Crate btrfs_uapi 

btrfs-uapi: typed Rust wrappers around the btrfs kernel interface

This crate provides typed, safe access to the btrfs kernel interface. Kernel communication uses two mechanisms:

• ioctls for most operations (balance, scrub, subvolume management, …)
• sysfs under /sys/fs/btrfs/<uuid>/ for status that the kernel does not expose via ioctl (quota state, commit statistics, scrub speed limits)

Safety

All unsafe code is confined to the raw module, which contains bindgen-generated types from the kernel UAPI headers (btrfs.h and btrfs_tree.h) and nix ioctl macro declarations for every BTRFS_IOC_* call.

Every other module wraps raw into a public API that is entirely safe, exposes no kernel types, and uses idiomatic Rust types throughout: BorrowedFd, Uuid, bitflags, SystemTime, CString, and so on.

Usage

Every function that issues an ioctl takes a BorrowedFd open on any file within the target btrfs filesystem. Functions in sysfs instead take a uuid::Uuid, which can be obtained from filesystem::filesystem_info.

Most ioctl-based operations require CAP_SYS_ADMIN.

Portability

btrfs is Linux-only; this crate does not support other operating systems. Some ioctls used here were introduced in relatively recent kernel versions; this crate targets modern kernels (5.x and later) and does not attempt to detect or work around missing ioctls on older kernels. It is only tested on amd64, but all architectures supported by the kernel (and Rust) should work.

Modules

balance

Balance operations: redistributing data and metadata across devices

blkdev

Block device ioctls: BLKGETSIZE64, BLKDISCARD

chunk

Per-device physical allocation data from the chunk tree

defrag

File defragmentation: rewriting fragmented extents into contiguous runs

device

Device management: adding, removing, querying, and extent layout

fiemap

Physical extent layout of files via FS_IOC_FIEMAP

filesystem

Filesystem-level operations: metadata, sync, label, and resize

inode

Inode and path resolution: mapping between inodes, logical addresses, and paths

quota

Quota and qgroup management: enabling quotas and tracking disk usage

raw

Raw bindgen output and ioctl declarations for the btrfs UAPI

replace

Device replacement: replacing a device with another while the filesystem is online

scrub

Data integrity scrubbing: verifying and repairing filesystem checksums

send_receive

Send and receive: generating and applying btrfs send streams

space

Block group space usage: how much space each chunk type allocates and uses

subvolume

Subvolume and snapshot management: creating, deleting, and querying subvolumes

sysfs

Sysfs interface: reading filesystem and device state from /sys/fs/btrfs/

tree_search

Generic B-tree search: walking any internal btrfs tree via BTRFS_IOC_TREE_SEARCH

Macros

field_size

Return the size in bytes of a single field within a struct.