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Readme3.md

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File System

Complie

Windows

> mingw32-make.exe all

Linux

> make all

Intro

Block array -> Block set -> file -> directory -> file system

  1. Block
    1. balloc() and bfree()
      • Using list or bitmap to manage blocks
    2. bread() and bwrite()
  2. File
  3. Directory

FAT : File Allocation Table

1980s, FAT was introduced. It is just for small files. Free list is used to manage blocks.

// {[data|next],[data,next],.......}
struct block{
    char data[510];
    uint16 next;
}; 

// or 

// {next[0],next[1],.....}  .....  {data[0],data[1],........}
// This is the method that FAT uses.

FAT-12/16/32 (FAT entry, which is size of next pointer in bits)

Command

  • 多用户
    • 登陆
    • 注册
    • logout
  • 文件系统操作
    • open create read write close
    • delete mkdir chdir dir
    • format

EXT2

https://wiki.osdev.org/Ext2#Inode_Type_and_Permissions The root directory is Inode 2.

https://www.vidarholen.net/contents/junk/inodes.html

Note that although both the superblock and the group descriptors are duplicated in each block group, only the superblock and the group descriptors included in block group 0 are used by the kernel, while the remaining superblocks and group descriptors are left unchanged.

get_inode

get_block

get_entry