日志文件系统在嵌入式存储设备上的设计和实现

【作者】 郑良辰；

【导师】 孙玉芳；

【作者基本信息】 中国科学院软件研究所 ， 计算机软件与理论， 2001， 硕士

【摘要】 对嵌入式系统来说，非正常断电随时可能发生，它会导致文件系统不一致 性，带来文件系统的破坏和信息的丢失。因此，在嵌入式存储设备上，设计实 现一种特殊的防断电文件系统具有特别重要的意义。日志文件系统通过记日志 的方法来防止文件系统的异常破坏，正是我们需要的防断电文件系统。 本文首先介绍了几种不同类型日志文件系统并比较了它们的优劣。结合这 些分析，我们讨论了特殊日志文件系统JFFS的设计思想和层次结构；JFFS考 虑了嵌入式存储设备Flash 的特殊属性，实现了一种简化设计的 Log-Structured日志文件系统，是嵌入式存储设备上防断电文件系统的理想选 择。最后，本文着重阐述了在特殊存储设备DiskOnChip上JFFS的实现，主要 讨论了DiskOnChip驱动对JFFS不支持问题的解诀以及JFFS和普通文件系统在 一块DiskOnChip上共存的存储方案的实现。目前，JFFS已成为红旗嵌入式存 储方案的重要组成部分。将来，随着我们对JFFS的进一步完善，JFFS必然会 在嵌入式产品中得到越来越广泛地应用。更多还原

【Abstract】 In embedded systems, unexpected power-off often occurs. For a normal kind of filesystem, unexpected power-off often causes the corruption of the file system and the lose ofdata. T fore, it is very important to design and implement a special kind of file system topreven such corruption. Journaling File System is just such kind file system we need.In this paper, we firstly compare several kinds of journaling file systems and point out thedefference between them. On the base of analysis above, we discuss the design and layout ofJFFS, a special journaling file system. In consideration of small size and special read-writecharacters of Flash devices, JFFS is designed as a simplified kind of log-structured jounaling filesystem, which have good performance to prevent corruption caused by unexpected power-off.At the last part of the paper, we put emphasis on JFFS’ implementaion on DistOnChip, aspecial kind of embedded memory devcie. We successfully solve the problem that the dirver ofDiskOnChip support JFFS, bring forward and implement a memory plan in which JFFS andother normal file systems can exist on a DiskOnChip at the same time, and make JFFS turn intoa important part of Red Flag Embedded Memory Plan. In future, with its further devolopment,JFFS will be used far and wide.更多还原