Module security 

Metadata sync, permissions, ownership, ACL, and xattr operations. Metadata sync, permissions, ownership, xattr operations.

Functions

acquire_mandatory_lock

Acquire an exclusive OFD write lock on the entire file

acquire_read_lock

Acquire a shared OFD read lock on the entire file

apply_metadata

Apply ownership, permissions, timestamps, and sync marker from src to dst

calc_dir_integrity_hash_target

Compute a directory integrity hash from inode metadata and immediate children

canonicalize_safe

Canonicalize path and verify it stays within root. Returns the canonical path or a security error.

check_and_lock_dir_integrity

Acquire a lock and read the directory integrity hash atomically

check_capacity

Return false if available space is below threshold_mb or free inodes are below 1000

check_sync_marker

Verifies if the target has a signature matching the current source state.

copy_timestamps

Copy atime and mtime from src to dst with nanosecond precision via utimensat

create_hard_link

Create a hard link to an existing file

create_mknod

Create a special file (device node, FIFO, socket) via mknod(2)

create_symlink

Create a symbolic link pointing to target

create_version_snapshot

Create a CoW (FICLONE) snapshot of a file for MARS versioning

do_fallocate

Call fallocate(2) on a file with the given mode, offset, and length

enable_compression

Enable filesystem-level compression via FS_IOC_SETFLAGS

enable_f2fs_pinning

Pin a file on F2FS to prevent garbage collection from moving its blocks

get_target_epoch

Read the replication epoch counter from xattr/sidecar metadata

get_valid_dir_hash

Get the stored directory integrity hash, returning 0 if stale or missing

ioctl_ficlone

Clone a file via FICLONE ioctl (CoW reflink from src_fd to a new file at dst_path)

is_dir_metadata_synced

Check if directory metadata (uid, gid, mode, mtime) matches between src and dst

is_filesystem_compressed

Check if the filesystem at path uses transparent compression (btrfs or F2FS)

open_beneath

Open a file beneath root using openat2(2) with RESOLVE_BENEATH. The kernel rejects any path that escapes root via .. or symlinks. Falls back to canonicalize_safe + standard open if openat2 unavailable.

path_within_root

Check that path is within root after canonicalization. Rejects symlinks that escape the root directory.

preallocate

Preallocate disk space with FALLOC_FL_KEEP_SIZE (best-effort, ignores errors)

probe_direct_io

Probe whether the filesystem supports O_DIRECT by writing a test block

probe_rwf_uncached

Probe whether the kernel supports RWF_UNCACHED via io_uring registered buffer read

probe_xattr_support

Probe whether the filesystem at target_root supports extended attributes

revert_snapshot

Revert a file to a previous snapshot version by copying the version file over the live path.

set_file_attr

Set filesystem inode flags via FS_IOC_SETFLAGS (e.g. immutable, append-only)

set_ownership

Set file ownership (uid/gid) via chown

set_project_id

Set the XFS/ext4 project ID for directory quota tracking

sync_xattrs

Copy all extended attributes from src to dst (best-effort, ignores errors)

truncate_file

Truncate or extend a file to the specified size

write_dir_integrity_hash

Write a directory integrity hash with mtime guard for staleness detection