1 // On-disk file system format. 2 // Both the kernel and user programs use this header file. 3 4 5 #define ROOTINO 1 // root i-number 6 #define BSIZE 512 // block size 7 8 // Disk layout: 9 // [ boot block | super block | log | inode blocks | 10 // free bit map | data blocks] 11 // 12 // mkfs computes the super block and builds an initial file system. The 13 // super block describes the disk layout: 14 struct superblock { 15 uint size; // Size of file system image (blocks) 16 uint nblocks; // Number of data blocks 17 uint ninodes; // Number of inodes. 18 uint nlog; // Number of log blocks 19 uint logstart; // Block number of first log block 20 uint inodestart; // Block number of first inode block 21 uint bmapstart; // Block number of first free map block 22 }; 23 24 #define NDIRECT 12 25 #define NINDIRECT (BSIZE / sizeof(uint)) 26 #define MAXFILE (NDIRECT + NINDIRECT) 27 28 // On-disk inode structure 29 struct dinode { 30 short type; // File type 31 short major; // Major device number (T_DEV only) 32 short minor; // Minor device number (T_DEV only) 33 short nlink; // Number of links to inode in file system 34 uint size; // Size of file (bytes) 35 uint addrs[NDIRECT+1]; // Data block addresses 36 }; 37 38 // Inodes per block. 39 #define IPB (BSIZE / sizeof(struct dinode)) 40 41 // Block containing inode i 42 #define IBLOCK(i, sb) ((i) / IPB + sb.inodestart) 43 44 // Bitmap bits per block 45 #define BPB (BSIZE*8) 46 47 // Block of free map containing bit for block b 48 #define BBLOCK(b, sb) (b/BPB + sb.bmapstart) 49 50 // Directory is a file containing a sequence of dirent structures. 51 #define DIRSIZ 14 52 53 struct dirent { 54 ushort inum; 55 char name[DIRSIZ]; 56 }; 57 58