Draft: libdm refactor: consolidate device_mapper and base directories into libdm

libdm refactor: consolidate device_mapper and base directories into libdm

Overview

This merge request implements a major refactoring of the LVM2 codebase to consolidate the device_mapper and base directories into the existing libdm directory. This consolidation simplifies the codebase structure, reduces duplication, and provides a cleaner API surface for device mapper functionality.

Summary of Changes

The refactoring consists of 22 commits that systematically:

1. Sync existing libdm components with their device_mapper counterparts to ensure feature parity
2. Add missing functionality from device_mapper to libdm (RAID, VDO, integrity, cache, writecache)
3. Consolidate base directory utilities (hash, radix tree, container_of) into libdm
4. Remove redundant directories (device_mapper and base) after successful migration
5. Update all references throughout the codebase to use the consolidated libdm API

Key Changes

New Functionality Added to libdm:

• RAID support: Added RAID target functionality with dm_raid_count_failed_devices and dm_raid_clear_failed_devices functions
• VDO support: Integrated VDO target functionality for data deduplication
• Integrity support: Added integrity target functionality for data integrity checking
• Cache/Writecache support: Integrated cache and writecache target functionality
• Enhanced data structures: Added radix tree implementation and updated hash implementation
• Utility functions: Added dm_container_of macro and dm_active_device support

Code Consolidation:

• Removed ~26,000 lines of duplicated code from device_mapper and base directories
• Added ~2,000 lines of consolidated functionality to libdm
• Updated 158 files across the codebase to use the new libdm API
• Maintained backward compatibility through proper function naming and API design

API Improvements:

• All device mapper functionality now accessible through a single libdevmapper.h header
• Consistent naming convention with dm_ prefix for all functions
• Cleaner separation of concerns within the libdm directory structure
• Enhanced logging and debugging capabilities

Benefits

1. Simplified maintenance: Single source of truth for device mapper functionality
2. Reduced code duplication: Eliminated redundant implementations across directories
3. Better API design: Consistent interface through libdm
4. Easier testing: Consolidated test suite for all device mapper functionality
5. Improved build system: Simplified Makefile structure and dependencies

Testing

The refactoring maintains full backward compatibility and all existing functionality. The changes have been tested to ensure:

• All LVM2 commands continue to work as expected
• Device mapper operations function correctly
• No regressions in existing functionality
• Proper compilation across different build configurations

mpact

This refactoring represents a significant step forward in code organization and maintainability for the LVM2 project, providing a solid foundation for future development while maintaining full backward compatibility.

---

Type: Refactoring
Scope: libdm consolidation
Breaking Changes: None (backward compatible)
Files Changed: 158 files
Lines Added: ~2,000
Lines Removed: ~26,000