Add comprehensive technical analysis documentation for BSR codebase

[Copilot]

Provides in-depth analysis of the BSR (Block Sync & Replication) codebase architecture, covering ~107K LOC across kernel module, user-space utilities, and platform-specific implementations.

Documentation Added

• BSR_CODE_ANALYSIS.md - Complete codebase overview including:

  • Component breakdown: kernel module (62K LOC), user utilities (27K LOC), platform code (13K LOC)
  • Architecture patterns: resource/device/connection hierarchy, state machines, transport abstraction
  • Key differentiators: Stable Sync (1:N topology), Fast Sync (filesystem-aware), Kernel TX Buffering, Passthrough I/O policy
  • Platform implementations: Windows (filter drivers) vs Linux (block device driver)

• BSR_ARCHITECTURE.md - Technical deep-dive with:

  • I/O flow diagrams (write/read paths, request separation)
  • State transition graphs (role, disk, connection states)
  • Synchronization internals (Activity Log, Bitmap, Resync LRU)
  • Performance optimizations (AL/LRU decoupling, separated request queues)
  • Deployment patterns (HA, DR configurations)

Coverage

All major subsystems analyzed:

• Core replication engine (bsr_main.c, bsr_receiver.c, bsr_sender.c)
• State management (bsr_state.c - 196K, handles role/disk/connection transitions)
• Network layer (bsr_transport_tcp.c, abstract transport interface)
• Metadata systems (Activity Log, Bitmap, peer metadata)
• Platform integration (Windows: bsrvflt/bsrfsflt, Linux: bsrhk)
• User tools (bsradm, bsrsetup, bsrmeta with Netlink/IOCTL communication)

Documentation is bilingual (Korean/English) to match repository conventions.

Original prompt

bsr 코드 전반 분석

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