Design And Implementation Of Embedded File System Based On NAND Flash

The file system is an important part of the embedded system.It is a way to organize files on storage devices and provides users with a file and directory-based storage mechanism.The file system is responsible for scheduling and managing file storage space and storing data in external storage media.The embedded file system has the characteristics of strong stability,high real-time and streamlined efficiency.The research in this thesis is an embedded file system based on NAND Flash.There are many NAND Flash-based file systems commonly used in wireless broadband products,such as YAFFS2,JFFS2,UBIFS,etc.,but these file systems require at least 3M NAND partition capacity.Because there are some small partitions on the product,the data stored in these small partitions is very small,and the usable limit size is 1M.If these file systems are mounted,space will be wasted.For products with tight NAND Flash space,there is a need to reduce the size of the partition.Therefore,a simple and reliable file system is developed for a large number of small files and small partitions,and the operation of files and directories is externally presented.The implementation of this file system is at the kernel file system level,using the VFS(virtual file system)framework to ensure that users cannot see the internal data structure and management.For users,it is sufficient to operate files in accordance with the Linux system.According to functions,the file system is divided into seven modules: block and page management module,file management module,VFS module,read-write cache module,partition mount module,garbage collection module,and NAND Flash IO module.This thesis mainly introduces the block and page management module,file management module and VFS module in detail.The block and page management module is mainly responsible for reading and writing the blocks and pages of the NAND Flash storage device,managing the usage information of all physical blocks in the partition,allocating storage space,and managing bad blocks;the file management module is mainly responsible for realizing the operation of the file structure,Including the file structure design,the mapping of the physical address and the logical address of the data storage,and the operation of the file structure;the VFS module is mainly responsible for using the VFS framework to implement specific file functions and provide users with a unified interface.This thesis designs different test cases for the embedded file system based on NAND Flash,and carries on the performance test to the system.The test results show that the various functional modules of the system are operating normally,and that each function has met the demand expectations and has been applied in actual products.