Module overlayfs

OverlayFS v2 - Overlay filesystem implementation for VFS v2

This module provides a union/overlay view of multiple filesystems, allowing files and directories from multiple source filesystems to appear as a single unified filesystem hierarchy.

Features

• Multi-layer support: Combines an optional upper layer (read-write) with multiple lower layers (read-only) in priority order
• Copy-up semantics: Modifications to lower layer files are copied to the upper layer before modification
• Whiteout support: Files can be hidden or deleted from view using special whiteout entries
• Mount point aware: Handles crossing mount boundaries correctly when resolving paths across layers

Usage

// Create overlay with upper and lower layers
let overlay = OverlayFS::new(
    Some((upper_mount, upper_entry)),  // Upper layer for writes
    vec![(lower_mount, lower_entry)],  // Lower layers (read-only)
    "my_overlay".to_string()
)?;

Cross-VFS Support

• Cross-VFS overlays supported: Upper and lower layers can come from different VFS managers, enabling flexible overlay configurations
• Seamless integration: Mount points from different VFS managers are unified transparently through the overlay interface

Limitations

• Upper layer is required for write operations
• Whiteout files follow the .wh.filename convention

Structs

OverlayDirectoryObject

File object for OverlayFS directory operations

OverlayFS

OverlayFS implementation for VFS v2

OverlayFSDriver

Driver for creating OverlayFS instances

OverlayNode

A composite node that represents a file/directory across overlay layers

Statics

__DRIVER_INITCALL__ 🔒

Functions

register_driver 🔒

Register the OverlayFS driver with the filesystem driver manager