUPER_MIRROR_MAX

Maximum number of superblock mirrors (3: primary + 2 copies). From kernel-shared/disk-io.h: BTRFS_SUPER_MIRROR_MAX

Functions

csum_superblock

Recompute the checksum of a superblock byte buffer in place.

read_superblock

Read and parse a btrfs superblock from a reader at the given mirror index (0, 1, or 2).

read_superblock_at

Read and parse a btrfs superblock from a reader at an explicit byte offset.

read_superblock_bytes

Read the raw 4096-byte superblock from the primary mirror into a byte buffer.

read_superblock_bytes_at

Read the raw 4096-byte superblock at an explicit byte offset.

super_mirror_offset

Compute the byte offset of the superblock mirror at index.

superblock_generation

Extract the generation field from a raw superblock byte buffer.

superblock_is_valid

Return true if the superblock buffer has valid magic and a matching checksum for whatever algorithm its csum_type field declares.

write_superblock_all_mirrors

Write a superblock buffer to all mirrors that fit within the device.