xv6-riscv-kernel/kernel/fs.h

#pragma once

#include "types.h"

// On-disk file system format.
// Both the kernel and user programs use this header file.

#define ROOTINO 1    // root i-number
#define BSIZE   1024 // block size

// Disk layout:
// [ boot block | super block | log | inode blocks |
//                                          free bit map | data blocks]
//
// mkfs computes the super block and builds an initial file system. The
// super block describes the disk layout:
struct superblock {
  u32 magic;      // Must be FSMAGIC
  u32 size;       // Size of file system image (blocks)
  u32 nblocks;    // Number of data blocks
  u32 ninodes;    // Number of inodes.
  u32 nlog;       // Number of log blocks
  u32 logstart;   // Block number of first log block
  u32 inodestart; // Block number of first inode block
  u32 bmapstart;  // Block number of first free map block
};

#define FSMAGIC 0x10203040

#define NDIRECT   12
#define NINDIRECT (BSIZE / sizeof(u32))
#define MAXFILE   (NDIRECT + NINDIRECT)

// On-disk inode structure
struct dinode {
  short type;               // File type
  short major;              // Major device number (T_DEVICE only)
  short minor;              // Minor device number (T_DEVICE only)
  short nlink;              // Number of links to inode in file system
  u32   size;               // Size of file (bytes)
  u32   addrs[NDIRECT + 1]; // Data block addresses
};

// Inodes per block.
#define IPB (BSIZE / sizeof(struct dinode))

// Block containing inode i
#define IBLOCK(i, sb) ((i) / IPB + sb.inodestart)

// Bitmap bits per block
#define BPB (BSIZE * 8)

// Block of free map containing bit for block b
#define BBLOCK(b, sb) ((b) / BPB + sb.bmapstart)

// Directory is a file containing a sequence of dirent structures.
#define DIRSIZ 14

struct dirent {
  u16  inum;
  char name[DIRSIZ];
};