1. Embedded System Lab. 최 진 화최 진 화 Kilmo Choi rlfah926@naver.com 최길모 A Study of Linux File System Evolution L. Lu, A. C. Arpaci-Dusseau, R. H. ArpaciDusseau, S. Lu

2. Embedded System Lab. 최 길 모최 길 모 Index Introduction Patch Overview File System Bugs Performance and Reliability Conclusion

3. Embedded System Lab. 최 길 모최 길 모 Introduction Open-source local file-systems remain a critical component in the world of modern storage(ex. Distributed file system, Smart phone) Target file-systems  Every file-system in Linux 2.6 series(2.6.0~2.6.39) over a period of 8 years including 5079 patches  Ext3, Ext4, XFS, Btrfs, ReiserFS, JFS Patches category  Bug, performance, reliability, etc.

4. Embedded System Lab. 최 길 모최 길 모 Patch Overview Investigate general questions regarding file-system patches  patch type, patch trend, patch size Patch Type

5. Embedded System Lab. 최 길 모최 길 모 Patch Overview Patch Trend  While the number of patches per version increased in general, the percentage of patch type relatively stable  Bug patches do not decrease over time Patch Size  Way to quantify the complexity of patch

6. Embedded System Lab. 최 길 모최 길 모 File System Bugs Correlation Between Code and Bugs

7. Embedded System Lab. 최 길 모최 길 모 File System Bugs Bug Patterns and Trends  Fine-grained bug patterns provide useful information to developer and tool builders

8. Embedded System Lab. 최 길 모최 길 모 File System Bugs Bug Consequence

9. Embedded System Lab. 최 길 모최 길 모 File System Bugs Bug Pattern Examples and Analysis  Semantic Bugs

10. Embedded System Lab. 최 길 모최 길 모 File System Bugs  Concurrency Bugs

11. Embedded System Lab. 최 길 모최 길 모 File System Bugs  Memory Bugs

12. Embedded System Lab. 최 길 모최 길 모 File System Bugs  Error Code Bugs

13. Embedded System Lab. 최 길 모최 길 모 Performance and Reliability Performance Patches  Synchronization Inefficient usage of synchronization methods removing unnecessary locks, using smaller locks  Access Optimization Apply smarter access strategies caching metadata and statistics, avoiding unnecessary I/O and computing  Schedule Improve I/O operation scheduling batching writes, opportunistic readhead

14. Embedded System Lab. 최 길 모최 길 모 Performance and Reliability Reliability  Robust Enhance file-system robustness boundary limits and access permission checking  Corruption Defense Improve file systems ability to handle various possible corruption  Error Enhancement Improve original error handling  Annotation user/kernel space pointer and lock annotation for early bug detection  Debug Add more internal debugging or tracing support

15. Embedded System Lab. 최 길 모최 길 모 Conclusion 5079 patches across six linux file system Nearly 1800 bugs “Software archeology” Should be of utility to file-system developers and tool makers