slmkfs/fsformat.h

// This is NEW CODE to replace old fs.h header, defining on-disk filesystem
// layout used by mkfs and the kernel.
#ifndef _FSFORMAT_H
#define _FSFORMAT_H

typedef unsigned int fsformat_uint32_t;
typedef long long fsformat_int64_t;
typedef unsigned short fsformat_uint16_t;
typedef short fsformat_int16_t;

typedef struct fsformat_superblock fsformat_superblock_t;
typedef struct fsformat_inode fsformat_inode_t;
typedef struct fsformat_dirent_v0 fsformat_dirent_v0_t;
typedef struct fsformat_dirent_v1 fsformat_dirent_v1_t;

// The "old" magic number is used to mark "version 0" or xv6-compatible
// filysystems.
#define FSFORMAT_MAGIC_OLD    0x10203040
// The "new" magic number is used to mark filesystems which are above
// or equal to "version 1". These share the same superblock structure
// except with extended fields and options.
#define FSFORMAT_MAGIC_NEW    0x102030F0

struct fsformat_superblock {
  // The first eight fields are compatible with xv6 filesystem (provided
  // that the block size etc. match your fork of xv6!)
  
  fsformat_uint32_t magic;
  fsformat_uint32_t totalblocks;
  fsformat_uint32_t datablocks;
  fsformat_uint32_t inodelimit;
  fsformat_uint32_t logblocks;
  fsformat_uint32_t firstlogblock;
  fsformat_uint32_t firstinodeblock;
  fsformat_uint32_t firstbitmapblock;
  
  // The rest of the fields will only be usable if the "magic" field is
  // equal to FSFORMAT_MAGIC_NEW. These are partly used to detect or
  // confirm filesystem settings such as block size.
  
  // Simple version number & FLAGS. The lower 8 bits is used for
  // the simple version (e.g. 1 for version 1), the upper 24 bits may
  // be used for additional flags, minor versions etc. in later versions
  // but are set to zero for version 1.
  fsformat_uint32_t extd_versionflags;    
  // Block size in bytes.
  fsformat_uint32_t extd_blocksize;
  // Superblock structure size in bytes (i.e. to detect which extended
  // fields are usable.
  fsformat_uint32_t extd_superblocksize;
  // Inode structure size.
  fsformat_uint32_t extd_inodestructsize;
  // Filename length.
  fsformat_uint32_t extd_filenamesize;
  // Inode reference size. Either set to 2 or 4, or special numbers for
  // other special formats in the future.
  fsformat_uint32_t extd_inoderefsize;
  
  // Number of direct blocks per inode for storing data in the first
  // few blocks of a file.
  fsformat_uint32_t extd_directblocks;
  // Number of indirect blocks per inode for storing additional data of
  // large files
  fsformat_uint32_t extd_indirectblocks;
};

#define FSFORMAT_DIRECTBLOCKS 12

struct fsformat_inode {
  fsformat_int16_t type;
  fsformat_int16_t device_major;
  fsformat_int16_t device_minor;
  fsformat_int16_t linkcount;
  fsformat_uint32_t totalbytes;
  fsformat_uint32_t addrs[FSFORMAT_DIRECTBLOCKS + 1];
};

#define FSFORMAT_NAMESIZE_OLD 14

struct fsformat_dirent_v0 {
  fsformat_uint16_t inodenumber;
  char filename[FSFORMAT_NAMESIZE_OLD];
};

#define FSFORMAT_NAMESIZE_NEW 120

struct fsformat_dirent_v1 {
  fsformat_uint32_t datainode;
  fsformat_uint32_t metainode;
  char filename[FSFORMAT_NAMESIZE_NEW];
};


// The "big" dirent structure is used for conveying dirent information
// to userland, and so allows exceptionally large name sizes and dir
// info. This isn't really implemented yet but can be for consistency.
#define FSFORMAT_NAMESIZE_BIG 2032

struct fsformat_dirent_big {
  fsformat_int64_t datainode;
  fsformat_int64_t metainode;
  char filename[FSFORMAT_NAMESIZE_BIG];
};

// From ifndef at top of file:
#endif