Embedded System Lab.

Embedded System Lab.최 진 화

Kilmo Choirlfah926@naver.com

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A Study of Linux File System Evolution

L. Lu, A. C. Arpaci-Dusseau, R. H. ArpaciDusseau, S. Lu

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Index

Introduction

Patch Overview

File System Bugs

Performance and Reliability

Conclusion

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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.

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Patch Overview Investigate general questions regarding file-system patches

patch type, patch trend, patch size

Patch Type

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Patch Overview Patch Trend

While the number of patches per version increased in general, the per-

centage of patch type relatively stable

Bug patches do not decrease over time

Patch Size

Way to quantify the complexity of patch

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File System Bugs Correlation Between Code and Bugs

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File System Bugs Bug Patterns and Trends

Fine-grained bug patterns provide useful information to developer and tool builders

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File System Bugs Bug Consequence

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File System Bugs Bug Pattern Examples and Analysis

Semantic Bugs

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File System Bugs Concurrency Bugs

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File System Bugs Memory Bugs

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File System Bugs Error Code Bugs

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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

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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

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Conclusion 5079 patches across six linux file system

Nearly 1800 bugs

“Software archeology”

Should be of utility to file-system developers and tool makers